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On the gauge dependence of scalar induced secondary gravitational waves during radiation and matter domination eras

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Science China(Physics,Mechanics & Astronomy) 2023年第9期66卷 23-41页

作者： Arshad Ali ya-peng Hu Mudassar Sabir Taotao Sui College of Physics Nanjing University of Aeronautics and AstronauticsNanjing 211106China Key Laboratory of Aerospace Information Materials and Physics(NUAA) MIITNanjing 211106China Center for Gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou 225009China School of Geophysics and Geomatics China University of GeosciencesWuhan 430074China

We revisit the vital issue of gauge dependence in the scalar-induced secondary gravitational waves(SIGWs), focusing on the radiation domination(RD) and matter domination(MD) eras. The energy density spectrum is the main physical observable in such induced gravitational waves. For various gauge choices, there has been a divergence in the energy density, ?GW, of *** calculate SIGWs in diferent gauges to quantify this divergence to address the gauge-dependent problem. In our previous studies, we had found that the energy density diverges in the polynomial power of conformal time(e.g., η^(6) in uniform density gauge). We try to fix this discrepancy by adding a counter-term that removes the fictitious terms in secondary tensor perturbations. We graphically compare the calculations in various gauges and also comment on the physical origin of the observed gauge dependence.

关键词： scalar induced gravitational waves gauge transformation cosmology

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MD simulation of a copper rod under thermal shock

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Acta Mechanica Sinica 2010年第4期26卷 599-604页

作者： Rong-Hou Xia Xiao-Geng Tian ya-peng Shen MOE Key Laboratory for Strength andVibration Xi'an Jiaotong University Xi'an 710049 China Xi'an University of Technology Xi'an 710048 China

In this paper, thermoelastic problem of onedimensional copper rod under thermal shock is simulated using molecular dynamics method by adopting embedded atom method potential. The rod is on axis x, the left outermost surface of which is traction free and the right outermost surface is fixed. Free boundary condition is imposed on the outermost surfaces in direction y and z. The left and right ends of the rod are subjected to hot and cold baths, respectively. Temperature, displacement and stress distributions are obtained along the rod at different moments, which are shown to be limited in the mobile region, indicating that the heat propagation speed is limited rather than infinite. This is consistent with the prediction given by generalized thermoelastic theory. From simulation results we find that the speed of heat conduction is the same as the speed of thermal stress wave. In the present paper, the simulations are conducted using the large-scale atomic/molecular massively parallel simulator and completed visualization software.

关键词： Embedded atom method potential Molecular dynamics simulation Thermoelastic coupling Thermal stress

Surface for methane combustion:O(^3P)+CH4→OH+CH3

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Chinese Physics B 2020年第7期29卷 286-294页

作者： ya peng Zhong-An Jiang Ju-Shi Chen School of Civil and Resource Engineering University of Science and Technology BeijingBeijing 100083China

Kinetic investigations including quasi-classical trajectory and canonical unified statistical theory method calculations are carried out on a potential energy surface for the hydrogen-abstraction reaction from methane by atom O(^3P).The surface is constructed using a modified Shepard interpolation *** ab initio calculations are performed at the CCSD(T)*** account of the contribution of inner core electrons to electronic correlation interaction in ab initio electronic structure calculations,modified optimized aug-cc-pCVQZ basis sets are applied to the all-electrons *** this potential energy surface,the triplet oxygen atom attacks methane in a near-collinear H-CH3 direction to form a saddle point with barrier height of 13.55 kcal/mol,which plays a key role in the kinetics of the title *** the temperature range of 298-2500 K,our calculated thermal rate constants for the O(^3P)+CH4→OH+CH3 reaction show good agreement with relevant experimental *** work provides detailed mechanism of this gas-phase reaction and a theoretical guidance for methane combustion.

关键词： methane combustion potential energy surface transition state kinetic ab initio electronic structure calculation

Symmetry energy of strange quark matter and tidal deformability of strange quark stars

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Nuclear Science and Techniques 2022年第11期33卷 89-100页

作者： Jian-Feng Xu Cheng-Jun Xia Zhen-yan Lu Guang-Xiong peng ya-peng Zhao College of Information Engineering Suqian UniversitySuqian 223800China School of Physics and Electrical Engineering AnYang Normal UniversityAnyang 455000China Center for Gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou 225009China Hunan Provincial Key Laboratory of Intelligent Sensors and Advanced Sensor Materials School of Physics and ElectronicsHunan University of Science and TechnologyXiangtan 411201China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China Institute of High-Energy Physics Chinese Academy of SciencesBeijing 100049China School of Mathematics and Physics Henan Urban Construction UniversityPingdingshan 467036China

Research performed during the past decade revealed an important role of symmetry energy in the equation of state(EOS)of strange quark matter(SQM).By introducing an isospin-dependent term into the quark mass scaling,the SQM stability window in the equivparticle model was *** results show that a sufficiently strong isospin dependence C_(I)can significantly widen the SQM region of absolute stability,yielding results that simultaneously satisfy the constraints of the astrophysical observations of PSR J1614-2230 with 1.928±0.017 Mand tidal deformability 70≤Λ_(1:4)≤580 measured in the event *** increasing C_(I),the difference between the u,d,and s quark fractions for the SQM inβ-equilibrium becomes inconspicuous for C>0,leading to small isospin asymmetryδ,and further resulting in similar EOS and structures of strange quark stars(SQSs).Moreover,unlike the behavior of the maximum mass of ud QSs,which varies with C_(I)depending on the sign of the parameter C,the maximum mass of the SQSs decreases monotonously with increasing CI.

关键词： Symmetry energy Strange quark matter Strange stars Tidal deformability

Tunable fabrication of single-crystalline CsPbI_(3) nanobelts and their application as photodetectors

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International Journal of Minerals,Metallurgy and Materials 2021年第6期28卷 1030-1037页

作者： Tao yang ya-peng Zheng Kuo-Chih Chou Xin-mei Hou Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China

Lead halide perovskites have received increasing attention recently as a candidate material in various optoelectronic areas because of their high performance as light ***,we report the growth of CsPbI_(3) nanobelts via a solution process.A single-crystalline CsPbI_(3) nanobelt with uniform morphology can be achieved by controlling the amount of PbI_(2).A single-crystalline CsPbI_(3) nanobelt possesses a mean width,length,and thickness of 100 nm,5μm,and 20 nm,*** this work,photodetectors(PDs)based on individual CsPbI_(3) nanobelts are constructed and found to perform well with an external quantum efficiency and responsivity of 2.39×10^(5)% and 770 A/W,*** PDs also show a high detectivity of up to 3.12×10^(12) Jones,which is at par with that of Si *** PDs developed in this work exhibit great promise in various optoelectronic nanodevices.

关键词： photodetector cesium lead triiodide perovskite nanobelt detectivity

Identifying influential spreaders in complex networks based on entropy weight method and gravity law

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Chinese Physics B 2020年第4期29卷 582-590页

作者： Xiao-Li yan ya-peng Cui Shun-Jiang Ni Institute of Public Safety Research Tsinghua UniversityBeijing 100084China Department of Engineering Physics Tsinghua UniversityBeijing 100084China Beijing Key Laboratory of City Integrated Emergency Response Science Beijing 100084China

In complex networks,identifying influential spreader is of great significance for improving the reliability of networks and ensuring the safe and effective operation of ***,it is widely used in power networks,aviation networks,computer networks,and social networks,and so *** centrality methods mainly include degree centrality,closeness centrality,betweenness centrality,eigenvector centrality,k-shell,***,single centrality method is onesided and inaccurate,and sometimes many nodes have the same centrality value,namely the same ranking result,which makes it difficult to distinguish between *** to several classical methods of identifying influential nodes,in this paper we propose a novel method that is more full-scaled and universally *** into account in this method are several aspects of node’s properties,including local topological characteristics,central location of nodes,propagation characteristics,and properties of neighbor *** view of the idea of the multi-attribute decision-making,we regard the basic centrality method as node’s attribute and use the entropy weight method to weigh different attributes,and obtain node’s combined ***,the combined centrality is applied to the gravity law to comprehensively identify influential nodes in ***,the classical susceptible-infected-recovered(SIR)model is used to simulate the epidemic spreading in six real-society *** proposed method not only considers the four topological properties of nodes,but also emphasizes the influence of neighbor nodes from the aspect of *** is proved that the new method can effectively overcome the disadvantages of single centrality method and increase the accuracy of identifying influential nodes,which is of great significance for monitoring and controlling the complex networks.

关键词： complex networks influential nodes entropy weight method gravity law

Exploring individuals’ effective preventive measures against epidemics through reinforcement learning

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Chinese Physics B 2021年第4期30卷 640-647页

作者： ya-peng Cui Shun-Jiang Ni Shi-Fei Shen Institute of Public Safety Research Tsinghua UniversityBeijing 100084China Department of Engineering Physics Tsinghua UniversityBeijing 100084China Beijing Key Laboratory of City Integrated Emergency Response Science Beijing 100084China

Individuals’ preventive measures,as an effective way to suppress epidemic transmission and to protect themselves from infection,have attracted much academic concern,especially during the COVID-19 *** this paper,a reinforcement learning-based model is proposed to explore individuals’ effective preventive measures against *** extensive simulations,we find that the cost of preventive measures influences the epidemic transmission process *** infection scale increases as the cost of preventive measures grows,which means that the government needs to provide preventive measures with low cost to suppress the epidemic *** addition,the effective preventive measures vary from individual to individual according to the social *** who contact with others frequently in daily life are highly recommended to take strict preventive measures to protect themselves from infection,while those who have little social contacts do not need to take any measures considering the inevitable *** research contributes to exploring the effective measures for individuals,which can provide the government and individuals useful suggestions in response to epidemics.

关键词： epidemic simulation complex networks reinforcement learning preventive measures

Surface Modification of Polypropylene by Ethylene Plasma and Its Induced β-Form in Polypropylene

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Chinese Journal of Polymer Science 2015年第5期33卷 669-669,670-673页

作者：马桂秋 ya-peng Liu Shu-xian Wei Jing Sheng School of Materials Science and Engineering Tianjin Key Laboratory of Composite and Functional MaterialsTianjin University

This study aims to investigate the chemical structure and morphology of plasmapolymers produced by deposition of ethylene on the surface of polypropylene. The deposition films（sediments） of ethylene plasma on the surface of polypropylene are nonuniform, and the characterization results indicate the existence of hydroxyl groups and aldehyde（or ketone） groups in the sediments. The sediment of ethylene plasma on the polypropylene surface could induce the growth of β-form crystals in the surface layer of polypropylene.

关键词： Plasma polymerization Plasma modification of polypropylene β-Form polypropylene

Effects of Ionic Strength and Sesquioxides on Adsorption of Toxin of Bacillus thuringiensis *** on Soils

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Pedosphere 2012年第1期22卷 96-102页

作者： FU Qing-Ling peng ya-Wen HUANG Tao HU Hong-Qing DENG ya-Li YU Xia Key Laboratory of Subtropical Agricultural Resource and Environment Ministry of AgricultureHuazhong AgriculturalUniversityWuhan 430070(China)

Chemical reactions and fate of the toxins of Bacillus thuringiensis （Bt） in the soil environment are causing increasing concerns due to the large-scale cultivation of transgenic Bt plants. In this study, the effect of ionic strength （0-1 000 mmol kg-1） adjusted by NaCl or CaCl2 on adsorption of Bt toxin by a lateritic red soil, a paddy soil and these soils after chemical removal of organic-bound or free Fe and Al oxides, as well as by pure minerals （goethite, hematite and gibbsite） which are widespread in these soils, were studied. The results indicated that when the supporting electrolyte was NaCl, the adsorption of Bt toxin by the lateritic red soil and paddy soil increased rapidly until the ionic strength reached 250 mmol kg-1 and then gradually slowed down with the increase of ionic strength; while in ease the supporting electrolyte was CaCl2, the adsorption of Bt toxin enhanced significantly at low ionic strength （〈 10 mmol kg-1） and then decreased as the ionic strength increased. The adsorption of Bt toxin by the tested minerals and soils after the removal of organic-bound or free Fe and Al oxides also increased with increasing ionic strength controlled by NaCl. Removing organic-bound Fe and Al oxides obviously increased the adsorption of Bt toxin in the tested soils. Differently, removing free Fe and Al oxides increased the Bt adsorption by the paddy soil, but decreased the adsorption by the lateritic red soil. The study indicated that the varieties of ionic strength and the presence of Ve and Al oxides affected the adsorption of Bt toxin by the soils, which would contribute to the further understanding of the fate of Bt toxin in the soil environment and provide references for the ecological risk assessment of transgenic Bt plants.

关键词： Al oxides Fe oxides lateritic red soil paddy soil supporting electrolyte