Nighttime navigation faces challenges from limited data and interference,especially when satellite signals are unavailable.Leveraging lunar polarized light,polarization navigation offers a promising solution for night...Nighttime navigation faces challenges from limited data and interference,especially when satellite signals are unavailable.Leveraging lunar polarized light,polarization navigation offers a promising solution for nighttime autonomous navigation.Current algorithms,however,are limited by the requirement for known horizontal attitudes,restricting applications.This study introduces an autonomous 3-D attitude determination method to overcome this limitation.Our approach utilizes the Angle of Polarization(AOP)at night to extract neutral points from the AOP pattern.This allows for the calculation of polarization meridian plane information for attitude determination.Subsequently,we present an optimized Polarization TRIAD(Pol-TRIAD)algorithm to acquire the 3-D attitude.The proposed method outperforms the existing approaches in outdoor experiments by achieving lower Root Mean Square Error(RMSE).For one baseline attitude,it improves pitch by 31.7%,roll by 21.7%,and yaw by 2.6%,while for the attitude with a larger tilt angle,the improvements are 64.4%,30.4%,and 9.1%,respectively.展开更多
The attitude control problem and the guidance problem are solved in 3-D for a buoyancy-driven airship actuated by the combined effects of an internal air bladder which modulates the airshiprs net weight and of two mov...The attitude control problem and the guidance problem are solved in 3-D for a buoyancy-driven airship actuated by the combined effects of an internal air bladder which modulates the airshiprs net weight and of two moving masses which modulate its center of mass. A simple and clear modeling is introduced to derive the 8 degree of freedom （DOF） mathematical model. Nonlinear control loops are derived through maximal feedback linearization with internal stability for both dynamics in the longitudinal plane and in the lateral plane. Based on a singular perturbation approach, the superposition of these two control actions in the longitudinal plane and in the lateral plane is shown to achieve the control of the dynamics in 3-D space. The simulations of the airship tracking specified attitude, moving direction and speed in 3-D space are presented.展开更多
Aiming to address the Unmanned Aerial Vehicle(UAV) formation collision avoidance problem in Three-Dimensional(3-D) low-altitude environments where dense various obstacles exist, a fluid-based path planning framework n...Aiming to address the Unmanned Aerial Vehicle(UAV) formation collision avoidance problem in Three-Dimensional(3-D) low-altitude environments where dense various obstacles exist, a fluid-based path planning framework named the Formation Interfered Fluid Dynamical System(FIFDS) with Moderate Evasive Maneuver Strategy(MEMS) is proposed in this study.First, the UAV formation collision avoidance problem including quantifiable performance indexes is formulated. Second, inspired by the phenomenon of fluids continuously flowing while bypassing objects, the FIFDS for multiple UAVs is presented, which contains a Parallel Streamline Tracking(PST) method for formation keeping and the traditional IFDS for collision avoidance. Third, to rationally balance flight safety and collision avoidance cost, MEMS is proposed to generate moderate evasive maneuvers that match up with collision risks. Comprehensively containing the time and distance safety information, the 3-D dynamic collision regions are modeled for collision prediction. Then, the moderate evasive maneuver principle is refined, which provides criterions of the maneuver amplitude and direction. On this basis, an analytical parameter mapping mechanism is designed to online optimize IFDS parameters. Finally, the performance of the proposed method is validated by comparative simulation results and real flight experiments using fixed-wing UAVs.展开更多
Ethnic mountain settlements are living heritage of varied vernacular cultures.The preservation of both the built form and the intangible socio-cultural associations with them are global concern in process of urbanizat...Ethnic mountain settlements are living heritage of varied vernacular cultures.The preservation of both the built form and the intangible socio-cultural associations with them are global concern in process of urbanization,and in the notion of sustainable development.However,there is a lack of multi-dimensional and cross-cultural quantitative research in settlement morphology,making it difficult to guide practice effectively.Therefore,this study focuses on exploring an automatic or semi-automatic quantification and classification method for the morphological identity of ethnic mountain settlements.We introduce and combine 3-D morphological indicators with existing 2-D indicators to build and test three different sets of indication systems for semi-automatic classification for the settlements’ethnic attribute basing on spatial morphology.Taking the Miao,Dong,and Tunpu(Han)ethnic settlements in Guizhou province,southwest China as research samples,we applied factor analysis and hierarchical clustering methods to compare the classification accuracy under the three systems using data from topographic map,field investigation map,satellite imageries,and ethnography or local chronicle.The results showed that,the 3-D indication system has succeeded in semi-automatic quantification and classification of settlement morphology and ethnic identity by greatly increasing the classification accuracy to 96.30%,which is a huge improvement compared with the basic 2-D indication system(42.59%)and the advanced 2-D indication system(61.11%).The settlement samples are further divided into two sub-types with significant morphological differences in each major ethnic category under the 3-D indication system.We then discussed the potential improvement and future large-scale application of this method with the help of machine learning and other smart techniques.We hope to provide a comprehensive quantitative perspective and a more scientific reference for the future preservation and sustainable development of the massive and diverse vernacular heritages across the world.展开更多
Microwave-assisted rock-breaking technology,as a novel hybrid approach,is anticipated to facilitate the efficient excavation of complex rock formations.It is therefore crucial to understand the damage and failure mech...Microwave-assisted rock-breaking technology,as a novel hybrid approach,is anticipated to facilitate the efficient excavation of complex rock formations.It is therefore crucial to understand the damage and failure mechanisms of rocks that have been subjected to irradiation.In this study,uniaxial compression experiments were conducted on granite specimens after 1.4 kW microwave irradiation for varying durations.Furthermore,a numerical method was proposed to solve electromagnetic-thermal-mechanical coupling problems by integrating finite and discrete elements.The results demonstrated a differential temperature distribution(high temperature in the middle and low-temperature areas at the ends)in the granite specimens under microwave irradiation,which resulted in a notable reduction in their physical and mechanical properties.As the duration of irradiation increased,the rate of heating and the extent of strength reduction both diminished,while the morphology and distribution of cracks at ultimate failure became increasingly complex.The numerical method effectively addresses the simulation challenges associated with the electromagnetic selective heating of granite containing multiple polar minerals under microwave irradiation.This approach accounted for the non-uniform thermal expansion of the minerals and provided a comprehensive model of damage progression under compression.展开更多
A accelerated arithmetic algorithm of the dynamic computing regions was designed,and 3-dimensional numerical simulation of isothermal solidification for a binary alloy was implemented.The dendritic growth and the reca...A accelerated arithmetic algorithm of the dynamic computing regions was designed,and 3-dimensional numerical simulation of isothermal solidification for a binary alloy was implemented.The dendritic growth and the recalescence of Ni-Cu binary alloy during the solidification at different cooling rates were investigated.The effects of cooling rate on dendritic patterns and microsegregation patterns were studied.The computed results indicate that,with the increment of the cooling rate,the dendritic growth velocity increases,both the main branch and side-branches become slender,the secondary dendrite arm spacing becomes smaller,the inadequate solute diffusion in solid aggravates,and the severity of microsegregation ahead of interface aggravates.At a higher cooling rate,the binary alloy presents recalescence;while the cooling rate is small,no recalescence occurs.展开更多
Accurate 3-dimensional(3-D)reconstruction technology for nondestructive testing based on digital radiography(DR)is of great importance for alleviating the drawbacks of the existing computed tomography(CT)-based method...Accurate 3-dimensional(3-D)reconstruction technology for nondestructive testing based on digital radiography(DR)is of great importance for alleviating the drawbacks of the existing computed tomography(CT)-based method.The commonly used Monte Carlo simulation method ensures well-performing imaging results for DR.However,for 3-D reconstruction,it is limited by its high time consumption.To solve this problem,this study proposes a parallel computing method to accelerate Monte Carlo simulation for projection images with a parallel interface and a specific DR application.The images are utilized for 3-D reconstruction of the test model.We verify the accuracy of parallel computing for DR and evaluate the performance of two parallel computing modes-multithreaded applications(G4-MT)and message-passing interfaces(G4-MPI)-by assessing parallel speedup and efficiency.This study explores the scalability of the hybrid G4-MPI and G4-MT modes.The results show that the two parallel computing modes can significantly reduce the Monte Carlo simulation time because the parallel speedup increment of Monte Carlo simulations can be considered linear growth,and the parallel efficiency is maintained at a high level.The hybrid mode has strong scalability,as the overall run time of the 180 simulations using 320 threads is 15.35 h with 10 billion particles emitted,and the parallel speedup can be up to 151.36.The 3-D reconstruction of the model is achieved based on the filtered back projection(FBP)algorithm using 180 projection images obtained with the hybrid G4-MPI and G4-MT.The quality of the reconstructed sliced images is satisfactory because the images can reflect the internal structure of the test model.This method is applied to a complex model,and the quality of the reconstructed images is evaluated.展开更多
The （3＋1）-dimensional Jimbo-Miwa （JM） equation is solved approximately by using the conformal invariant asymptotic expansion approach presented by Ruan. By solving the new （3＋1）-dimensional integrable models, ...The （3＋1）-dimensional Jimbo-Miwa （JM） equation is solved approximately by using the conformal invariant asymptotic expansion approach presented by Ruan. By solving the new （3＋1）-dimensional integrable models, which are conformal invariant and possess Painlevé property, the approximate solutions are obtained for the JM equation, containing not only one-soliton solutions but also periodic solutions and multi-soliton solutions. Some approximate solutions happen to be exact and some approximate solutions can become exact by choosing relations between the parameters properly.展开更多
In this paper, the entangled mapping approach （EMA） is applied to obtain variable separation solutions of （1＋1）-dimensional and （3＋1）-dimensional systems. By analysis, we firstly find that there also exists a ...In this paper, the entangled mapping approach （EMA） is applied to obtain variable separation solutions of （1＋1）-dimensional and （3＋1）-dimensional systems. By analysis, we firstly find that there also exists a common formula to describe suitable physical fields or potentials for these （1＋1）-dimensional models such as coupled integrable dispersionless （CID） and shallow water wave equations. Moreover, we find that the variable separation solution of the （3＋1）-dimensional Burgers system satisfies the completely same form as the universal quantity U1 in （2＋1）-dimensional systems. The only difference is that the function q is a solution of a constraint equation and p is an arbitrary function of three independent variables.展开更多
The rapid identification of γ-emitting radionuclides with low activity levels in public areas is crucial for nuclear safety.However,classical methods rely on full-energy peaks in the integral spectrum,requiring suffi...The rapid identification of γ-emitting radionuclides with low activity levels in public areas is crucial for nuclear safety.However,classical methods rely on full-energy peaks in the integral spectrum,requiring sufficient count accumulation for evaluation,thereby limiting response time.The sequential Bayesian approach,which utilizes prior information and considers both photon energies and interarrival times,can significantly enhance the performance of radionuclides identification.This study proposes a theoretical optimization method for the traditional sequential Bayesian approach.Each photon is processed sequentially,and the corresponding posterior probability is updated in real time using a noninformative prior from the Bayesian theory.By comparing the posterior probabilities of the background and radionuclides based on the energy variance and time interval,the type of γ-rays can be identified(background characteristic γ-rays,Compton plateaus γ-rays,or radionuclide-specific characteristic γ-rays).By integrating the information from these multiple characteristic γ-rays,the presence and type of radionuclides were determined based on the final decision function and a set threshold.Based on theoretical research,verification experiments were conducted using a LaBr_(3)(Ce)detector in both low-and natural background radiation environments with typical radionuclides(^(137)Cs,^(60)Co,and ^(133)Ba).The results show that this approach can identify ^(137)Cs in 7.9 s and 8.5 s(source dose rate contribution:approximately 6.5×10^(−3)μGy/h),^(60)Co in 8.1 s and 9.8 s(approximately 4.8×10^(−2)μGy/h),and ^(133)Ba in 4.05 s and 5.99 s(approximately 3.4×10^(−2)μGy/h)under low and natural background radiation,respectively,with a miss rate below 0.01%.This demonstrates the effectiveness of the proposed approach for fast radionuclides identification,even at low activity levels and highlights its potential for enhancing public safety in diverse radiation environments.展开更多
基金supported in part by the National Key Research and Development Program of China(Nos.2020YFA0711200,2022YFB4701301)in part by the Defense Industrial Technology Development Program,China(No.JCKY2021601B016)+1 种基金in part by the Fundamental Research Funds for the Central Universities,China(No.YWF-23-JC-07)in part by the National Natural Science Foundation of China(No.62425302)。
文摘Nighttime navigation faces challenges from limited data and interference,especially when satellite signals are unavailable.Leveraging lunar polarized light,polarization navigation offers a promising solution for nighttime autonomous navigation.Current algorithms,however,are limited by the requirement for known horizontal attitudes,restricting applications.This study introduces an autonomous 3-D attitude determination method to overcome this limitation.Our approach utilizes the Angle of Polarization(AOP)at night to extract neutral points from the AOP pattern.This allows for the calculation of polarization meridian plane information for attitude determination.Subsequently,we present an optimized Polarization TRIAD(Pol-TRIAD)algorithm to acquire the 3-D attitude.The proposed method outperforms the existing approaches in outdoor experiments by achieving lower Root Mean Square Error(RMSE).For one baseline attitude,it improves pitch by 31.7%,roll by 21.7%,and yaw by 2.6%,while for the attitude with a larger tilt angle,the improvements are 64.4%,30.4%,and 9.1%,respectively.
基金Supported by the Scholarship Foundation of China Scholarship Council~~
文摘The attitude control problem and the guidance problem are solved in 3-D for a buoyancy-driven airship actuated by the combined effects of an internal air bladder which modulates the airshiprs net weight and of two moving masses which modulate its center of mass. A simple and clear modeling is introduced to derive the 8 degree of freedom （DOF） mathematical model. Nonlinear control loops are derived through maximal feedback linearization with internal stability for both dynamics in the longitudinal plane and in the lateral plane. Based on a singular perturbation approach, the superposition of these two control actions in the longitudinal plane and in the lateral plane is shown to achieve the control of the dynamics in 3-D space. The simulations of the airship tracking specified attitude, moving direction and speed in 3-D space are presented.
基金supported in part by the National Natural Science Foundations of China(Nos.61175084,61673042 and 62203046)the China Postdoctoral Science Foundation(No.2022M713006).
文摘Aiming to address the Unmanned Aerial Vehicle(UAV) formation collision avoidance problem in Three-Dimensional(3-D) low-altitude environments where dense various obstacles exist, a fluid-based path planning framework named the Formation Interfered Fluid Dynamical System(FIFDS) with Moderate Evasive Maneuver Strategy(MEMS) is proposed in this study.First, the UAV formation collision avoidance problem including quantifiable performance indexes is formulated. Second, inspired by the phenomenon of fluids continuously flowing while bypassing objects, the FIFDS for multiple UAVs is presented, which contains a Parallel Streamline Tracking(PST) method for formation keeping and the traditional IFDS for collision avoidance. Third, to rationally balance flight safety and collision avoidance cost, MEMS is proposed to generate moderate evasive maneuvers that match up with collision risks. Comprehensively containing the time and distance safety information, the 3-D dynamic collision regions are modeled for collision prediction. Then, the moderate evasive maneuver principle is refined, which provides criterions of the maneuver amplitude and direction. On this basis, an analytical parameter mapping mechanism is designed to online optimize IFDS parameters. Finally, the performance of the proposed method is validated by comparative simulation results and real flight experiments using fixed-wing UAVs.
基金supported by the National Key R&D Program of China(No.2018YFD1100303)。
文摘Ethnic mountain settlements are living heritage of varied vernacular cultures.The preservation of both the built form and the intangible socio-cultural associations with them are global concern in process of urbanization,and in the notion of sustainable development.However,there is a lack of multi-dimensional and cross-cultural quantitative research in settlement morphology,making it difficult to guide practice effectively.Therefore,this study focuses on exploring an automatic or semi-automatic quantification and classification method for the morphological identity of ethnic mountain settlements.We introduce and combine 3-D morphological indicators with existing 2-D indicators to build and test three different sets of indication systems for semi-automatic classification for the settlements’ethnic attribute basing on spatial morphology.Taking the Miao,Dong,and Tunpu(Han)ethnic settlements in Guizhou province,southwest China as research samples,we applied factor analysis and hierarchical clustering methods to compare the classification accuracy under the three systems using data from topographic map,field investigation map,satellite imageries,and ethnography or local chronicle.The results showed that,the 3-D indication system has succeeded in semi-automatic quantification and classification of settlement morphology and ethnic identity by greatly increasing the classification accuracy to 96.30%,which is a huge improvement compared with the basic 2-D indication system(42.59%)and the advanced 2-D indication system(61.11%).The settlement samples are further divided into two sub-types with significant morphological differences in each major ethnic category under the 3-D indication system.We then discussed the potential improvement and future large-scale application of this method with the help of machine learning and other smart techniques.We hope to provide a comprehensive quantitative perspective and a more scientific reference for the future preservation and sustainable development of the massive and diverse vernacular heritages across the world.
基金funded by the Postgraduate Research and Practice Innovation Program of Jiangsu Province(Grant No.KYCX23_2744)the Fundamental Research Funds for the Central Universities(Grant No.2023XSCX051)the Graduate Innovation Program of China University of Mining and Technology(Grant No.2023WLKXJ182).
文摘Microwave-assisted rock-breaking technology,as a novel hybrid approach,is anticipated to facilitate the efficient excavation of complex rock formations.It is therefore crucial to understand the damage and failure mechanisms of rocks that have been subjected to irradiation.In this study,uniaxial compression experiments were conducted on granite specimens after 1.4 kW microwave irradiation for varying durations.Furthermore,a numerical method was proposed to solve electromagnetic-thermal-mechanical coupling problems by integrating finite and discrete elements.The results demonstrated a differential temperature distribution(high temperature in the middle and low-temperature areas at the ends)in the granite specimens under microwave irradiation,which resulted in a notable reduction in their physical and mechanical properties.As the duration of irradiation increased,the rate of heating and the extent of strength reduction both diminished,while the morphology and distribution of cracks at ultimate failure became increasingly complex.The numerical method effectively addresses the simulation challenges associated with the electromagnetic selective heating of granite containing multiple polar minerals under microwave irradiation.This approach accounted for the non-uniform thermal expansion of the minerals and provided a comprehensive model of damage progression under compression.
基金Project(10964004)supported by the National Natural Science Foundation of ChinaProject(20070231001)supported by Research Fund for the Doctoral Program of Higher Education of China+1 种基金Project(096RJZA104)supported by the Natural Science Foundation of Gansu Province,ChinaProject(SB14200801)supported by the Doctoral Fund of Lanzhou University of Technology
文摘A accelerated arithmetic algorithm of the dynamic computing regions was designed,and 3-dimensional numerical simulation of isothermal solidification for a binary alloy was implemented.The dendritic growth and the recalescence of Ni-Cu binary alloy during the solidification at different cooling rates were investigated.The effects of cooling rate on dendritic patterns and microsegregation patterns were studied.The computed results indicate that,with the increment of the cooling rate,the dendritic growth velocity increases,both the main branch and side-branches become slender,the secondary dendrite arm spacing becomes smaller,the inadequate solute diffusion in solid aggravates,and the severity of microsegregation ahead of interface aggravates.At a higher cooling rate,the binary alloy presents recalescence;while the cooling rate is small,no recalescence occurs.
基金the China Natural Science Fund(No.52171253)the Natural Science Foundation of Sichuan(No.2022NSFSCO949).
文摘Accurate 3-dimensional(3-D)reconstruction technology for nondestructive testing based on digital radiography(DR)is of great importance for alleviating the drawbacks of the existing computed tomography(CT)-based method.The commonly used Monte Carlo simulation method ensures well-performing imaging results for DR.However,for 3-D reconstruction,it is limited by its high time consumption.To solve this problem,this study proposes a parallel computing method to accelerate Monte Carlo simulation for projection images with a parallel interface and a specific DR application.The images are utilized for 3-D reconstruction of the test model.We verify the accuracy of parallel computing for DR and evaluate the performance of two parallel computing modes-multithreaded applications(G4-MT)and message-passing interfaces(G4-MPI)-by assessing parallel speedup and efficiency.This study explores the scalability of the hybrid G4-MPI and G4-MT modes.The results show that the two parallel computing modes can significantly reduce the Monte Carlo simulation time because the parallel speedup increment of Monte Carlo simulations can be considered linear growth,and the parallel efficiency is maintained at a high level.The hybrid mode has strong scalability,as the overall run time of the 180 simulations using 320 threads is 15.35 h with 10 billion particles emitted,and the parallel speedup can be up to 151.36.The 3-D reconstruction of the model is achieved based on the filtered back projection(FBP)algorithm using 180 projection images obtained with the hybrid G4-MPI and G4-MT.The quality of the reconstructed sliced images is satisfactory because the images can reflect the internal structure of the test model.This method is applied to a complex model,and the quality of the reconstructed images is evaluated.
基金The project supported by the Natural Science Foundation of Zhejiang Province of China under Grant No. Y604036 and State Key Laboratory of 0il/Gas Reservoir Geology and Exploitation ＂PLN0402＂ The authors would like to thank Prof. Sen-Yue Lou for his help and discussion.
文摘The （3＋1）-dimensional Jimbo-Miwa （JM） equation is solved approximately by using the conformal invariant asymptotic expansion approach presented by Ruan. By solving the new （3＋1）-dimensional integrable models, which are conformal invariant and possess Painlevé property, the approximate solutions are obtained for the JM equation, containing not only one-soliton solutions but also periodic solutions and multi-soliton solutions. Some approximate solutions happen to be exact and some approximate solutions can become exact by choosing relations between the parameters properly.
基金The authors express their sincere thanks to the anonymous referees for their constructive suggestions and kind help.
文摘In this paper, the entangled mapping approach （EMA） is applied to obtain variable separation solutions of （1＋1）-dimensional and （3＋1）-dimensional systems. By analysis, we firstly find that there also exists a common formula to describe suitable physical fields or potentials for these （1＋1）-dimensional models such as coupled integrable dispersionless （CID） and shallow water wave equations. Moreover, we find that the variable separation solution of the （3＋1）-dimensional Burgers system satisfies the completely same form as the universal quantity U1 in （2＋1）-dimensional systems. The only difference is that the function q is a solution of a constraint equation and p is an arbitrary function of three independent variables.
基金supported by the Program for NIM-Basic Research Business Expenses Key Field Program,China(No.AKYCX2315).
文摘The rapid identification of γ-emitting radionuclides with low activity levels in public areas is crucial for nuclear safety.However,classical methods rely on full-energy peaks in the integral spectrum,requiring sufficient count accumulation for evaluation,thereby limiting response time.The sequential Bayesian approach,which utilizes prior information and considers both photon energies and interarrival times,can significantly enhance the performance of radionuclides identification.This study proposes a theoretical optimization method for the traditional sequential Bayesian approach.Each photon is processed sequentially,and the corresponding posterior probability is updated in real time using a noninformative prior from the Bayesian theory.By comparing the posterior probabilities of the background and radionuclides based on the energy variance and time interval,the type of γ-rays can be identified(background characteristic γ-rays,Compton plateaus γ-rays,or radionuclide-specific characteristic γ-rays).By integrating the information from these multiple characteristic γ-rays,the presence and type of radionuclides were determined based on the final decision function and a set threshold.Based on theoretical research,verification experiments were conducted using a LaBr_(3)(Ce)detector in both low-and natural background radiation environments with typical radionuclides(^(137)Cs,^(60)Co,and ^(133)Ba).The results show that this approach can identify ^(137)Cs in 7.9 s and 8.5 s(source dose rate contribution:approximately 6.5×10^(−3)μGy/h),^(60)Co in 8.1 s and 9.8 s(approximately 4.8×10^(−2)μGy/h),and ^(133)Ba in 4.05 s and 5.99 s(approximately 3.4×10^(−2)μGy/h)under low and natural background radiation,respectively,with a miss rate below 0.01%.This demonstrates the effectiveness of the proposed approach for fast radionuclides identification,even at low activity levels and highlights its potential for enhancing public safety in diverse radiation environments.
