Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycle...Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.展开更多
The complex vibration directly affects the dynamic safety of drill string in ultra-deep wells and extra-deep wells.It is important to understand the dynamic characteristics of drill string to ensure the safety of dril...The complex vibration directly affects the dynamic safety of drill string in ultra-deep wells and extra-deep wells.It is important to understand the dynamic characteristics of drill string to ensure the safety of drill string.Due to the super slenderness ratio of drill string,strong nonlinearity implied in dynamic analysis and the complex load environment,dynamic simulation of drill string faces great challenges.At present,many simulation methods have been developed to analyze drill string dynamics,and node iteration method is one of them.The node iteration method has a unique advantage in dealing with the contact characteristics between drill string and borehole wall,but its drawback is that the calculation consumes a considerable amount of time.This paper presents a dynamic simulation method of drilling string in extra-deep well based on successive over-relaxation node iterative method(SOR node iteration method).Through theoretical analysis and numerical examples,the correctness and validity of this method were verified,and the dynamics characteristics of drill string in extra-deep wells were calculated and analyzed.The results demonstrate that,in contrast to the conventional node iteration method,the SOR node iteration method can increase the computational efficiency by 48.2%while achieving comparable results.And the whirl trajectory of the extra-deep well drill string is extremely complicated,the maximum rotational speed downhole is approximately twice the rotational speed on the ground.The dynamic torque increases rapidly at the position of the bottom stabilizer,and the lateral vibration in the middle and lower parts of drill string is relatively intense.展开更多
In this paper,a distributed adaptive dynamic programming(ADP)framework based on value iteration is proposed for multi-player differential games.In the game setting,players have no access to the information of others&#...In this paper,a distributed adaptive dynamic programming(ADP)framework based on value iteration is proposed for multi-player differential games.In the game setting,players have no access to the information of others'system parameters or control laws.Each player adopts an on-policy value iteration algorithm as the basic learning framework.To deal with the incomplete information structure,players collect a period of system trajectory data to compensate for the lack of information.The policy updating step is implemented by a nonlinear optimization problem aiming to search for the proximal admissible policy.Theoretical analysis shows that by adopting proximal policy searching rules,the approximated policies can converge to a neighborhood of equilibrium policies.The efficacy of our method is illustrated by three examples,which also demonstrate that the proposed method can accelerate the learning process compared with the centralized learning framework.展开更多
In this paper, we propose a two-grid algorithm for solving the stream function formulation of the stationary Navies-Stokes equations. The algorithm is constructed by reducing the original system to one small, nonlinea...In this paper, we propose a two-grid algorithm for solving the stream function formulation of the stationary Navies-Stokes equations. The algorithm is constructed by reducing the original system to one small, nonlinear system on the coarse mesh space and two similar linear systems （with same stiffness matrix but different right-hand side） on the fine mesh space. The convergence analysis and error estimation of the algorithm are given for the case of conforming elements. Furthermore, the Mgorithm produces a numerical solution with the optimal asymptotic H^2-error. Finally, we give a numerical illustration to demonstrate the effectiveness of the two-grid algorithm for solving the Navier-Stokes equations.展开更多
In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to ...In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to obtain the maximal positive definite solution of nonlinear matrix equation X+A^(*)X|^(-α)A=Q with the case 0<α≤1.Based on this method,a new iterative algorithm is developed,and its convergence proof is given.Finally,two numerical examples are provided to show the effectiveness of the proposed method.展开更多
Modified Chebyshev Picard Iteration is an iterative numerical method for solving linear or non-linear ordinary differential equations.In a serial computational environment the method has been shown to compete with,or ...Modified Chebyshev Picard Iteration is an iterative numerical method for solving linear or non-linear ordinary differential equations.In a serial computational environment the method has been shown to compete with,or outperform,current state of practice numerical integrators.This paper presents several improvements to the basic method,designed to further increase the computational efficiency of solving the equations of perturbed orbit propagation.展开更多
This paper consists of two parts. In the first part, we discuss the Hoelder continuity of Cauchy-type integral operator T of isotonic functions and the relationship between ｜｜T[f] ｜｜α and ｜｜f｜｜α. In the seco...This paper consists of two parts. In the first part, we discuss the Hoelder continuity of Cauchy-type integral operator T of isotonic functions and the relationship between ｜｜T[f] ｜｜α and ｜｜f｜｜α. In the second part, firstly, we introduce a modified Cauchy-type integral operator T＇ and demonstrate that the operator T＇ has a unique fixed point by the Contraction Mapping Principle. Then we give the Mann iterative sequence and prove that the Mann iterative sequence strongly converges to the fixed point of the modified Cauchy-type integral operator T＇.展开更多
Due to the digital transformation tendency among cultural institutions and the substantial influence of the social media platform,the demands of visual communication keep increasing for promoting traditional cultural ...Due to the digital transformation tendency among cultural institutions and the substantial influence of the social media platform,the demands of visual communication keep increasing for promoting traditional cultural artifacts online.As an effective medium,posters serve to attract public attention and facilitate broader engagement with cultural artifacts.However,existing poster generation methods mainly rely on fixed templates and manual design,which limits their scalability and adaptability to the diverse visual and semantic features of the artifacts.Therefore,we propose CAPGen,an automated aesthetic Cultural Artifacts Poster Generation framework built on a Multimodal Large Language Model(MLLM)with integrated iterative optimization.During our research,we collaborated with designers to define principles of graphic design for cultural artifact posters,to guide the MLLM in generating layout parameters.Later,we generated these parameters into posters.Finally,we refined the posters using an MLLM integrated with a multi-round iterative optimization mechanism.Qualitative results show that CAPGen consistently outperforms baseline methods in both visual quality and aesthetic performance.Furthermore,ablation studies indicate that the prompt,iterative optimization mechanism,and design principles significantly enhance the effectiveness of poster generation.展开更多
In seismic prospecting, fi eld conditions and other factors hamper the recording of the complete seismic wavefi eld; thus, data interpolation is critical in seismic data processing. Especially, in complex conditions, ...In seismic prospecting, fi eld conditions and other factors hamper the recording of the complete seismic wavefi eld; thus, data interpolation is critical in seismic data processing. Especially, in complex conditions, prestack missing data affect the subsequent highprecision data processing workfl ow. Compressive sensing is an effective strategy for seismic data interpolation by optimally representing the complex seismic wavefi eld and using fast and accurate iterative algorithms. The seislet transform is a sparse multiscale transform well suited for representing the seismic wavefield, as it can effectively compress seismic events. Furthermore, the Bregman iterative algorithm is an efficient algorithm for sparse representation in compressive sensing. Seismic data interpolation methods can be developed by combining seismic dynamic prediction, image transform, and compressive sensing. In this study, we link seismic data interpolation and constrained optimization. We selected the OC-seislet sparse transform to represent complex wavefields and used the Bregman iteration method to solve the hybrid norm inverse problem under the compressed sensing framework. In addition, we used an H-curve method to choose the threshold parameter in the Bregman iteration method. Thus, we achieved fast and accurate reconstruction of the seismic wavefi eld. Model and fi eld data tests demonstrate that the Bregman iteration method based on the H-curve norm in the sparse transform domain can effectively reconstruct missing complex wavefi eld data.展开更多
在车辆高速剧烈运动场景下,现有激光雷达-惯性里程计(LiDAR-inertial odometry,LIO)因IMU前向传播误差的快速累积,导致车辆的运动畸变补偿精度下降,进而引发"补偿误差-配准误差-状态估计误差"的级联效应,最终造成车辆定位轨...在车辆高速剧烈运动场景下,现有激光雷达-惯性里程计(LiDAR-inertial odometry,LIO)因IMU前向传播误差的快速累积,导致车辆的运动畸变补偿精度下降,进而引发"补偿误差-配准误差-状态估计误差"的级联效应,最终造成车辆定位轨迹显著偏离真实状态,本文提出了基于迭代误差卡尔曼滤波(iterated error-state Kalman filter,IESKF)的自适应激光雷达-惯性里程计(state-adaptive update LiDAR-inertial odometry,SAU-LIO)。首先,提出基于协方差特征值阈值的动态调整策略,以实时监测LIO误差累积趋势,自适应缩短状态更新时间间隔,有效抑制剧烈运动下的误差发散;其次,结合线特征与面特征的联合提取策略,构建概率观测模型,通过观测协方差矩阵约束实现不同置信度特征的最优加权融合,实现环境特征的有效利用。最后,基于NCLT(the university of Michigan north campus long-term vision and LIDAR dataset)、UTBM(EU long-term dataset with multiple sensors for autonomous driving)标准数据集及实车试验平台的验证结果表明:SAU-LIO算法在保证实时性的前提下,与对比算法相比具有更高的定位精度,在低速工况下,平均定位误差较次优的对比算法减小14.3%,在组合工况下,平均定位误差较次优的对比算法减小9.4%。展开更多
在雷达目标跟踪领域,当目标与雷达传感器存在相对运动时,多普勒(Doppler)效应致使接收信号产生频率偏移。这种频率变化与目标距离测量存在耦合关系,即多普勒距离耦合问题。在相控阵雷达采用线性调频(Linear Frequency Modulation,LFM)...在雷达目标跟踪领域,当目标与雷达传感器存在相对运动时,多普勒(Doppler)效应致使接收信号产生频率偏移。这种频率变化与目标距离测量存在耦合关系,即多普勒距离耦合问题。在相控阵雷达采用线性调频(Linear Frequency Modulation,LFM)信号进行常规跟踪时,虽然能获取大时宽带宽积提升距离分辨率,但脉冲压缩后产生的强距离多普勒耦合效应使传统的距离速度测量算法出现收敛速度慢、精度低的问题,尤其在航迹起始阶段对高速目标的跟踪极为不利,严重影响了雷达系统对目标的实时、精准监测。提出一种多普勒距离耦合下的三帧快速收敛算法。该算法利用3帧具有不同耦合系数的波形,构建多元约束方程,通过联合解算实现多目标速度和位置参数的同步获取。在验证处理流程中,采用迭代优化机制,对测量结果进行动态校准,有效降低距离与速度参数间的相互干扰,逐步逼近最优的距离和速度测量结果,从而实现快速、精准的目标跟踪。通过理论分析、蒙特卡罗仿真和外场实测数据验证,该三帧快速收敛算法展现出优异性能。在航迹起始阶段,对目标距离和速度测量解算的收敛速度是传统算法的4倍以上。所提出的多普勒距离耦合下的三帧快速收敛算法成功地解决了传统算法在处理多普勒距离耦合问题时存在的收敛慢、精度低等难题。该算法具有创新的波形设计和迭代优化策略,显著提升了相控阵雷达在复杂条件下的目标跟踪性能,为雷达目标跟踪技术的发展提供了新的思路和方法,具有较高的理论价值和实际应用前景。展开更多
基金Supported by National Key R&D Program of China(Grant No.2019YFE0121300)。
文摘Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.
基金supported by the National Natural Science Foundation of China(52174003,52374008).
文摘The complex vibration directly affects the dynamic safety of drill string in ultra-deep wells and extra-deep wells.It is important to understand the dynamic characteristics of drill string to ensure the safety of drill string.Due to the super slenderness ratio of drill string,strong nonlinearity implied in dynamic analysis and the complex load environment,dynamic simulation of drill string faces great challenges.At present,many simulation methods have been developed to analyze drill string dynamics,and node iteration method is one of them.The node iteration method has a unique advantage in dealing with the contact characteristics between drill string and borehole wall,but its drawback is that the calculation consumes a considerable amount of time.This paper presents a dynamic simulation method of drilling string in extra-deep well based on successive over-relaxation node iterative method(SOR node iteration method).Through theoretical analysis and numerical examples,the correctness and validity of this method were verified,and the dynamics characteristics of drill string in extra-deep wells were calculated and analyzed.The results demonstrate that,in contrast to the conventional node iteration method,the SOR node iteration method can increase the computational efficiency by 48.2%while achieving comparable results.And the whirl trajectory of the extra-deep well drill string is extremely complicated,the maximum rotational speed downhole is approximately twice the rotational speed on the ground.The dynamic torque increases rapidly at the position of the bottom stabilizer,and the lateral vibration in the middle and lower parts of drill string is relatively intense.
基金supported by the Aeronautical Science Foundation of China(20220001057001)an Open Project of the National Key Laboratory of Air-based Information Perception and Fusion(202437)
文摘In this paper,a distributed adaptive dynamic programming(ADP)framework based on value iteration is proposed for multi-player differential games.In the game setting,players have no access to the information of others'system parameters or control laws.Each player adopts an on-policy value iteration algorithm as the basic learning framework.To deal with the incomplete information structure,players collect a period of system trajectory data to compensate for the lack of information.The policy updating step is implemented by a nonlinear optimization problem aiming to search for the proximal admissible policy.Theoretical analysis shows that by adopting proximal policy searching rules,the approximated policies can converge to a neighborhood of equilibrium policies.The efficacy of our method is illustrated by three examples,which also demonstrate that the proposed method can accelerate the learning process compared with the centralized learning framework.
基金supported by National Foundation of Natural Science under the Grant 11071216
文摘In this paper, we propose a two-grid algorithm for solving the stream function formulation of the stationary Navies-Stokes equations. The algorithm is constructed by reducing the original system to one small, nonlinear system on the coarse mesh space and two similar linear systems （with same stiffness matrix but different right-hand side） on the fine mesh space. The convergence analysis and error estimation of the algorithm are given for the case of conforming elements. Furthermore, the Mgorithm produces a numerical solution with the optimal asymptotic H^2-error. Finally, we give a numerical illustration to demonstrate the effectiveness of the two-grid algorithm for solving the Navier-Stokes equations.
基金Supported in part by Natural Science Foundation of Guangxi(2023GXNSFAA026246)in part by the Central Government's Guide to Local Science and Technology Development Fund(GuikeZY23055044)in part by the National Natural Science Foundation of China(62363003)。
文摘In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to obtain the maximal positive definite solution of nonlinear matrix equation X+A^(*)X|^(-α)A=Q with the case 0<α≤1.Based on this method,a new iterative algorithm is developed,and its convergence proof is given.Finally,two numerical examples are provided to show the effectiveness of the proposed method.
文摘Modified Chebyshev Picard Iteration is an iterative numerical method for solving linear or non-linear ordinary differential equations.In a serial computational environment the method has been shown to compete with,or outperform,current state of practice numerical integrators.This paper presents several improvements to the basic method,designed to further increase the computational efficiency of solving the equations of perturbed orbit propagation.
基金Supported by the National Natural Science Foundation of China(Grant Nos.1077104911171349)the Science Foundation of Hebei Province(Grant No.A2010000346)
文摘This paper consists of two parts. In the first part, we discuss the Hoelder continuity of Cauchy-type integral operator T of isotonic functions and the relationship between ｜｜T[f] ｜｜α and ｜｜f｜｜α. In the second part, firstly, we introduce a modified Cauchy-type integral operator T＇ and demonstrate that the operator T＇ has a unique fixed point by the Contraction Mapping Principle. Then we give the Mann iterative sequence and prove that the Mann iterative sequence strongly converges to the fixed point of the modified Cauchy-type integral operator T＇.
基金supported by the National Key Research and Development Program of China(2023YFF0906502)the Postgraduate Research and Innovation Project of Hunan Province under Grant(CX20240473).
文摘Due to the digital transformation tendency among cultural institutions and the substantial influence of the social media platform,the demands of visual communication keep increasing for promoting traditional cultural artifacts online.As an effective medium,posters serve to attract public attention and facilitate broader engagement with cultural artifacts.However,existing poster generation methods mainly rely on fixed templates and manual design,which limits their scalability and adaptability to the diverse visual and semantic features of the artifacts.Therefore,we propose CAPGen,an automated aesthetic Cultural Artifacts Poster Generation framework built on a Multimodal Large Language Model(MLLM)with integrated iterative optimization.During our research,we collaborated with designers to define principles of graphic design for cultural artifact posters,to guide the MLLM in generating layout parameters.Later,we generated these parameters into posters.Finally,we refined the posters using an MLLM integrated with a multi-round iterative optimization mechanism.Qualitative results show that CAPGen consistently outperforms baseline methods in both visual quality and aesthetic performance.Furthermore,ablation studies indicate that the prompt,iterative optimization mechanism,and design principles significantly enhance the effectiveness of poster generation.
基金supported by the National Natural Science Foundation of China(Nos.41274119,41174080,and 41004041)the 863 Program of China(No.2012AA09A20103)
文摘In seismic prospecting, fi eld conditions and other factors hamper the recording of the complete seismic wavefi eld; thus, data interpolation is critical in seismic data processing. Especially, in complex conditions, prestack missing data affect the subsequent highprecision data processing workfl ow. Compressive sensing is an effective strategy for seismic data interpolation by optimally representing the complex seismic wavefi eld and using fast and accurate iterative algorithms. The seislet transform is a sparse multiscale transform well suited for representing the seismic wavefield, as it can effectively compress seismic events. Furthermore, the Bregman iterative algorithm is an efficient algorithm for sparse representation in compressive sensing. Seismic data interpolation methods can be developed by combining seismic dynamic prediction, image transform, and compressive sensing. In this study, we link seismic data interpolation and constrained optimization. We selected the OC-seislet sparse transform to represent complex wavefields and used the Bregman iteration method to solve the hybrid norm inverse problem under the compressed sensing framework. In addition, we used an H-curve method to choose the threshold parameter in the Bregman iteration method. Thus, we achieved fast and accurate reconstruction of the seismic wavefi eld. Model and fi eld data tests demonstrate that the Bregman iteration method based on the H-curve norm in the sparse transform domain can effectively reconstruct missing complex wavefi eld data.
文摘在车辆高速剧烈运动场景下,现有激光雷达-惯性里程计(LiDAR-inertial odometry,LIO)因IMU前向传播误差的快速累积,导致车辆的运动畸变补偿精度下降,进而引发"补偿误差-配准误差-状态估计误差"的级联效应,最终造成车辆定位轨迹显著偏离真实状态,本文提出了基于迭代误差卡尔曼滤波(iterated error-state Kalman filter,IESKF)的自适应激光雷达-惯性里程计(state-adaptive update LiDAR-inertial odometry,SAU-LIO)。首先,提出基于协方差特征值阈值的动态调整策略,以实时监测LIO误差累积趋势,自适应缩短状态更新时间间隔,有效抑制剧烈运动下的误差发散;其次,结合线特征与面特征的联合提取策略,构建概率观测模型,通过观测协方差矩阵约束实现不同置信度特征的最优加权融合,实现环境特征的有效利用。最后,基于NCLT(the university of Michigan north campus long-term vision and LIDAR dataset)、UTBM(EU long-term dataset with multiple sensors for autonomous driving)标准数据集及实车试验平台的验证结果表明:SAU-LIO算法在保证实时性的前提下,与对比算法相比具有更高的定位精度,在低速工况下,平均定位误差较次优的对比算法减小14.3%,在组合工况下,平均定位误差较次优的对比算法减小9.4%。
文摘在雷达目标跟踪领域,当目标与雷达传感器存在相对运动时,多普勒(Doppler)效应致使接收信号产生频率偏移。这种频率变化与目标距离测量存在耦合关系,即多普勒距离耦合问题。在相控阵雷达采用线性调频(Linear Frequency Modulation,LFM)信号进行常规跟踪时,虽然能获取大时宽带宽积提升距离分辨率,但脉冲压缩后产生的强距离多普勒耦合效应使传统的距离速度测量算法出现收敛速度慢、精度低的问题,尤其在航迹起始阶段对高速目标的跟踪极为不利,严重影响了雷达系统对目标的实时、精准监测。提出一种多普勒距离耦合下的三帧快速收敛算法。该算法利用3帧具有不同耦合系数的波形,构建多元约束方程,通过联合解算实现多目标速度和位置参数的同步获取。在验证处理流程中,采用迭代优化机制,对测量结果进行动态校准,有效降低距离与速度参数间的相互干扰,逐步逼近最优的距离和速度测量结果,从而实现快速、精准的目标跟踪。通过理论分析、蒙特卡罗仿真和外场实测数据验证,该三帧快速收敛算法展现出优异性能。在航迹起始阶段,对目标距离和速度测量解算的收敛速度是传统算法的4倍以上。所提出的多普勒距离耦合下的三帧快速收敛算法成功地解决了传统算法在处理多普勒距离耦合问题时存在的收敛慢、精度低等难题。该算法具有创新的波形设计和迭代优化策略,显著提升了相控阵雷达在复杂条件下的目标跟踪性能,为雷达目标跟踪技术的发展提供了新的思路和方法,具有较高的理论价值和实际应用前景。
