Taking note of China-U.S.bilateral relations in recent years,we could conclude that relations between the two most powerful nations in the world have reached disturbing new lows and that might lead to much worse yet t...Taking note of China-U.S.bilateral relations in recent years,we could conclude that relations between the two most powerful nations in the world have reached disturbing new lows and that might lead to much worse yet to come.U.S.Secretary of State Antony Blinken had described ties between Beijing and Washington,D.C.as“unstable”before embarking on his two-day trip to China's capital on June 18-19.展开更多
We investigate the temperature dependence of the emission spectrum of a laser-induced semiconductor（Ge and Si） plasma. The change in spectral intensity with the sample temperature indicates the change of the laser a...We investigate the temperature dependence of the emission spectrum of a laser-induced semiconductor（Ge and Si） plasma. The change in spectral intensity with the sample temperature indicates the change of the laser ablation mass. The reflectivity of the target surface is reduced as the sample is heated, which leads to an increase in the laser energy coupled to the surface of the sample and eventually produces a higher spectral intensity.The spectral intensities are enhanced by a few times at high temperatures compared with the cases at low temperatures. The spectral intensity of Ge is enhanced by 1.5 times at 422.66 nm, and 3 times at589.33 nm when the sample temperature increases from 50°C to 300°C. We can obtain the same emission intensity by a more powerful laser or by less pulse energy with a higher sample temperature. Based on experimental observations we conclude that the preheated sample can improve the emission intensity of laser-induced semiconductor plasma spectroscopy.展开更多
Sudden mega natural gas leaks of two Nord Stream pipelines in the Baltic Sea(Denmark)occurred from late September to early October 2022,releasing large amounts of methane into the atmosphere.We inferred the methane em...Sudden mega natural gas leaks of two Nord Stream pipelines in the Baltic Sea(Denmark)occurred from late September to early October 2022,releasing large amounts of methane into the atmosphere.We inferred the methane emissions of this event based on surface in situ observations using two inversion methods and two meteorological reanalysis datasets,supplemented with satellite-based observations.We conclude that approximately 220±30 Gg of methane was released from September 26 to October 1,2022.展开更多
The bulk properties of materials in an extreme environment such as high temperature and high pressure can be understood by studying anharmonic effects due to the vibration of lattice ions and thermally excited electro...The bulk properties of materials in an extreme environment such as high temperature and high pressure can be understood by studying anharmonic effects due to the vibration of lattice ions and thermally excited electrons.In this spirit,in the present paper,anharmonic effects are studied by using the recently proposed mean-field potential（MFP） approach and Mermin functional which arise due to the vibration of lattice ions and thermally excited electrons,respectively.The MFP experienced by a wanderer atom in the presence of surrounding atoms is constructed in terms of cold energy using the local form of the pseudopotential.We have calculated the temperature variation of several thermophysical properties in an extreme environment up to melting temperature.The results of our calculations are in excellent agreement with the experimental findings as well as the theoretical results obtained by using first principle methods.We conclude that presently used conjunction scheme（MFP＋pseudo potential） is simple computationally,transparent physically,and accurate in the sense that the results generated are comparable and sometimes better than the results obtained by first principle methods.Local pseudopotential used is transferable to extreme environment without adjusting its parameters.展开更多
In this paper we study the existence of limit cycle for cubic system (E)_3, of Kolmogorov typewith a conic algebraic trajectoryF_2(x,y)=ax^2+2bxy+cy^2+dx+ey+f=0 It has been proved in my former papers that (E)_3 doesn&...In this paper we study the existence of limit cycle for cubic system (E)_3, of Kolmogorov typewith a conic algebraic trajectoryF_2(x,y)=ax^2+2bxy+cy^2+dx+ey+f=0 It has been proved in my former papers that (E)_3 doesn't have any limit cycle on the whole planeIf b^2-ac≠0, Now we are investigating the case where b^2-ac=0. We prove the sufficient andnecessary formula (2) or (13) witb which (E)_3 must have a parabolic trajectory F_2(x,y)=0. Thenthere will not be any limit cycle on the full plane. On the basis of this, we conclude: The cubic system of Kolmogorov type with a non-degenerated quadratic algebraic trajectory onthe whole plane has no limit cycle.展开更多
文摘Taking note of China-U.S.bilateral relations in recent years,we could conclude that relations between the two most powerful nations in the world have reached disturbing new lows and that might lead to much worse yet to come.U.S.Secretary of State Antony Blinken had described ties between Beijing and Washington,D.C.as“unstable”before embarking on his two-day trip to China's capital on June 18-19.
基金supported by the National Natura Science Foundation of China(Nos.11674128,11474129and 11504129)the National 973 Program of China(No.2013CB922200)the China Postdoctoral Science Foundation(No.2014M551169)
文摘We investigate the temperature dependence of the emission spectrum of a laser-induced semiconductor（Ge and Si） plasma. The change in spectral intensity with the sample temperature indicates the change of the laser ablation mass. The reflectivity of the target surface is reduced as the sample is heated, which leads to an increase in the laser energy coupled to the surface of the sample and eventually produces a higher spectral intensity.The spectral intensities are enhanced by a few times at high temperatures compared with the cases at low temperatures. The spectral intensity of Ge is enhanced by 1.5 times at 422.66 nm, and 3 times at589.33 nm when the sample temperature increases from 50°C to 300°C. We can obtain the same emission intensity by a more powerful laser or by less pulse energy with a higher sample temperature. Based on experimental observations we conclude that the preheated sample can improve the emission intensity of laser-induced semiconductor plasma spectroscopy.
基金supported by the National Key R&D Program of China(Grant No:2021YFB3901001)Research Funds for the Frontiers Science Center for Critical Earth Material Cycling,Nanjing University(Grant No:090414380031)National Natural Science Foundation of China(Grant No:42007198)。
文摘Sudden mega natural gas leaks of two Nord Stream pipelines in the Baltic Sea(Denmark)occurred from late September to early October 2022,releasing large amounts of methane into the atmosphere.We inferred the methane emissions of this event based on surface in situ observations using two inversion methods and two meteorological reanalysis datasets,supplemented with satellite-based observations.We conclude that approximately 220±30 Gg of methane was released from September 26 to October 1,2022.
基金Project supported by the Department of Science and Technology-Fund for Improvement of Science and Technology Infrastructure Project(DST-FIST)(Level 1)of Department of Sciences and Technology(DST),New Delhi(Grant No.SR/FST/PST-001/2006)
文摘The bulk properties of materials in an extreme environment such as high temperature and high pressure can be understood by studying anharmonic effects due to the vibration of lattice ions and thermally excited electrons.In this spirit,in the present paper,anharmonic effects are studied by using the recently proposed mean-field potential（MFP） approach and Mermin functional which arise due to the vibration of lattice ions and thermally excited electrons,respectively.The MFP experienced by a wanderer atom in the presence of surrounding atoms is constructed in terms of cold energy using the local form of the pseudopotential.We have calculated the temperature variation of several thermophysical properties in an extreme environment up to melting temperature.The results of our calculations are in excellent agreement with the experimental findings as well as the theoretical results obtained by using first principle methods.We conclude that presently used conjunction scheme（MFP＋pseudo potential） is simple computationally,transparent physically,and accurate in the sense that the results generated are comparable and sometimes better than the results obtained by first principle methods.Local pseudopotential used is transferable to extreme environment without adjusting its parameters.
文摘In this paper we study the existence of limit cycle for cubic system (E)_3, of Kolmogorov typewith a conic algebraic trajectoryF_2(x,y)=ax^2+2bxy+cy^2+dx+ey+f=0 It has been proved in my former papers that (E)_3 doesn't have any limit cycle on the whole planeIf b^2-ac≠0, Now we are investigating the case where b^2-ac=0. We prove the sufficient andnecessary formula (2) or (13) witb which (E)_3 must have a parabolic trajectory F_2(x,y)=0. Thenthere will not be any limit cycle on the full plane. On the basis of this, we conclude: The cubic system of Kolmogorov type with a non-degenerated quadratic algebraic trajectory onthe whole plane has no limit cycle.
