To carry out the deep space exploration tasks near Sun-Earth Libration point L2, the CRTBP dynamic model was built up and the numerical conditional quasi-periodic orbit （Lissajons orbit） was computed near L2. Then, ...To carry out the deep space exploration tasks near Sun-Earth Libration point L2, the CRTBP dynamic model was built up and the numerical conditional quasi-periodic orbit （Lissajons orbit） was computed near L2. Then, a formation controller was designed with linear matrix inequality to overcome the difficuhy of parameter tuning. To meet the demands of formation accuracy and present thruster＇s capability, a threshold scheme was adopted for formation control. Finally, some numerical simulations and analysis were completed to demonstrate the feasibility of the proposed control strategy.展开更多
In this work, a new mathematical modelling of drying kinetics is described. At first, the modelling of the transfer speed （St） of water was performed. Then St was used as basis to state the drying rate model. The dr...In this work, a new mathematical modelling of drying kinetics is described. At first, the modelling of the transfer speed （St） of water was performed. Then St was used as basis to state the drying rate model. The drying rate depends not only on drying time, but also on some modelling parameters which are themselves time-dependent. All the modelling parameters are calculated directly from the experimental drying data. Then the theoretical model of the moisture content was stated. Subsequently, the drying kinetics of natural solar drying of plantain banana was studied as illustration. The drying rate was investigated. The comparison with other models encountered in literatures proved that the current theoretical model was decidedly more accurate. Then the modelling of moisture content of banana was performed and the results were compared with the Henderson and Pabis model. The current theoretical modelling provided by far the best fit.展开更多
This paper presents an improved space-time conservation element and solution element(CESE)method by applying a non-staggered space-time mesh system and simply improving the calculation of flow variables and applies it...This paper presents an improved space-time conservation element and solution element(CESE)method by applying a non-staggered space-time mesh system and simply improving the calculation of flow variables and applies it to magnetohydrodynamics(MHD)equations.The improved CESE method can improve the solution quality even with a large disparity in the Courant number(CFL)when using a fixed global marching time.Moreover,for a small CFL(say<0.1),the method can significantly reduce the numerical dissipation and retain the solution quality,which are verified by two benchmark problems.And meanwhile,comparison with the original CESE scheme shows better resolution of the improved scheme results.Finally,we demonstrate its validation through the application of this method in three-dimensional coronal dynamical structure with dipole magnetic fields and measured solar surface magnetic fields as the initial input.展开更多
Researchers working in the field of photovoltaic are exploring novel materials for the efficient solar energy conversion.The prime objective of the discovery of every novel photovoltaic material is to achieve more ene...Researchers working in the field of photovoltaic are exploring novel materials for the efficient solar energy conversion.The prime objective of the discovery of every novel photovoltaic material is to achieve more energy yield with easy fabrication process and less production cost features.Perovskite solar cells (PSCs)delivering the highest efficiency in the passing years with different stoichiometry and fabrication modification have made this technology a potent candidate for future energy conversion materials.Till now,many studies have shown that the quality of active layer morphology,to a great extent,determines the performance of PSCs.The current and potential techniques of solvent engineering for good active layer morphology are mainly debated using primary solvent,co-solvent (Lewis acid-base adduct approach)and solvent additives.In this review,the dynamics of numerously reported solvents on the morphological characteristics of PSCs active layer are discussed in detail.The intention is to get a clear understanding of solvent engineering induced modifications on active layer morphology in PSC devices via different crystallization routes.At last,an attempt is made to draw a framework based on different solvent coordination properties to make it easy for screening the potent solvent contender for desired PSCs precursor for a better and feasible device.展开更多
The topology and dynamics of the three-dimensional magnetic field in the solar atmosphere govern various solar eruptive phenomena and activities, such as flares, coronal mass ejections, and filaments/prominences. We h...The topology and dynamics of the three-dimensional magnetic field in the solar atmosphere govern various solar eruptive phenomena and activities, such as flares, coronal mass ejections, and filaments/prominences. We have to observe and model the vector magnetic field to understand the structures and physical mechanisms of these solar activities. Vector magnetic fields on the photosphere are routinely observed via the polarized light, and inferred with the inversion of Stokes profiles. To analyze these vector magnetic fields, we need first to remove the 180° ambiguity of the transverse components and correct the projection effect. Then, the vector magnetic field can be served as the boundary conditions for a force-free field modeling after a proper preprocessing. The photospheric velocity field can also be derived from a time sequence of vector magnetic fields.Three-dimensional magnetic field could be derived and studied with theoretical force-free field models, numerical nonlinear force-free field models, magnetohydrostatic models, and magnetohydrodynamic models. Magnetic energy can be computed with three-dimensional magnetic field models or a time series of vector magnetic field. The magnetic topology is analyzed by pinpointing the positions of magnetic null points, bald patches, and quasi-separatrix layers. As a well conserved physical quantity,magnetic helicity can be computed with various methods, such as the finite volume method, discrete flux tube method, and helicity flux integration method. This quantity serves as a promising parameter characterizing the activity level of solar active regions.展开更多
The optimal control problem of the multibody dynamics of a spacecraft in space, modeled as a central body with one-sided connected deployable solar arrays, is investigated. The dynamical equations of motion of the spa...The optimal control problem of the multibody dynamics of a spacecraft in space, modeled as a central body with one-sided connected deployable solar arrays, is investigated. The dynamical equations of motion of the spacecraft with solar arrays are derived using the multibody dynamics method. The control of the attitude motion of a spacecraft system can be transformed into the motion planning problem of nonholonomic system when the initial angular momentum is zero. These are then used to investigate the motion planning of the spacecraft during solar arrays deployment via particle swarm optimization (PSO) and results are obtained with the optimal control input and the optimal trajectory. The results of numerical simulation show that this approach is effective for the control problem of the attitude of a spacecraft during the deployment process of its solar arrays.展开更多
文摘To carry out the deep space exploration tasks near Sun-Earth Libration point L2, the CRTBP dynamic model was built up and the numerical conditional quasi-periodic orbit （Lissajons orbit） was computed near L2. Then, a formation controller was designed with linear matrix inequality to overcome the difficuhy of parameter tuning. To meet the demands of formation accuracy and present thruster＇s capability, a threshold scheme was adopted for formation control. Finally, some numerical simulations and analysis were completed to demonstrate the feasibility of the proposed control strategy.
文摘In this work, a new mathematical modelling of drying kinetics is described. At first, the modelling of the transfer speed （St） of water was performed. Then St was used as basis to state the drying rate model. The drying rate depends not only on drying time, but also on some modelling parameters which are themselves time-dependent. All the modelling parameters are calculated directly from the experimental drying data. Then the theoretical model of the moisture content was stated. Subsequently, the drying kinetics of natural solar drying of plantain banana was studied as illustration. The drying rate was investigated. The comparison with other models encountered in literatures proved that the current theoretical model was decidedly more accurate. Then the modelling of moisture content of banana was performed and the results were compared with the Henderson and Pabis model. The current theoretical modelling provided by far the best fit.
基金supported by the National Basic Research Program of China(Grant No.2012CB825601)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZZD-EW-01-4)+1 种基金the National Natural Science Foundation of China(Grant Nos.41031066,41231068,41074121&41074122)the Specialized Research Fund for State Key Laboratories
文摘This paper presents an improved space-time conservation element and solution element(CESE)method by applying a non-staggered space-time mesh system and simply improving the calculation of flow variables and applies it to magnetohydrodynamics(MHD)equations.The improved CESE method can improve the solution quality even with a large disparity in the Courant number(CFL)when using a fixed global marching time.Moreover,for a small CFL(say<0.1),the method can significantly reduce the numerical dissipation and retain the solution quality,which are verified by two benchmark problems.And meanwhile,comparison with the original CESE scheme shows better resolution of the improved scheme results.Finally,we demonstrate its validation through the application of this method in three-dimensional coronal dynamical structure with dipole magnetic fields and measured solar surface magnetic fields as the initial input.
基金supported by the National Key Research and Development Program of China (2016YFA0202400)the 111 project (B16016)the National Natural Science Foundation of China (51572080, 51702096, and U1705256)
文摘Researchers working in the field of photovoltaic are exploring novel materials for the efficient solar energy conversion.The prime objective of the discovery of every novel photovoltaic material is to achieve more energy yield with easy fabrication process and less production cost features.Perovskite solar cells (PSCs)delivering the highest efficiency in the passing years with different stoichiometry and fabrication modification have made this technology a potent candidate for future energy conversion materials.Till now,many studies have shown that the quality of active layer morphology,to a great extent,determines the performance of PSCs.The current and potential techniques of solvent engineering for good active layer morphology are mainly debated using primary solvent,co-solvent (Lewis acid-base adduct approach)and solvent additives.In this review,the dynamics of numerously reported solvents on the morphological characteristics of PSCs active layer are discussed in detail.The intention is to get a clear understanding of solvent engineering induced modifications on active layer morphology in PSC devices via different crystallization routes.At last,an attempt is made to draw a framework based on different solvent coordination properties to make it easy for screening the potent solvent contender for desired PSCs precursor for a better and feasible device.
基金supported by National Natural Science Foundation of China (Grant Nos. 11533005, 11203014, 11373023, and 11303016)National Key Basic Research Special Foundation (Grant No. 2014CB744203)
文摘The topology and dynamics of the three-dimensional magnetic field in the solar atmosphere govern various solar eruptive phenomena and activities, such as flares, coronal mass ejections, and filaments/prominences. We have to observe and model the vector magnetic field to understand the structures and physical mechanisms of these solar activities. Vector magnetic fields on the photosphere are routinely observed via the polarized light, and inferred with the inversion of Stokes profiles. To analyze these vector magnetic fields, we need first to remove the 180° ambiguity of the transverse components and correct the projection effect. Then, the vector magnetic field can be served as the boundary conditions for a force-free field modeling after a proper preprocessing. The photospheric velocity field can also be derived from a time sequence of vector magnetic fields.Three-dimensional magnetic field could be derived and studied with theoretical force-free field models, numerical nonlinear force-free field models, magnetohydrostatic models, and magnetohydrodynamic models. Magnetic energy can be computed with three-dimensional magnetic field models or a time series of vector magnetic field. The magnetic topology is analyzed by pinpointing the positions of magnetic null points, bald patches, and quasi-separatrix layers. As a well conserved physical quantity,magnetic helicity can be computed with various methods, such as the finite volume method, discrete flux tube method, and helicity flux integration method. This quantity serves as a promising parameter characterizing the activity level of solar active regions.
基金supported by the National Natural Science Foundation of China (Grant No. 11072038)
文摘The optimal control problem of the multibody dynamics of a spacecraft in space, modeled as a central body with one-sided connected deployable solar arrays, is investigated. The dynamical equations of motion of the spacecraft with solar arrays are derived using the multibody dynamics method. The control of the attitude motion of a spacecraft system can be transformed into the motion planning problem of nonholonomic system when the initial angular momentum is zero. These are then used to investigate the motion planning of the spacecraft during solar arrays deployment via particle swarm optimization (PSO) and results are obtained with the optimal control input and the optimal trajectory. The results of numerical simulation show that this approach is effective for the control problem of the attitude of a spacecraft during the deployment process of its solar arrays.
