A generalized form of the error function, Gp(x)=pΓ(1/p)∫0xe−tpdt, which is directly associated with the gamma function, is evaluated for arbitrary real values of p>1and 0x≤+∞by employing a fast-converging power...A generalized form of the error function, Gp(x)=pΓ(1/p)∫0xe−tpdt, which is directly associated with the gamma function, is evaluated for arbitrary real values of p>1and 0x≤+∞by employing a fast-converging power series expansion developed in resolving the so-called Grandi’s paradox. Comparisons with accurate tabulated values for well-known cases such as the error function are presented using the expansions truncated at various orders.展开更多
Nickel-based cathodes in aqueous nickel-zinc batteries typically suffer from sluggish reaction kinetics and limited energy density.In situ introduction of metal phosphides and rational construction of heterostructures...Nickel-based cathodes in aqueous nickel-zinc batteries typically suffer from sluggish reaction kinetics and limited energy density.In situ introduction of metal phosphides and rational construction of heterostructures can effectively promote electron/ion transport.However,the complex evolution of phosphidation and intractable phosphidizing degree greatly affect the composition of active phase,active sites,charge transfer rate,and ion adsorption strength of cathodes.Herein,the critical bimetallic phosphide layer(CBPL)is constructed on the NiCo-layered double hydroxide(NiCo-LDH)skeleton by a controllable anion-exchange strategy,yielding a novel nanohybrid cathode(NiCo-P1.0,1.0 representing the mass ratio of Na_(2)H_(2)PO_(2)to NiCo-LDH).The high-conductivity CBPL with the inner NiCo-LDH forms extensive heterostructures,effectively regulating the electronic structure via charge transfer,thereby improving electrical conductivity.Remarkably,the CBPL exhibits unexpected electrochemical activity and synergizes with NiCo-LDH for electrode reactions,ultimately delivering extra energy.Benefiting from the bifunctional CBPL,NiCo-P1.0 delivers an optimal capacity of 286.64 mAh g^(−1)at 1C(1C=289 mAh g^(−1))and superb rate performance(a capacity retention of 72.22%at 40C).The assembled NiCo-P1.0//Zn battery achieves ultrahigh energy/power density(503.62 Wh kg^(−1)/18.62 kW kg^(−1),based on the mass loading of active material on the cathode),and the flexible quasi-solid-state pouch cell validates its practicality.This work demonstrates the superiority of bifunctional CBPL for surface modification,providing an effective and scalable compositing strategy in achieving high-performance cathodes for aqueous batteries.展开更多
A novel method based on zoom fast Fourier transform（FFT） is proposed for minimizing the burden processing of cross-ambiguity functions without affecting performance. The low-pass anti-aliasing filter in zoom FFT is ...A novel method based on zoom fast Fourier transform（FFT） is proposed for minimizing the burden processing of cross-ambiguity functions without affecting performance. The low-pass anti-aliasing filter in zoom FFT is realized by using the multistage filtering technique and the weighting processing is employed in the first stage filter to get rid of the redundancy of the computation. In practical systems, the input data is divided into overlapped data frames to avoid loss of detection ability which results in the rapid increase of computational complexity. A segment technique is also proposed in which CAF calculation of overlapped data frames is viewed as slide window FFT to decrease the computational complexity. The experimental results show that compared to the conventional methods, the proposed method can lower computational complexity and is consistent with the real time implementation in existing high-speed digital processors.展开更多
Infrared small target detection is a common task in infrared image processing.Under limited computa⁃tional resources.Traditional methods for infrared small target detection face a trade-off between the detection rate ...Infrared small target detection is a common task in infrared image processing.Under limited computa⁃tional resources.Traditional methods for infrared small target detection face a trade-off between the detection rate and the accuracy.A fast infrared small target detection method tailored for resource-constrained conditions is pro⁃posed for the YOLOv5s model.This method introduces an additional small target detection head and replaces the original Intersection over Union(IoU)metric with Normalized Wasserstein Distance(NWD),while considering both the detection accuracy and the detection speed of infrared small targets.Experimental results demonstrate that the proposed algorithm achieves a maximum effective detection speed of 95 FPS on a 15 W TPU,while reach⁃ing a maximum effective detection accuracy of 91.9 AP@0.5,effectively improving the efficiency of infrared small target detection under resource-constrained conditions.展开更多
An improved Reduced-Order Model(ROM)is proposed based on a flow-solution preprocessing operation and a fast sampling strategy to efficiently and accurately predict ionized hypersonic flows.This ROM is generated in low...An improved Reduced-Order Model(ROM)is proposed based on a flow-solution preprocessing operation and a fast sampling strategy to efficiently and accurately predict ionized hypersonic flows.This ROM is generated in low-dimensional space by performing the Proper Orthogonal Decomposition(POD)on snapshots and is coupled with the Radial Basis Function(RBF)to achieve fast prediction speed.However,due to the disparate scales in the ionized flow field,the conventional ROM usually generates spurious negative errors.Here,this issue is addressed by performing flow-solution preprocessing in logarithmic space to improve the conventional ROM.Then,extra orthogonal polynomials are introduced in the RBF interpolation to achieve additional improvement of the prediction accuracy.In addition,to construct high-efficiency snapshots,a trajectory-constrained adaptive sampling strategy based on convex hull optimization is developed.To evaluate the performance of the proposed fast prediction method,two hypersonic vehicles with classic configurations,i.e.a wave-rider and a reentry capsule,are used to validate the proposed method.Both two cases show that the proposed fast prediction method has high accuracy near the vehicle surface and the free-stream region where the flow field is smooth.Compared with the conventional ROM prediction,the prediction results are significantly improved by the proposed method around the discontinuities,e.g.the shock wave and the ionized layer.As a result,the proposed fast prediction method reduces the error of the conventional ROM by at least 45%,with a speedup of approximately 2.0×105compared to the Computational Fluid Dynamic(CFD)simulations.These test cases demonstrate that the method developed here is efficient and accurate for predicting ionized hypersonic flows.展开更多
针对观测器估计精度偏低及高速列车系统的强耦合、受外界扰动、参数时变等问题,提出一种基于补偿函数观测器的分数阶非奇异快速终端滑模控制算法(Compensating Function Observer-Fractional Order Non-singular Fast Terminal Sliding ...针对观测器估计精度偏低及高速列车系统的强耦合、受外界扰动、参数时变等问题,提出一种基于补偿函数观测器的分数阶非奇异快速终端滑模控制算法(Compensating Function Observer-Fractional Order Non-singular Fast Terminal Sliding Mode Control,CFO-FONFTSMC),以提高高速列车速度控制的鲁棒性和控制精度.首先,建立高速列车纵向多质点动力学模型,设计高精度的补偿函数观测器对系统的总扰动进行实时估计并补偿;然后,设计一种带状态负指数控制律的分数阶非奇异快速终端滑模控制算法,用于对列车的运行曲线进行跟踪控制,并通过李雅普诺夫稳定性理论证明系统在有限时间内的收敛性;最后,以CRH3型高速列车参数和合肥站-蚌埠南站的实际线路为实例,分别跟踪理想运行曲线和节能优化运行曲线进行实验验证.仿真结果表明:所提算法跟踪理想运行速度曲线的平均误差为0.01377 km/h,跟踪带干扰的节能优化运行速度曲线的平均误差为0.0364 km/h,相较于基于扩张状态观测器的滑模和非奇异快速终端滑模控制方法,所提方法具有最小的跟踪误差和更高的跟踪精度,验证了其有效性和可行性,可为列车速度跟踪控制领域的研究提供参考.展开更多
通过大涡模拟(Large Eddy Simulation,LES)湍流求解方法和概率密度函数输运方程(Transported Probability Density Function,TPDF)湍流燃烧求解方法结合,对煤油燃料双旋流燃烧室(Gas Turbine Model Combustor,GTMC)进行了模拟,并利用经...通过大涡模拟(Large Eddy Simulation,LES)湍流求解方法和概率密度函数输运方程(Transported Probability Density Function,TPDF)湍流燃烧求解方法结合,对煤油燃料双旋流燃烧室(Gas Turbine Model Combustor,GTMC)进行了模拟,并利用经验模态分解(Empirical Mode Decomposition,EMD)和快速傅里叶变换(Fast Fourier Transform,FFT)等方法分析了GTMC的温度和速度非定常特性,获得了脉动主频的空间分布。结果显示:空间坐标为(2 cm,0 cm,3 cm)的特征点的温度主频为47和761 Hz;对本征模态函数(Intrinsic Mode Function,IMF)进行显著性分析,能量密度最高的IMF的主频即原始数据的主频;温度脉动主要受湍流流动影响;根据瑞利数场,热-压力激发与抑制区域总是交替出现。展开更多
通过产品的FAST(Function Analysis System Technique)法分析,对现代家庭多功能组合车体进行合理的分析与应用。首先,根据用户需求和现有自行车的功能,采用FAST法创建自行车的功能树;然后,从功能树中选定目标功能的可能范围,确定功能需...通过产品的FAST(Function Analysis System Technique)法分析,对现代家庭多功能组合车体进行合理的分析与应用。首先,根据用户需求和现有自行车的功能,采用FAST法创建自行车的功能树;然后,从功能树中选定目标功能的可能范围,确定功能需求与工程度量;最后,基于目标功能设计了一款功能组合式自行车,并对其进行系统的人机关系和机械结构分析。基于以上创新设计过程,得出结论,印证FAST法在设计中的有效性和合理性,并阐述家庭多功能组合式车体的前景与创新展望。展开更多
文摘A generalized form of the error function, Gp(x)=pΓ(1/p)∫0xe−tpdt, which is directly associated with the gamma function, is evaluated for arbitrary real values of p>1and 0x≤+∞by employing a fast-converging power series expansion developed in resolving the so-called Grandi’s paradox. Comparisons with accurate tabulated values for well-known cases such as the error function are presented using the expansions truncated at various orders.
基金supported by the National Natural Science Foundation of China(No.52373249,W2433146)the Science and Technology Project of Yibin Sanjiang New Area(No.2023SJXQSXZJ003)the Fundamental Research Funds for the Central Universities(No.20822041F4045).
文摘Nickel-based cathodes in aqueous nickel-zinc batteries typically suffer from sluggish reaction kinetics and limited energy density.In situ introduction of metal phosphides and rational construction of heterostructures can effectively promote electron/ion transport.However,the complex evolution of phosphidation and intractable phosphidizing degree greatly affect the composition of active phase,active sites,charge transfer rate,and ion adsorption strength of cathodes.Herein,the critical bimetallic phosphide layer(CBPL)is constructed on the NiCo-layered double hydroxide(NiCo-LDH)skeleton by a controllable anion-exchange strategy,yielding a novel nanohybrid cathode(NiCo-P1.0,1.0 representing the mass ratio of Na_(2)H_(2)PO_(2)to NiCo-LDH).The high-conductivity CBPL with the inner NiCo-LDH forms extensive heterostructures,effectively regulating the electronic structure via charge transfer,thereby improving electrical conductivity.Remarkably,the CBPL exhibits unexpected electrochemical activity and synergizes with NiCo-LDH for electrode reactions,ultimately delivering extra energy.Benefiting from the bifunctional CBPL,NiCo-P1.0 delivers an optimal capacity of 286.64 mAh g^(−1)at 1C(1C=289 mAh g^(−1))and superb rate performance(a capacity retention of 72.22%at 40C).The assembled NiCo-P1.0//Zn battery achieves ultrahigh energy/power density(503.62 Wh kg^(−1)/18.62 kW kg^(−1),based on the mass loading of active material on the cathode),and the flexible quasi-solid-state pouch cell validates its practicality.This work demonstrates the superiority of bifunctional CBPL for surface modification,providing an effective and scalable compositing strategy in achieving high-performance cathodes for aqueous batteries.
基金Sponsored by the Excellent Young Scholar Research Fund of Beijing Institute of Technology (000Y01-5)BIT(UBF 200501F4208.4)
文摘A novel method based on zoom fast Fourier transform（FFT） is proposed for minimizing the burden processing of cross-ambiguity functions without affecting performance. The low-pass anti-aliasing filter in zoom FFT is realized by using the multistage filtering technique and the weighting processing is employed in the first stage filter to get rid of the redundancy of the computation. In practical systems, the input data is divided into overlapped data frames to avoid loss of detection ability which results in the rapid increase of computational complexity. A segment technique is also proposed in which CAF calculation of overlapped data frames is viewed as slide window FFT to decrease the computational complexity. The experimental results show that compared to the conventional methods, the proposed method can lower computational complexity and is consistent with the real time implementation in existing high-speed digital processors.
文摘Infrared small target detection is a common task in infrared image processing.Under limited computa⁃tional resources.Traditional methods for infrared small target detection face a trade-off between the detection rate and the accuracy.A fast infrared small target detection method tailored for resource-constrained conditions is pro⁃posed for the YOLOv5s model.This method introduces an additional small target detection head and replaces the original Intersection over Union(IoU)metric with Normalized Wasserstein Distance(NWD),while considering both the detection accuracy and the detection speed of infrared small targets.Experimental results demonstrate that the proposed algorithm achieves a maximum effective detection speed of 95 FPS on a 15 W TPU,while reach⁃ing a maximum effective detection accuracy of 91.9 AP@0.5,effectively improving the efficiency of infrared small target detection under resource-constrained conditions.
基金supported by the National Natural Science Foundation of China(Nos.11902271 and 91952203)the Fundamental Research Funds for the Central Universities of China(No.G2019KY05102)111 project on“Aircraft Complex Flows and the Control”of China(No.B17037)。
文摘An improved Reduced-Order Model(ROM)is proposed based on a flow-solution preprocessing operation and a fast sampling strategy to efficiently and accurately predict ionized hypersonic flows.This ROM is generated in low-dimensional space by performing the Proper Orthogonal Decomposition(POD)on snapshots and is coupled with the Radial Basis Function(RBF)to achieve fast prediction speed.However,due to the disparate scales in the ionized flow field,the conventional ROM usually generates spurious negative errors.Here,this issue is addressed by performing flow-solution preprocessing in logarithmic space to improve the conventional ROM.Then,extra orthogonal polynomials are introduced in the RBF interpolation to achieve additional improvement of the prediction accuracy.In addition,to construct high-efficiency snapshots,a trajectory-constrained adaptive sampling strategy based on convex hull optimization is developed.To evaluate the performance of the proposed fast prediction method,two hypersonic vehicles with classic configurations,i.e.a wave-rider and a reentry capsule,are used to validate the proposed method.Both two cases show that the proposed fast prediction method has high accuracy near the vehicle surface and the free-stream region where the flow field is smooth.Compared with the conventional ROM prediction,the prediction results are significantly improved by the proposed method around the discontinuities,e.g.the shock wave and the ionized layer.As a result,the proposed fast prediction method reduces the error of the conventional ROM by at least 45%,with a speedup of approximately 2.0×105compared to the Computational Fluid Dynamic(CFD)simulations.These test cases demonstrate that the method developed here is efficient and accurate for predicting ionized hypersonic flows.
文摘针对观测器估计精度偏低及高速列车系统的强耦合、受外界扰动、参数时变等问题,提出一种基于补偿函数观测器的分数阶非奇异快速终端滑模控制算法(Compensating Function Observer-Fractional Order Non-singular Fast Terminal Sliding Mode Control,CFO-FONFTSMC),以提高高速列车速度控制的鲁棒性和控制精度.首先,建立高速列车纵向多质点动力学模型,设计高精度的补偿函数观测器对系统的总扰动进行实时估计并补偿;然后,设计一种带状态负指数控制律的分数阶非奇异快速终端滑模控制算法,用于对列车的运行曲线进行跟踪控制,并通过李雅普诺夫稳定性理论证明系统在有限时间内的收敛性;最后,以CRH3型高速列车参数和合肥站-蚌埠南站的实际线路为实例,分别跟踪理想运行曲线和节能优化运行曲线进行实验验证.仿真结果表明:所提算法跟踪理想运行速度曲线的平均误差为0.01377 km/h,跟踪带干扰的节能优化运行速度曲线的平均误差为0.0364 km/h,相较于基于扩张状态观测器的滑模和非奇异快速终端滑模控制方法,所提方法具有最小的跟踪误差和更高的跟踪精度,验证了其有效性和可行性,可为列车速度跟踪控制领域的研究提供参考.
文摘通过产品的FAST(Function Analysis System Technique)法分析,对现代家庭多功能组合车体进行合理的分析与应用。首先,根据用户需求和现有自行车的功能,采用FAST法创建自行车的功能树;然后,从功能树中选定目标功能的可能范围,确定功能需求与工程度量;最后,基于目标功能设计了一款功能组合式自行车,并对其进行系统的人机关系和机械结构分析。基于以上创新设计过程,得出结论,印证FAST法在设计中的有效性和合理性,并阐述家庭多功能组合式车体的前景与创新展望。
