Using the density functional B3P86/cc-PV5Z method, the geometric structure of BH molecule under different external electric fields is optimized, and the bond lengths, dipole moments, vibration frequencies, and other p...Using the density functional B3P86/cc-PV5Z method, the geometric structure of BH molecule under different external electric fields is optimized, and the bond lengths, dipole moments, vibration frequencies, and other physical properties parameters are obtained. On the basis of setting appropriate parameters, scanning single point energies are obtained by the same method and the potential energy curves under different external fields are also obtained. These results show that the physical property parameters and potential energy curves may change with external electric field, especially in the case of reverse direction electric field. The potential energy function without external electric field is fitted by Morse potential, and the fitting parameters are obtained which are in good agreement with experimental values. In order to obtain the critical dissociation electric parameter, the dipole approximation is adopted to construct a potential model fitting the corresponding potential energy curve of the external electric field. It is found that the fitted critical dissociation electric parameter is consistent with numerical calculation, so that the constructed model is reliable and accurate. These results will provide important theoretical and experimental reference for further studying the molecular spectrum, dynamics, and molecular cooling with Stark effect.展开更多
The deconfinement phase transition with external magnetic field is investigated in the Friedberg-Lee model. We expand the potentiM around the two locM minima of the first-order deconfinement phase transition and extra...The deconfinement phase transition with external magnetic field is investigated in the Friedberg-Lee model. We expand the potentiM around the two locM minima of the first-order deconfinement phase transition and extract the ground state of the system in the frame of functional renormalization group. By solving the flow equations we find that the magnetic field displays a catalysis effect and it becomes more difficult to break through the confinement.展开更多
Based on observations and historical simulations from the fifth phase of the Coupled Model Intercomparison Project(CMIP5) archive, the contributions of human activities(including greenhouse gases(GHGs), anthropogenic ...Based on observations and historical simulations from the fifth phase of the Coupled Model Intercomparison Project(CMIP5) archive, the contributions of human activities(including greenhouse gases(GHGs), anthropogenic aerosols(AAs), and land use(LU)) and external natural forcings(Nat) to climate changes in China over the past 50 years were quantified. Both anthropogenic and external natural forcings account for 95%–99% of the observed temperature change from 1951–1975 to 1981–2005. In particular, the temperature changes induced by GHGs are approximately 2–3 times stronger than the observed changes, and AAs impose a significant cooling effect. The total external forcings can explain 65%–78% of the observed precipitation changes over the past 50 years, in which AAs and GHGs are the primary external forcings leading to the precipitation changes; in particular, AAs dominate the main spatial features of precipitation changes in eastern China. Human activities also dominate the long-term non-linear trends in observed temperature during the past several decades, and, in particular, GHGs, the primary warming contributor, have produced significant warming since the 1960 s. Compared to the long-term non-linear trends in observed precipitation, GHGs have largely caused the wetting changes in the arid-semiarid region since the 1970 s, whereas AAs have led to the drying changes in the humid-semihumid region; both LU and Nat can impose certain impacts on the long-term non-linear trends in precipitation. Using the optimal fingerprinting detection approach, the effects of human activities on the temperature changes can be detected and attributed in China, and the effect of GHGs can be clearly detected from the observations in humid-semihumid areas. However, the anthropogenic effects cannot be detected in the observed precipitation changes, which may be due to the uncertainties in the model simulations and to other issues. Although some results in this paper still need improvement due to uncertainties in the coupled models, this study is expected to provide the background and scientific basis for climate changes to conduct vulnerability and risk assessments of the ecological systems and water resources in the arid-semiarid region of China.展开更多
In contrast to Ref.[1]studying MHD processes in a helical channel induced by a vertical rotating electric current layer,in the present report we examine another version with the rotating electric current layer orthogo...In contrast to Ref.[1]studying MHD processes in a helical channel induced by a vertical rotating electric current layer,in the present report we examine another version with the rotating electric current layer orthogonal to the helical channel axis,which leads to an increase in melt velocity with the growing pitch angle α of the helical channel.展开更多
We examine MHD processes arising in melts placed in vessels of circular and rectangular cross-sections under the action of amplitude-and-frequency modulated rotating magnetic field.It is established that besides the m...We examine MHD processes arising in melts placed in vessels of circular and rectangular cross-sections under the action of amplitude-and-frequency modulated rotating magnetic field.It is established that besides the mean turbulent flow,seven oscillations arise in the melt,whose frequency and amplitude depend on modulation parameters.展开更多
We examine a convective dissipation-free heat transfer in melts under the action of a stationary component of electromagnetic body force induced by frequency-modulated travelling magnetic field.The influence of MHD pa...We examine a convective dissipation-free heat transfer in melts under the action of a stationary component of electromagnetic body force induced by frequency-modulated travelling magnetic field.The influence of MHD parameters of turbulent flow on the transfer process is studied.展开更多
In recent years,physics-informed neural networks(PINNs)have shown remarkable potential in modeling conservative systems of rigid-body dynamics.However,when applied to practical interaction tasks of manipulators(e.g.,p...In recent years,physics-informed neural networks(PINNs)have shown remarkable potential in modeling conservative systems of rigid-body dynamics.However,when applied to practical interaction tasks of manipulators(e.g.,part assembly and medical operations),existing PINN frameworks lack effective external force modeling mechanisms,resulting in significantly degraded prediction accuracy in dynamic interaction scenarios.Additionally,because industrial robots(including UR5 and UR10e robots)are generally not equipped with joint torque sensors,obtaining precise dynamics training data remains challenging.To address these issues,this study proposes two enhanced PINNs that integrate motor dynamics and external force modeling.First,two data-driven Jacobian matrix estimation methods are introduced to incorporate external forces:one learns the mapping between endeffector velocity and joint velocity to approximate the Jacobian matrix,while the other first learns the system’s kinematic behavior and then derives the Jacobian matrix through analytical differentiation of the forward kinematics model.Second,current-to-torque mapping is embedded as physical prior knowledge to establish direct correlations between system motion states and motor currents.Experimental results on two different manipulators demonstrate that both models achieve high-precision torque estimation in complex external force scenarios without requiring joint torque sensors.Compared with state-of-the-art methods,the proposed models improve overall modeling accuracy by 31.12%and 37.07%on average across various complex scenarios,while reducing joint trajectory tracking errors by 40.31%and 51.79%,respectively.展开更多
Local hydrodynamics in the riser of an external loop airlift reactor （EL-ALR） are identified and the performances of three drag models are evaluated in computational fluid dynamics simulation. The simulation results...Local hydrodynamics in the riser of an external loop airlift reactor （EL-ALR） are identified and the performances of three drag models are evaluated in computational fluid dynamics simulation. The simulation results show that the Schiller-Naumann drag model underestimated the local gas holdup at lower superficial gas velocity whereas the Tomiyama drag model overestimated that at higher superficial gas velocity. By contrast, the dual-bubble-size （DBS）-local drag model gave more reasonable radial and axial distri-butions of gas holdup in all cases. The reason is that the DBS-local drag model gave correct values of the lumped parameter, i,e., the ratio of the drag coefficient to bubble diameter, for varying operating conditions and radial positions. This ratio is reasonably expected to decrease with increasing superficial gas velocity and be smaller in the center and larger near the wall. Only the DBS-local drag model correctly reproduced these trends. The radial profiles of the axial velocity of the liquid and gas predicted by the DBS-local model also agreed well with experimental data.展开更多
基金Project supported by the National Natural Science Foundation of China(Grand Nos.11147158 and 11264020)the Natural Science Foundation of Jiangxi Province,China(Grand No.2010GQW0031)the Scientific Research Program of the Education Bureau of Jiangxi Province,China(Grand No.GJJ12483)
文摘Using the density functional B3P86/cc-PV5Z method, the geometric structure of BH molecule under different external electric fields is optimized, and the bond lengths, dipole moments, vibration frequencies, and other physical properties parameters are obtained. On the basis of setting appropriate parameters, scanning single point energies are obtained by the same method and the potential energy curves under different external fields are also obtained. These results show that the physical property parameters and potential energy curves may change with external electric field, especially in the case of reverse direction electric field. The potential energy function without external electric field is fitted by Morse potential, and the fitting parameters are obtained which are in good agreement with experimental values. In order to obtain the critical dissociation electric parameter, the dipole approximation is adopted to construct a potential model fitting the corresponding potential energy curve of the external electric field. It is found that the fitted critical dissociation electric parameter is consistent with numerical calculation, so that the constructed model is reliable and accurate. These results will provide important theoretical and experimental reference for further studying the molecular spectrum, dynamics, and molecular cooling with Stark effect.
基金Supported by the National Natural Science Foundation of China under Grant No 11405122the China Postdoctoral Science Foundation under Grant No 2014M550483
文摘The deconfinement phase transition with external magnetic field is investigated in the Friedberg-Lee model. We expand the potentiM around the two locM minima of the first-order deconfinement phase transition and extract the ground state of the system in the frame of functional renormalization group. By solving the flow equations we find that the magnetic field displays a catalysis effect and it becomes more difficult to break through the confinement.
基金National Basic Research Program of China (Grant No. 2012CB956203)the China Meteorological Administration R&D Special Fund for Public Welfare (Meteorology) (Grant No. GYHY201306027)+1 种基金the Open Research Fund Program of Plateau Atmosphere and Environment Key Laboratory of Sichuan Province (Grant No. PAEKL-2015-C1)the National Science Foundation of China (Grant No. 41405090)
文摘Based on observations and historical simulations from the fifth phase of the Coupled Model Intercomparison Project(CMIP5) archive, the contributions of human activities(including greenhouse gases(GHGs), anthropogenic aerosols(AAs), and land use(LU)) and external natural forcings(Nat) to climate changes in China over the past 50 years were quantified. Both anthropogenic and external natural forcings account for 95%–99% of the observed temperature change from 1951–1975 to 1981–2005. In particular, the temperature changes induced by GHGs are approximately 2–3 times stronger than the observed changes, and AAs impose a significant cooling effect. The total external forcings can explain 65%–78% of the observed precipitation changes over the past 50 years, in which AAs and GHGs are the primary external forcings leading to the precipitation changes; in particular, AAs dominate the main spatial features of precipitation changes in eastern China. Human activities also dominate the long-term non-linear trends in observed temperature during the past several decades, and, in particular, GHGs, the primary warming contributor, have produced significant warming since the 1960 s. Compared to the long-term non-linear trends in observed precipitation, GHGs have largely caused the wetting changes in the arid-semiarid region since the 1970 s, whereas AAs have led to the drying changes in the humid-semihumid region; both LU and Nat can impose certain impacts on the long-term non-linear trends in precipitation. Using the optimal fingerprinting detection approach, the effects of human activities on the temperature changes can be detected and attributed in China, and the effect of GHGs can be clearly detected from the observations in humid-semihumid areas. However, the anthropogenic effects cannot be detected in the observed precipitation changes, which may be due to the uncertainties in the model simulations and to other issues. Although some results in this paper still need improvement due to uncertainties in the coupled models, this study is expected to provide the background and scientific basis for climate changes to conduct vulnerability and risk assessments of the ecological systems and water resources in the arid-semiarid region of China.
基金Item Sponsored by framework of International Scientific Project No.C26/251 "MHD Liquid Metal Stirring and its Effect on the Structure of Solidifying Alloys"and Resaerch Center"Mathematical Models of the Continuous Media" (PermRussian Federation)
文摘In contrast to Ref.[1]studying MHD processes in a helical channel induced by a vertical rotating electric current layer,in the present report we examine another version with the rotating electric current layer orthogonal to the helical channel axis,which leads to an increase in melt velocity with the growing pitch angle α of the helical channel.
文摘We examine MHD processes arising in melts placed in vessels of circular and rectangular cross-sections under the action of amplitude-and-frequency modulated rotating magnetic field.It is established that besides the mean turbulent flow,seven oscillations arise in the melt,whose frequency and amplitude depend on modulation parameters.
文摘We examine a convective dissipation-free heat transfer in melts under the action of a stationary component of electromagnetic body force induced by frequency-modulated travelling magnetic field.The influence of MHD parameters of turbulent flow on the transfer process is studied.
基金Project supported by the Beijing Municipal Natural Science Foundation-Xiaomi Innovation Joint Fund(No.L233006)the National Natural Science Foundation of China(Nos.62276028and 92267110)+1 种基金the Qin Xin Talents Cultivation Program at Beijing Information Science and Technology University(No.QXTCP A202102)the Beijing Information Science and Technology University School Research Fund(No.2023XJJ12)。
文摘In recent years,physics-informed neural networks(PINNs)have shown remarkable potential in modeling conservative systems of rigid-body dynamics.However,when applied to practical interaction tasks of manipulators(e.g.,part assembly and medical operations),existing PINN frameworks lack effective external force modeling mechanisms,resulting in significantly degraded prediction accuracy in dynamic interaction scenarios.Additionally,because industrial robots(including UR5 and UR10e robots)are generally not equipped with joint torque sensors,obtaining precise dynamics training data remains challenging.To address these issues,this study proposes two enhanced PINNs that integrate motor dynamics and external force modeling.First,two data-driven Jacobian matrix estimation methods are introduced to incorporate external forces:one learns the mapping between endeffector velocity and joint velocity to approximate the Jacobian matrix,while the other first learns the system’s kinematic behavior and then derives the Jacobian matrix through analytical differentiation of the forward kinematics model.Second,current-to-torque mapping is embedded as physical prior knowledge to establish direct correlations between system motion states and motor currents.Experimental results on two different manipulators demonstrate that both models achieve high-precision torque estimation in complex external force scenarios without requiring joint torque sensors.Compared with state-of-the-art methods,the proposed models improve overall modeling accuracy by 31.12%and 37.07%on average across various complex scenarios,while reducing joint trajectory tracking errors by 40.31%and 51.79%,respectively.
文摘Local hydrodynamics in the riser of an external loop airlift reactor （EL-ALR） are identified and the performances of three drag models are evaluated in computational fluid dynamics simulation. The simulation results show that the Schiller-Naumann drag model underestimated the local gas holdup at lower superficial gas velocity whereas the Tomiyama drag model overestimated that at higher superficial gas velocity. By contrast, the dual-bubble-size （DBS）-local drag model gave more reasonable radial and axial distri-butions of gas holdup in all cases. The reason is that the DBS-local drag model gave correct values of the lumped parameter, i,e., the ratio of the drag coefficient to bubble diameter, for varying operating conditions and radial positions. This ratio is reasonably expected to decrease with increasing superficial gas velocity and be smaller in the center and larger near the wall. Only the DBS-local drag model correctly reproduced these trends. The radial profiles of the axial velocity of the liquid and gas predicted by the DBS-local model also agreed well with experimental data.
