In a recent paper(Luo H et al.,2022),we found that the peak amplitudes of diurnal magnetic variations,measured during martian days(sols)at the InSight landing site,exhibited quasi Carrington-Rotation(qCR)periods at hi...In a recent paper(Luo H et al.,2022),we found that the peak amplitudes of diurnal magnetic variations,measured during martian days(sols)at the InSight landing site,exhibited quasi Carrington-Rotation(qCR)periods at higher eigenmodes of the natural orthogonal components(NOC);these results were based on~664 sols of magnetic field measurements.However,the source of these periodic variations is still unknown.In this paper we introduce the neutral-wind driven ionospheric dynamo current model(e.g.,Lillis et al.,2019)to investigate the source.Four candidates-the draped IMF,electron density/plasma density,the neutral densities,and the electron temperature in the ionosphere with artificial qCR periodicity,are applied in the modeling to find the main factor likely to be causing the observed surface magnetic field variations that exhibit the same qCR periods.Results show that the electron density/plasma density,which controls the total conductivity in the dynamo region,appears to account for the greatest part of the surface qCR variations;its contribution reaches about 67.6%.The draped IMF,the neutral densities,and the electron temperature account,respectively,for only about 12.9%,10.3%,and 9.2%of the variations.Our study implies that the qCR magnetic variations on the Martian surface are due primarily to variations of the dynamo currents caused by the electron density variations.We suggest also that the timevarying fields with the qCR period could be used to probe the Martian interior's electrical conductivity structure to a depth of at least 700 km.展开更多
Exact analytical solution for flows of an electrically conducting fluid over an infinite oscillatory disk in the presence of a uniform transverse magnetic field is constructed. Both the disk and the fluid are in a sta...Exact analytical solution for flows of an electrically conducting fluid over an infinite oscillatory disk in the presence of a uniform transverse magnetic field is constructed. Both the disk and the fluid are in a state of non-coaxial rotation. Such a flow model has a great significance not only due to its own theoretical interest, but also due to applications to geophysics and engineering. The resulting initial value problem has been solved analytically by applying the Laplace transform technique and the explicit expressions for the velocity for steady and unsteady cases have been established. The analysis of the obtained results shows that the flow field is appreciably influenced by the applied magnetic field, the frequency and rotation parameters.展开更多
In this study, the iterative harmonic balance method was used to develop analytical solutions of period-one rotations of a pendulum driven horizontally by harmonic excitations. The performance of the method was evalua...In this study, the iterative harmonic balance method was used to develop analytical solutions of period-one rotations of a pendulum driven horizontally by harmonic excitations. The performance of the method was evaluated by two criteria, one based on the system energy error and the other based on the global residual error. As a comparison, analytical solutions based on the multi-scale method were also considered. Numerical solutions obtained from the Dormand-Prince method (ODE45 in MATLAB©) were used as the baseline for evaluation. It was found that under lower-level excitations, the multi-scale method performed better than the iterative method. At higher-level excitations, however, the performance of the iterative method was noticeably more accurate.展开更多
We analyse the appearance of coherent motion in the dynamics of the Langevin equation in the subtle case of I<1,and show that stochastic resonance does exist even in the non-critical case I<1.Moreover,we show th...We analyse the appearance of coherent motion in the dynamics of the Langevin equation in the subtle case of I<1,and show that stochastic resonance does exist even in the non-critical case I<1.Moreover,we show the monotonicity of the rotation number and discuss the relationship between the center frequency of the power spectrum peak and the rotation number.展开更多
Combined effects of centrifugal and coriolis instability of the flow through a rotating curved duct with rectangular cross section have been studied numerically by using a spectral method, and covering a wide range of...Combined effects of centrifugal and coriolis instability of the flow through a rotating curved duct with rectangular cross section have been studied numerically by using a spectral method, and covering a wide range of the Taylor number ?for a constant Dean number. The rotation of the duct about the center of curvature is imposed in the positive direction, and the effects of rotation (Coriolis force) on the flow characteristics are investigated. As a result, multiple branches of asymmetric steady solutions with two-, three-and multi-vortex solutions are obtained. To investigate the non-linear behavior of the unsteady solutions, time evolution calculations as well as power spectrum of the unsteady solutions are performed, and it is found that the unsteady flow undergoes through various flow instabilities in the scenario “chaotic?→ multi-periodic?→ periodic?→ steady-state”, if Tr is increased in the positive direction. The present results show the characteristics of both the secondary flow and axial flow distribution in the flow.展开更多
Building on the idea that molecules in liquid phase associate into multi-molecular complexes through covalent bonds, the present article focuses on the possible structures of these complexes. Saturation at atomic leve...Building on the idea that molecules in liquid phase associate into multi-molecular complexes through covalent bonds, the present article focuses on the possible structures of these complexes. Saturation at atomic level is a key concept to understand where connections occur and how far molecules aggregate. A periodic table for liquids with saturation levels is proposed, in agreement with the even-odd rule, for both organic and inorganic elements. With the aim at reaching the most stable complexes, meaning no other chemical reactions can occur in the liquid phase, the structure of complexes resulting from liquefaction of about 30 molecules is devised. The article concludes that complexes in liquids generally assume rounded shapes of an intermediate size between gas and solid structures. It shows that saturation and covalent bonds alone can explain the specific properties of liquids. While it is generally acknowledged that molecular energy in gases and solids are respectively linear kinetic and vibratory, we suggest that rotatory energy dominates in liquids.展开更多
为研究地球自转速率变化的非线性特性,结合自适应噪声完备经验模态分解、定量递归分析和Grassberger-Procaccia算法,从周期、混沌和分形多角度对1962年1月1日至2023年12月31日反映地球自转速率变化的日长变化(length of day,ΔLOD)观测...为研究地球自转速率变化的非线性特性,结合自适应噪声完备经验模态分解、定量递归分析和Grassberger-Procaccia算法,从周期、混沌和分形多角度对1962年1月1日至2023年12月31日反映地球自转速率变化的日长变化(length of day,ΔLOD)观测序列的非线性特性进行全面分析,并着重对比分析扣除周期成分或混沌成分前后ΔLOD特性是否存在明显区别.主要结论如下:1)ΔLOD时间序列由趋势成分、周期成分和混沌成分构成,具有明显的多时间尺度、混沌动力学特性和分形结构;2)扣除混沌成分后的时间序列周期与原始ΔLOD时间序列的周期完全相同;3)原始ΔLOD时间序列和其扣除趋势成分和周期成分后的时间序列的混沌特性无显著性差异,但前者分形结构的复杂性相对更强.展开更多
Ⅰ. INTRODUCTION The rate of periodical change, (?), is one of the most important parameters for pulsars, for it provides a lot of valuable information for studying the physical processes of them. At present, the intr...Ⅰ. INTRODUCTION The rate of periodical change, (?), is one of the most important parameters for pulsars, for it provides a lot of valuable information for studying the physical processes of them. At present, the intrinsic mechanisms of pulsar radiation展开更多
A novel design of optical sampling system has been developed by using sum-frequency generation （SFG） in a periodically-poled lithium niobate （PPLN） waveguide and using passive mode-locked fiber laser pulses as opt...A novel design of optical sampling system has been developed by using sum-frequency generation （SFG） in a periodically-poled lithium niobate （PPLN） waveguide and using passive mode-locked fiber laser pulses as optical sampling pulses. The system achieved high temporal resolution and high sensitivity using a 30 mm length PPLN with quasi phase match period of 19.3 μm and 151 fs sampling pulses which were generated by passive modelock fiber laser based on nonlinear polarization rotation （NPR）. Clear eye-diagram of 10 Gbit/s non-return-to-zeros （NRZ） pseudorandom binary sequence （PRBS） optical signal were successfully reconstructed by this system.展开更多
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB41010304)the National Key R&D Program of China (Grant No.2018YFC1503806)the National Natural Science Foundation of China (41874080, 41674168, 41874197)
文摘In a recent paper(Luo H et al.,2022),we found that the peak amplitudes of diurnal magnetic variations,measured during martian days(sols)at the InSight landing site,exhibited quasi Carrington-Rotation(qCR)periods at higher eigenmodes of the natural orthogonal components(NOC);these results were based on~664 sols of magnetic field measurements.However,the source of these periodic variations is still unknown.In this paper we introduce the neutral-wind driven ionospheric dynamo current model(e.g.,Lillis et al.,2019)to investigate the source.Four candidates-the draped IMF,electron density/plasma density,the neutral densities,and the electron temperature in the ionosphere with artificial qCR periodicity,are applied in the modeling to find the main factor likely to be causing the observed surface magnetic field variations that exhibit the same qCR periods.Results show that the electron density/plasma density,which controls the total conductivity in the dynamo region,appears to account for the greatest part of the surface qCR variations;its contribution reaches about 67.6%.The draped IMF,the neutral densities,and the electron temperature account,respectively,for only about 12.9%,10.3%,and 9.2%of the variations.Our study implies that the qCR magnetic variations on the Martian surface are due primarily to variations of the dynamo currents caused by the electron density variations.We suggest also that the timevarying fields with the qCR period could be used to probe the Martian interior's electrical conductivity structure to a depth of at least 700 km.
文摘Exact analytical solution for flows of an electrically conducting fluid over an infinite oscillatory disk in the presence of a uniform transverse magnetic field is constructed. Both the disk and the fluid are in a state of non-coaxial rotation. Such a flow model has a great significance not only due to its own theoretical interest, but also due to applications to geophysics and engineering. The resulting initial value problem has been solved analytically by applying the Laplace transform technique and the explicit expressions for the velocity for steady and unsteady cases have been established. The analysis of the obtained results shows that the flow field is appreciably influenced by the applied magnetic field, the frequency and rotation parameters.
文摘In this study, the iterative harmonic balance method was used to develop analytical solutions of period-one rotations of a pendulum driven horizontally by harmonic excitations. The performance of the method was evaluated by two criteria, one based on the system energy error and the other based on the global residual error. As a comparison, analytical solutions based on the multi-scale method were also considered. Numerical solutions obtained from the Dormand-Prince method (ODE45 in MATLAB©) were used as the baseline for evaluation. It was found that under lower-level excitations, the multi-scale method performed better than the iterative method. At higher-level excitations, however, the performance of the iterative method was noticeably more accurate.
文摘We analyse the appearance of coherent motion in the dynamics of the Langevin equation in the subtle case of I<1,and show that stochastic resonance does exist even in the non-critical case I<1.Moreover,we show the monotonicity of the rotation number and discuss the relationship between the center frequency of the power spectrum peak and the rotation number.
文摘Combined effects of centrifugal and coriolis instability of the flow through a rotating curved duct with rectangular cross section have been studied numerically by using a spectral method, and covering a wide range of the Taylor number ?for a constant Dean number. The rotation of the duct about the center of curvature is imposed in the positive direction, and the effects of rotation (Coriolis force) on the flow characteristics are investigated. As a result, multiple branches of asymmetric steady solutions with two-, three-and multi-vortex solutions are obtained. To investigate the non-linear behavior of the unsteady solutions, time evolution calculations as well as power spectrum of the unsteady solutions are performed, and it is found that the unsteady flow undergoes through various flow instabilities in the scenario “chaotic?→ multi-periodic?→ periodic?→ steady-state”, if Tr is increased in the positive direction. The present results show the characteristics of both the secondary flow and axial flow distribution in the flow.
文摘Building on the idea that molecules in liquid phase associate into multi-molecular complexes through covalent bonds, the present article focuses on the possible structures of these complexes. Saturation at atomic level is a key concept to understand where connections occur and how far molecules aggregate. A periodic table for liquids with saturation levels is proposed, in agreement with the even-odd rule, for both organic and inorganic elements. With the aim at reaching the most stable complexes, meaning no other chemical reactions can occur in the liquid phase, the structure of complexes resulting from liquefaction of about 30 molecules is devised. The article concludes that complexes in liquids generally assume rounded shapes of an intermediate size between gas and solid structures. It shows that saturation and covalent bonds alone can explain the specific properties of liquids. While it is generally acknowledged that molecular energy in gases and solids are respectively linear kinetic and vibratory, we suggest that rotatory energy dominates in liquids.
文摘为研究地球自转速率变化的非线性特性,结合自适应噪声完备经验模态分解、定量递归分析和Grassberger-Procaccia算法,从周期、混沌和分形多角度对1962年1月1日至2023年12月31日反映地球自转速率变化的日长变化(length of day,ΔLOD)观测序列的非线性特性进行全面分析,并着重对比分析扣除周期成分或混沌成分前后ΔLOD特性是否存在明显区别.主要结论如下:1)ΔLOD时间序列由趋势成分、周期成分和混沌成分构成,具有明显的多时间尺度、混沌动力学特性和分形结构;2)扣除混沌成分后的时间序列周期与原始ΔLOD时间序列的周期完全相同;3)原始ΔLOD时间序列和其扣除趋势成分和周期成分后的时间序列的混沌特性无显著性差异,但前者分形结构的复杂性相对更强.
文摘Ⅰ. INTRODUCTION The rate of periodical change, (?), is one of the most important parameters for pulsars, for it provides a lot of valuable information for studying the physical processes of them. At present, the intrinsic mechanisms of pulsar radiation
基金The project was supported by Open Fund of State Key Laboratory of Information Photonics and Optical Communications （Beijing University of Posts and Telecommunications）, the National Natural Science Foundation of China （Grant Nos. 60978007, 61027007 and 61177067）
文摘A novel design of optical sampling system has been developed by using sum-frequency generation （SFG） in a periodically-poled lithium niobate （PPLN） waveguide and using passive mode-locked fiber laser pulses as optical sampling pulses. The system achieved high temporal resolution and high sensitivity using a 30 mm length PPLN with quasi phase match period of 19.3 μm and 151 fs sampling pulses which were generated by passive modelock fiber laser based on nonlinear polarization rotation （NPR）. Clear eye-diagram of 10 Gbit/s non-return-to-zeros （NRZ） pseudorandom binary sequence （PRBS） optical signal were successfully reconstructed by this system.
