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Matter Loops Corrected Modified Gravity in Palatini Formulation

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Communications in Theoretical Physics 2008年第7期50卷 275-278页

作者： meng xin-He WANG Peng Department of Physics Nankai University Tianjin 300071 China Department of Physics and SLAC Stanford University California USA BK21 Division of Advanced Research and Education in Physics Department of Physics Hanyang University Seoul 133 791 Korea

Recently,corrections to the standard Einstein Hilbert action were proposed to explain the current cosmicacceleration in stead of introducing dark *** the Palatini formulation of those modified gravity models,thereis an important observation due to Arkani Hamed:matter loops will give rise to a correction to the modified gravityaction proportional to the Ricci scalar of the *** the presence of such a term,we show that the current formsof modified gravity models in Palatini formulation,specifically,the 1/R gravity and in R gravity,will have *** we study the possible instabilities due to the presence of phantom *** show that the strong instability inthe metric formulation of 1/R gravity indicated by Dolgov and Kawasaki will not appear and the decay timescales forthe phantom fields may be long enough for the theories to make sense as effective field *** the other hand,if wechange the sign of the modification terms to eliminate the phantoms,some other inconsistencies will arise for the variousversions of the modified gravity ***,we comment on the universal property of the Palatini formulation ofthe matter loops corrected modified gravity models and its implications.

关键词： modified gravity accelerated cosmic expansion loop correction and dark energy

Restoring cosmological concordance with axion-like early dark energy and dark matter characterized by a constant equation of state?

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Communications in Theoretical Physics 2024年第7期76卷 74-82页

作者： Yan-Hong Yao xin-He meng School of Physics and Astronomy Sun Yatsen University 2 Daxue RoadTangjiaZhuhaiChina School of Physics Nankai University 94 Weijin RoadNankaiTianjinChina

The Hubble tension persists as a challenge in *** early dark energy(EDE)models,initially considered the most promising for alleviating the Hubble tension,fall short of addressing the issue without exacerbating other tensions,such as the S_(8)*** that a negative dark matter(DM)equation of state(EoS)parameter is conducive to reduce the value of the σ_(8)parameter,we extend the axion-like EDE model in this paper by replacing the cold dark matter(CDM)with DM characterized by a constant EoS w_(dm)(referred to as WDM hereafter).We then impose constraints on this axion-like EDE extension model,along with three other models:the axion-like EDE model,ΛWDM,and Λ*** constraints are derived from a comprehensive analysis incorporating data from the Planck 2018 cosmic microwave background,baryon acoustic oscillations,and the Pantheon compilation,as well as a prior on H_(0)(i.e.H_(0)=73.04±1.04,based on the latest local measurement by Riess et al)and a Gaussianized prior on S_(8)(i.e.S_(8)=0.766±0.017,determined through the joint analysis of KID1000+BOSS+2dLenS).We find that although the new model maintains the ability to alleviate the Hubble tension to~1.4σ,it still exacerbates the S_(8)tension to a level similar to that of the axion-like EDE model.

关键词： Hubble tension early dark energy noncold dark matter S8 tension

Global Mittag-Leffler stability for fractional-order coupled systems on network without strong connectedness

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Science China(Information Sciences) 2020年第3期63卷 184-194页

作者： xin meng Yonggui KAO Hamid Reza KARIMI Cunchen GAO School of Mathematical Sciences Ocean University of China Department of Mechanical Engineering Politecnico di Milano Department of Mathematics Harbin Institute of Technology (Weihai)

This study investigates the global Mittag-Leffler stability(MLS) problem of the equilibrium point for a new fractional-order coupled system(FOCS) on a network without strong connectedness. In particular, an integer-order coupled system is extended into the FOCS on a complex network without strong connectedness. Based on the theory of asymptotically autonomous systems and graph theory, sufficient conditions are derived to ensure the existence, uniqueness, and global MLS of the solutions of this FOCS on a network. Finally, a numerical example is provided to demonstrate the validity and potential of the proposed method for studying the MLS of FOCSs.

关键词： global Mittag-Leffler stability fractional-order coupled system connectedness

Dynamical behavior of a delayed prey-predator-scavenger system with fear effect and linear harvesting

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International Journal of Biomathematics 2021年第4期14卷 159-188页

作者： xin-You meng Jie Li School of Science Lanzhou University of Technology LanzhouGansu 730050P.R.China College of Technology and Engineering Lanzhou University of Technology Lanzhou Gansu 730050P.R.China

In this paper,we propose a delayed prey-predator-scavenger system with fear effect and linear ***,we discuss the existence and stability of all possible ***,we investigate the existence of Hopf bifurcation of the delayed system by regarding the gestation period of the scavenger as a bifurcation ***,we obtain the direction of Hopf bifurcation and the stability of bifurcating periodic solutions by using the normal form theory and the central manifold *** addition,we give the optimal harvesting strategy of the delayed system based on Pontryagin's maximum principle with ***,some numerical simulations are carried out to verify our theoretical results.

关键词： Prey-predator-scavenger fear effect time delay Hopf bifurcation optimal harvesting policy

功能性踝关节不稳男性下蹲跳过程中下肢的生物力学特征

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中国组织工程研究 2025年第3期29卷 478-485页

作者：王子龙孟昕张芷棋谢雨孟令越张秋霞孔翎宇苏州大学体育学院江苏省苏州市215000

背景:踝关节作为人体的末端承重关节,承受着机体自上而下的压力,这导致踝关节在运动中很容易发生损伤,诱发功能性踝关节不稳,对日常生活造成负面影响。研究功能性踝关节不稳患者在下蹲跳过程中的下肢生物力学表现,对实现科学训练、预防... 详细信息

背景:踝关节作为人体的末端承重关节,承受着机体自上而下的压力,这导致踝关节在运动中很容易发生损伤,诱发功能性踝关节不稳,对日常生活造成负面影响。研究功能性踝关节不稳患者在下蹲跳过程中的下肢生物力学表现,对实现科学训练、预防踝关节损伤以及伤后临床康复提供理论参考具有重要意义。目的:探究功能性踝关节不稳患者下蹲跳过程中的下肢运动学与动力学特征。方法:于2023年3-9月在苏州大学招募男性功能性踝关节不稳患者与健康人群各15名,年龄22-28岁,所有受试者均完成下蹲跳试验。采用Vicon红外高速运动捕捉系统和Kistler三维测力台对两组受试者在下蹲跳起跳阶段、离地瞬间时刻、初始着地时刻和垂直地面反作用力峰值时刻的下肢运动学和动力学指标进行同步采集及对比分析。结果与结论:(1)离地瞬间时刻,与健康对照组的匹配侧相比,功能性踝关节不稳组患侧显示出了更小的膝关节内旋力矩(P=0.020)、更小的踝关节内旋力矩(P=0.009)。(2)落地瞬间时刻,与健康对照组的匹配侧相比,功能性踝关节不稳组患侧显示出了更小的髋关节屈曲角度(P=0.039);功能性踝关节不稳组相较于健康对照组显示出了更小的髋关节外展角度(P=0.022)、更小的膝关节内翻角度(P=0.010)、更大的膝关节外旋角度(P=0.021)、更小的踝关节内翻角度(P=0.004)、更小的踝关节外旋角度(P=0.008)。(3)垂直地面反作用力峰值时刻,功能性踝关节不稳组相较于健康对照组显示出了更小的踝关节内翻角度(P=0.044);(4)结果说明,功能性踝关节不稳者在下蹲跳动作中相较于健康人群存在异常的下肢生物力学特征,主要表现为离地与落地瞬间时刻,下肢关节在矢状面和额状面的运动学和动力学指标变化。这些改变反映出功能性踝关节不稳人群在执行下蹲跳时采用了僵硬的起跳与着陆模式,倾向于将患侧踝关节负荷转移至下肢其他关节,并显示出健侧下肢的代偿现象。因此,检测和纠正异常生物力学特征应该成为功能性踝关节不稳者康复训练的一部分。

关键词：功能性踝关节不稳下蹲跳生物力学运动学参数动力学参数

High-resolution simulation of upper-ocean submesoscale variability in the South China Sea:Spatial and seasonal dynamical regimes

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Acta Oceanologica Sinica 2022年第7期41卷 26-41页

作者： Haijin Cao xin meng Zhiyou Jing Xiaoxiao Yang Key Laboratory of Marine Hazards Forecasting of Ministry of Natural Resources Hohai UniversityNanjing210024China College of Oceanography Hohai UniversityNanjing210024China State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou510301China

Submesoscale processes in marginal seas usually have complex generating mechanisms,highly dependent on the local background flow and *** numerical study investigates the spatial and seasonal differences of submesoscale activities in the upper ocean of the South China Sea(SCS)and the different dynamical regimes for *** spatial and seasonal variations of vertical vorticity,horizontal convergence,lateral buoyancy gradient,and strain rate are analyzed to compare the submesoscale phenomenon within four sub-regions,the northern region near the Luzon Strait(R1),the middle ocean basin(R2),the western SCS(R3),and the southern SCS(R4).The results suggest that the SCS submesoscale processes are highly heterogeneous in space,with different seasonalities in each *** submesoscale activities in the northern sub-regions(R1,R2)are active in winter but weak in summer,while there appears an almost seasonal anti-phase in the western region(R3)compared to R1 and ***,no clear seasonality of submesoscale features is shown in the southern region(R4).Further analysis of Ertel potential vorticity reveals different generating mechanisms of submesoscale processes in different *** analyses also show the vertical extent of vertical velocity and the role of monsoon in generating submesoscale activities in the upper ocean of *** these results suggest that the sub-regions have different regimes for submesoscale processes,e.g.,Kuroshio intrusion(R1),monsoon modulation(R2),frontal effects(R3),topography wakes(R4).

关键词： submesoscale South China Sea high-resolution simulation spatial difference seasonal difference

Analysis of a delayed diffusive model with Beddington-DeAngelis functional response

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International Journal of Biomathematics 2019年第4期12卷 277-300页

作者： xin-You meng Jiao-Guo Wang School of Science Lanzhou University of Technology Lanzhou Gansu 730050 P. R.China

In this paper, a delayed diffusive phytoplankton-zooplankton model with Beddington DeAngelis functional response and toxins is investigated. Existence of equilibria of the system are solved. The global asymptotic stability of the zooplankton-free equilibrium is obtained. The local stability of the coexistent equilibrium and existence of Hopf bifurcation are discussed. In addition, the properties of the Hopf bifurcation are studied based on the center manifold and normal form theory for partial differential equations. Finally, some numerical simulations are also carried out to confirm our theoretical analysis.

关键词： Phytoplankton-zooplankton time delay stability Hopf bifurcation diffusive Beddington-DeAngelis

Effect of Ultraviolet Aging on the Bonding and Tensile Properties of Polymer-Cement Composite

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Journal of Renewable Materials 2021年第6期9卷 1157-1168页

作者： Zhihang Wang Jinyu Xu xin meng Congjin Zhu Air Force Engineering University Xi’an710038China Northwest Polytechnic University Xi’an710072China

In this paper,the specimens of polymer-cement composites after 1 d,7 d,15 d,and 30 d aging without aging and UV aging are subjected to fixed extension test and tensile *** observing the mode of the composite in the fixed-elongation test,and measuring the elastic recovery rate,tensile strength,elongation at break,peak tensile strain,tensile toughness and pre-peak tensile toughness of the composite,the effects of UV aging on the bonding and the tensile properties of the composite were *** combining with scanning electron microscopy experiments,the micro-mechanism of the effect of ultraviolet aging on the properties of composite was *** results showed that the composite had a good bonding property,and no damage was observed after UV aging for 30 *** UV aging increased the elastic recovery rate and peak tensile within a certain *** elastic recovery rate and peak tensile strain of the composite increased by 6.60%and 23.55%respectively after UV aging for 15 ***,the UV aging could enhance the tensile property and the tensile energy consumption performance of the *** tensile strength of the composite increased by 65.36%after UV aging for 30 *** tensile toughness and pre-peak tensile toughness of the composite were increased by 43.29%and 101.83%respectively after UV aging for 15 *** elongation at break of composite decreased continuously after UV aging due to the photo-oxygen reaction,as well as secondary hydration reaction and cross-linking curing reaction of cement.

关键词： Polymer-cement composite ultraviolet aging bonding property tensile property failure mode microstructure

Friedmann Cosmology with Bulk Viscosity:A Concrete Model for Dark Energy

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Communications in Theoretical Physics 2009年第8期52卷 377-382页

作者： meng xin-He D0U Xu Department of Physics Nankai University Tianjin 300071 China Kavli Institute for Theoretical Physics China at the Chinese Academy of Sciences （KITPC-CAS） Beijing 100190 China

The universe content is considered as a non-perfect fluid with bulk viscosity and can be described by a general equation of state （endowed some deviation from the conventionally assumed cosmic perfect fluid model）. An explicitly bulk viscosity dark energy model is proposed to confront consistently with the current observational data sets by statistical analysis and is shown consistent with （not deviated away much from） the concordant A Cold Dark Matter （CDM） model by comparing the decelerating parameter. Also we compare our relatively simple viscosity dark energy model with a more complicated one by contrast with the concordant ACDM model and find our model improves for the viscosity dark energy model building. Finally we discuss the perspectives of dark energy probes for the coming years with observations.

关键词： dark energy cosmology bulk viscosity unification of dark matter and dark energy