SATech-01 is an experimental satellite for space science exploration and on-orbit demonstration of advanced technologies.The satellite is equipped with 16 experimental payloads and supports multiple working modes to m...SATech-01 is an experimental satellite for space science exploration and on-orbit demonstration of advanced technologies.The satellite is equipped with 16 experimental payloads and supports multiple working modes to meet the observation requirements of various payloads.Due to the limitation of platform power supply and data storage systems,proposing reasonable mission planning schemes to improve scientific revenue of the payloads becomes a critical issue.In this article,we formulate the integrated task scheduling of SATech-01 as a multi-objective optimization problem and propose a novel Fair Integrated Scheduling with Proximal Policy Optimization(FIS-PPO)algorithm to solve it.We use multiple decision heads to generate decisions for each task and design the action mask to ensure the schedule meeting the platform constraints.Experimental results show that FIS-PPO could push the capability of the platform to the limit and improve the overall observation efficiency by 31.5%compared to rule-based plans currently used.Moreover,fairness is considered in the reward design and our method achieves much better performance in terms of equal task opportunities.Because of its low computational complexity,our task scheduling algorithm has the potential to be directly deployed on board for real-time task scheduling in future space projects.展开更多
利用试验和数值模拟相结合的方法研究6 cm Kaufman离子推力器放电电压和屏栅电压的变化对其工作性能的影响。试验中,离子推力器使用氩气作为推进剂,测量了多组不同工况下的性能参数。此外,基于Goebel的理论模型模拟了放电电压对束流电...利用试验和数值模拟相结合的方法研究6 cm Kaufman离子推力器放电电压和屏栅电压的变化对其工作性能的影响。试验中,离子推力器使用氩气作为推进剂,测量了多组不同工况下的性能参数。此外,基于Goebel的理论模型模拟了放电电压对束流电流和推进剂利用率的影响;采用单元内粒子-蒙特卡罗碰撞(PIC-MCC)方法模拟屏栅电压对束流电流、推进剂利用率和加速栅极电流的影响。试验和数值模拟结果一致,发现当放电电压逐渐增大时,引出的束流电流和推进剂利用率先增加然后趋于稳定;当屏栅电压逐渐增大时,引出的束流电流和推进剂利用率先增加然后趋于稳定,加速栅极电流先减小后趋于稳定。研究可以为提高多模式离子推力器的性能提供参考。展开更多
Two bis-naphthalimide-based supramolecular gelators(NN-3 and NN-4)with a little difference of position of amino groups were designed and synthesized for the detection of oxaloyl chloride and phosgene.Energy transfer c...Two bis-naphthalimide-based supramolecular gelators(NN-3 and NN-4)with a little difference of position of amino groups were designed and synthesized for the detection of oxaloyl chloride and phosgene.Energy transfer could be occurred between two naphthalimide groups in molecules NN-3 and NN-4.Yellow gels NN-3 and NN-4 were formed in some mixed solvents,and nanofibers with different size were obtained in these gels.The self-assembly processes of NN-3 and NN-4 in different solvents were investigated by UV-vis absorption,fluorescent spectra,SEM,FTIR,XRD and NMR.Gelators NN-3 and NN-4 could selectively detect oxaloyl chloride in solution and film states,but detect phosgene only in solution.NN-3exhibited the ratiometric detection ability towards oxaloyl chloride and phosgene with the low limit of detection(LOD)of 210 nmol/L and 90 nmol/L,respectively.NN-4 as the corresponding control sample,it owned the higher LOD towards oxaloyl chloride and phosgene of 12.4μmol/L and 64μmol/L,respectively.Interestingly,films NN-3 and NN-4 could sensitively detect oxaloyl chloride gases with the low LOD of2.0 ppm and 8.34 ppm,respectively.The detection mechanisms of NN-3 and NN-4 were well studied by1H NMR titration,HRMS and theoretical calculation.展开更多
The traditional stochastic homogenization method can obtain homogenized solutions of elliptic problems with stationary random coefficients.However,many random composite materials in scientific and engineering computin...The traditional stochastic homogenization method can obtain homogenized solutions of elliptic problems with stationary random coefficients.However,many random composite materials in scientific and engineering computing do not satisfy the stationary assumption.To overcome the difficulty,we propose a normalizing field flow induced two-stage stochastic homogenization method to efficiently solve the random elliptic problem with non-stationary coefficients.By applying the two-stage stochastic homogenization method,the original elliptic equation with random and fast oscillatory coefficients is approximated as an equivalent elliptic equation,where the equivalent coefficients are obtained by solving a set of cell problems.Without the stationary assumption,the number of cell problems is large and the corresponding computational cost is high.To improve the efficiency,we apply the normalizing field flow model to learn a reference Gaussian field for the random equivalent coefficients based on a small amount of data,which is obtained by solving the cell problems with the finite element method.Numerical results demonstrate that the newly proposed method is efficient and accurate in tackling high dimensional partial differential equations in composite materials with complex random microstructures.展开更多
In many geophysical applications, neglecting of anisotropy is somehow an oversimplification. The mismatch between prediction based on isotropic theory and near-surface seismic observations indicates the need for the i...In many geophysical applications, neglecting of anisotropy is somehow an oversimplification. The mismatch between prediction based on isotropic theory and near-surface seismic observations indicates the need for the inclusion of medium anisotropy. In this paper, surface wave（Love wave） dispersion properties are used to estimate the anisotropic structure of the near-surface layered earth, which is modeled as media possess vertical transverse isotropy（VTI）, a reasonable assumption for near-surface sedimentary layers. Our approach utilizes multi-mode surface waves to estimate both the velocity structure and the anisotropy structure. This approach consists of three parts. First, the dispersion analysis is used to extract dispersion curves from real data. Second, the forward modeling is carried out based on the dispersion equation of Love wave in a multi-layered VTI medium. Dispersion curves of multi-modes, which are the numerical solutions of the dispersion equation, are obtained by a graphic-based method. Finally, the very fast simulated annealing（VFSA） algorithm is used to invert velocity structure and anisotropy structure simultaneously. Our approach is verified by the synthetic dispersion curve generated by a VTI medium model. The estimation of shear wave velocity and anisotropy structure of surface wave data acquired at Rentschler Field, an urban center site on sediments in the Connecticut River valley reveals a simple structure of the sediment layer over a bedrock half space. The results are verified by other inversion results based on different data set obtained on the same site. The consistency of inversion results shows the feasibility and efficiency of the approach.展开更多
A complex product subjects to multiple failure modes such as minor and catastrophic failure with some probability.This paper investigates the effects of minor failure and catastrophic failure on the periodic replaceme...A complex product subjects to multiple failure modes such as minor and catastrophic failure with some probability.This paper investigates the effects of minor failure and catastrophic failure on the periodic replacement policy for a complex product supported by a warranty period.Cost models are developed and the expected optimal replacement policies are developed analytically such that long run expected life-cycle cost rate is minimized.Structural properties of the optimal replacement policies are derived for a product which fails with multiple failure modes and the failure rate is an increasing function of time.Finally,a numerical experiment is performed to show the important features of our study.展开更多
基金supported by the Strategic Priority Program on Space Science,Chinese Academy of Sciences。
文摘SATech-01 is an experimental satellite for space science exploration and on-orbit demonstration of advanced technologies.The satellite is equipped with 16 experimental payloads and supports multiple working modes to meet the observation requirements of various payloads.Due to the limitation of platform power supply and data storage systems,proposing reasonable mission planning schemes to improve scientific revenue of the payloads becomes a critical issue.In this article,we formulate the integrated task scheduling of SATech-01 as a multi-objective optimization problem and propose a novel Fair Integrated Scheduling with Proximal Policy Optimization(FIS-PPO)algorithm to solve it.We use multiple decision heads to generate decisions for each task and design the action mask to ensure the schedule meeting the platform constraints.Experimental results show that FIS-PPO could push the capability of the platform to the limit and improve the overall observation efficiency by 31.5%compared to rule-based plans currently used.Moreover,fairness is considered in the reward design and our method achieves much better performance in terms of equal task opportunities.Because of its low computational complexity,our task scheduling algorithm has the potential to be directly deployed on board for real-time task scheduling in future space projects.
文摘利用试验和数值模拟相结合的方法研究6 cm Kaufman离子推力器放电电压和屏栅电压的变化对其工作性能的影响。试验中,离子推力器使用氩气作为推进剂,测量了多组不同工况下的性能参数。此外,基于Goebel的理论模型模拟了放电电压对束流电流和推进剂利用率的影响;采用单元内粒子-蒙特卡罗碰撞(PIC-MCC)方法模拟屏栅电压对束流电流、推进剂利用率和加速栅极电流的影响。试验和数值模拟结果一致,发现当放电电压逐渐增大时,引出的束流电流和推进剂利用率先增加然后趋于稳定;当屏栅电压逐渐增大时,引出的束流电流和推进剂利用率先增加然后趋于稳定,加速栅极电流先减小后趋于稳定。研究可以为提高多模式离子推力器的性能提供参考。
基金financially supported by the National Natural Science Foundation of China(No.U1704164)the Basic Research Project of Henan Provincial Key Scientific Research Project(No.22ZX002)。
文摘Two bis-naphthalimide-based supramolecular gelators(NN-3 and NN-4)with a little difference of position of amino groups were designed and synthesized for the detection of oxaloyl chloride and phosgene.Energy transfer could be occurred between two naphthalimide groups in molecules NN-3 and NN-4.Yellow gels NN-3 and NN-4 were formed in some mixed solvents,and nanofibers with different size were obtained in these gels.The self-assembly processes of NN-3 and NN-4 in different solvents were investigated by UV-vis absorption,fluorescent spectra,SEM,FTIR,XRD and NMR.Gelators NN-3 and NN-4 could selectively detect oxaloyl chloride in solution and film states,but detect phosgene only in solution.NN-3exhibited the ratiometric detection ability towards oxaloyl chloride and phosgene with the low limit of detection(LOD)of 210 nmol/L and 90 nmol/L,respectively.NN-4 as the corresponding control sample,it owned the higher LOD towards oxaloyl chloride and phosgene of 12.4μmol/L and 64μmol/L,respectively.Interestingly,films NN-3 and NN-4 could sensitively detect oxaloyl chloride gases with the low LOD of2.0 ppm and 8.34 ppm,respectively.The detection mechanisms of NN-3 and NN-4 were well studied by1H NMR titration,HRMS and theoretical calculation.
基金supported by the National Natural Science Foundation of China grant(12131002,51739007,12271409)Strategic Priority Research Program of the Chinese Academy of Sciences(XDC06030101)+2 种基金the National Key R&D Program of China with the grant(2020YFA-0713603)Natural Science Foundation of Shanghai grant(21ZR1465800)the Interdisciplinary Project in Ocean Research of Tongji University and the Fundamental Research Funds for the Central Universities..
文摘The traditional stochastic homogenization method can obtain homogenized solutions of elliptic problems with stationary random coefficients.However,many random composite materials in scientific and engineering computing do not satisfy the stationary assumption.To overcome the difficulty,we propose a normalizing field flow induced two-stage stochastic homogenization method to efficiently solve the random elliptic problem with non-stationary coefficients.By applying the two-stage stochastic homogenization method,the original elliptic equation with random and fast oscillatory coefficients is approximated as an equivalent elliptic equation,where the equivalent coefficients are obtained by solving a set of cell problems.Without the stationary assumption,the number of cell problems is large and the corresponding computational cost is high.To improve the efficiency,we apply the normalizing field flow model to learn a reference Gaussian field for the random equivalent coefficients based on a small amount of data,which is obtained by solving the cell problems with the finite element method.Numerical results demonstrate that the newly proposed method is efficient and accurate in tackling high dimensional partial differential equations in composite materials with complex random microstructures.
基金supported by the U.S. Geological Survey through a research collaboration program with University of Connecticut via its branch of geophysics, office of groundwater
文摘In many geophysical applications, neglecting of anisotropy is somehow an oversimplification. The mismatch between prediction based on isotropic theory and near-surface seismic observations indicates the need for the inclusion of medium anisotropy. In this paper, surface wave（Love wave） dispersion properties are used to estimate the anisotropic structure of the near-surface layered earth, which is modeled as media possess vertical transverse isotropy（VTI）, a reasonable assumption for near-surface sedimentary layers. Our approach utilizes multi-mode surface waves to estimate both the velocity structure and the anisotropy structure. This approach consists of three parts. First, the dispersion analysis is used to extract dispersion curves from real data. Second, the forward modeling is carried out based on the dispersion equation of Love wave in a multi-layered VTI medium. Dispersion curves of multi-modes, which are the numerical solutions of the dispersion equation, are obtained by a graphic-based method. Finally, the very fast simulated annealing（VFSA） algorithm is used to invert velocity structure and anisotropy structure simultaneously. Our approach is verified by the synthetic dispersion curve generated by a VTI medium model. The estimation of shear wave velocity and anisotropy structure of surface wave data acquired at Rentschler Field, an urban center site on sediments in the Connecticut River valley reveals a simple structure of the sediment layer over a bedrock half space. The results are verified by other inversion results based on different data set obtained on the same site. The consistency of inversion results shows the feasibility and efficiency of the approach.
基金This work was supported by the National Natural Science Foundation of China under grant numbers 71531010 and 71831006.
文摘A complex product subjects to multiple failure modes such as minor and catastrophic failure with some probability.This paper investigates the effects of minor failure and catastrophic failure on the periodic replacement policy for a complex product supported by a warranty period.Cost models are developed and the expected optimal replacement policies are developed analytically such that long run expected life-cycle cost rate is minimized.Structural properties of the optimal replacement policies are derived for a product which fails with multiple failure modes and the failure rate is an increasing function of time.Finally,a numerical experiment is performed to show the important features of our study.
