The effects of forced flows at different velocities on microstructure and solute distribution during the directional solidification of Sn-10 wt% Bi alloys under a simultaneous imposition of a transverse static magneti...The effects of forced flows at different velocities on microstructure and solute distribution during the directional solidification of Sn-10 wt% Bi alloys under a simultaneous imposition of a transverse static magnetic field(TSMF) and an external direct current(DC) have been investigated experimentally and numerically. The experimental results show that the solid-liquid interface will gradually become sloping with the increase of the forced flow velocity when the thermoelectric magnetic convection(TEMC)dominates the forced flow at solidification front. However, the interface will gradually become planar as the flow velocity further increases when the electromagnetic convection(EMC) dominates the forced flow. Moreover, when the flow velocity gradually increases, the primary dendrite spacing decreases from384 to 105 μm accordingly. The simulation results show that the solute distribution at the two sides of the sample can be significantly changed by the forced flow at solidification front. The rejected solute will be unidirectionally transported to one side of the sample along the TEMC(a low-velocity forced flow),thereby causing the formation of a sloping interface. However, the rejected solute will be returned back along the EMC(a higher-velocity force flow), which results in a planar interface. Furthermore, the solute content at the two sides of the sample under the forced flows at different velocities was measured. The results are in good agreement with the simulation results, which shows that the solute content difference between the two sides of the sample reaches the maximum when a 0.5 T TSMF is applied, while the solute content difference decreases to zero with a simultaneous application of a 0.5 T TSMF and a 1.6 × 10~5 A/m^2 external DC.展开更多
Continuous and highly accurate navigation of long-endurance flight vehicles continues to be a substantial challenge in Global Navigation Satellite Systems(GNSS)-denied environments.Though the integrated navigation bas...Continuous and highly accurate navigation of long-endurance flight vehicles continues to be a substantial challenge in Global Navigation Satellite Systems(GNSS)-denied environments.Though the integrated navigation based on multiple sensors is used to improve the navigation performance,the existing methods are prone to model mismatch and error accumulation under heterogeneous conditions of sensors.In this paper,a Tightly-coupled Interactive Multi-Model Factor Graph Optimization(TIMMFGO) navigation method is proposed to solve the problem.The developed integrated navigation framework consists of Inertial Navigation Systems(INS),Celestial Navigation Systems(CNS),Radio Navigation Systems(RNS),and Barometric Altimeters(BA).We propose a CNS/INS tightly-coupled graph architecture that integrates star vector observations with INS pre-integration,enabling dynamic compensation of gyroscopic bias while correcting the attitude update accuracy of INS.Then,an Interactive Multi-Model(IMM) adaptive weighting strategy is used to combine the vertical RNS factor with the BA factor for position,which can effectively reduce the altitude bias induced by the spatial configuration constraints of RNS.The simulation demonstrates that compared to the Huber M-estimation-based FGO(HMFGO),Windowing Anomaly-Detection-based FGO(WADFGO) and IMM Unscented Kalman Filter(IMMUKF)methods,the TIMMFGO method improves attitude accuracy by 46.49 %,25.68 % and 20.67 %,respectively,while correspondingly reducing position accuracy by 29.29 %,10.79 % and 6.96 %.展开更多
基金financially supported by the National Key Research and Development Program of China (No.2016YFB0301401)the National Natural Science Foundation of China (No.U1732276)+1 种基金the Science and Technology Commission of Shanghai Municipality (Key Project Nos.13JC1402500 and 15520711000)the Independent Research and Development Project of State Key of Advanced Special Steel,Shanghai University (Nos.SKLASS2015-Z021 and SELF-2014-02)
文摘The effects of forced flows at different velocities on microstructure and solute distribution during the directional solidification of Sn-10 wt% Bi alloys under a simultaneous imposition of a transverse static magnetic field(TSMF) and an external direct current(DC) have been investigated experimentally and numerically. The experimental results show that the solid-liquid interface will gradually become sloping with the increase of the forced flow velocity when the thermoelectric magnetic convection(TEMC)dominates the forced flow at solidification front. However, the interface will gradually become planar as the flow velocity further increases when the electromagnetic convection(EMC) dominates the forced flow. Moreover, when the flow velocity gradually increases, the primary dendrite spacing decreases from384 to 105 μm accordingly. The simulation results show that the solute distribution at the two sides of the sample can be significantly changed by the forced flow at solidification front. The rejected solute will be unidirectionally transported to one side of the sample along the TEMC(a low-velocity forced flow),thereby causing the formation of a sloping interface. However, the rejected solute will be returned back along the EMC(a higher-velocity force flow), which results in a planar interface. Furthermore, the solute content at the two sides of the sample under the forced flows at different velocities was measured. The results are in good agreement with the simulation results, which shows that the solute content difference between the two sides of the sample reaches the maximum when a 0.5 T TSMF is applied, while the solute content difference decreases to zero with a simultaneous application of a 0.5 T TSMF and a 1.6 × 10~5 A/m^2 external DC.
基金co-supported by the Open Fund of National Natural Science Foundation of China(No.62401042)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(No.2023QNRC001)。
文摘Continuous and highly accurate navigation of long-endurance flight vehicles continues to be a substantial challenge in Global Navigation Satellite Systems(GNSS)-denied environments.Though the integrated navigation based on multiple sensors is used to improve the navigation performance,the existing methods are prone to model mismatch and error accumulation under heterogeneous conditions of sensors.In this paper,a Tightly-coupled Interactive Multi-Model Factor Graph Optimization(TIMMFGO) navigation method is proposed to solve the problem.The developed integrated navigation framework consists of Inertial Navigation Systems(INS),Celestial Navigation Systems(CNS),Radio Navigation Systems(RNS),and Barometric Altimeters(BA).We propose a CNS/INS tightly-coupled graph architecture that integrates star vector observations with INS pre-integration,enabling dynamic compensation of gyroscopic bias while correcting the attitude update accuracy of INS.Then,an Interactive Multi-Model(IMM) adaptive weighting strategy is used to combine the vertical RNS factor with the BA factor for position,which can effectively reduce the altitude bias induced by the spatial configuration constraints of RNS.The simulation demonstrates that compared to the Huber M-estimation-based FGO(HMFGO),Windowing Anomaly-Detection-based FGO(WADFGO) and IMM Unscented Kalman Filter(IMMUKF)methods,the TIMMFGO method improves attitude accuracy by 46.49 %,25.68 % and 20.67 %,respectively,while correspondingly reducing position accuracy by 29.29 %,10.79 % and 6.96 %.
