检索结果-南通市图书馆

Online estimation and characteristic analysis of double nugget diameters during aluminum/steel resistance spot welding process

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2024年第8期31卷 2053-2067页

作者： Kang Zhou Wen-xiao Yu Bao-kai Ren Gang Wang school of Mechatronical Engineering Beijing Institute of TechnologyBeijing 100081China

Online estimation of the double nugget diameters was performed by means of a back propagation neural *** double nugget diameters were obtained using actual welding experiment and numerical simulation,according to different characteristics of aluminum nugget and steel *** input of the neural network was some key characteristic parameters extracted from dynamic power signal,which were peak point,knee point and their variation rate over time,as well as heat energy delivered into the welding *** architecture of the neural network was confirmed by confirming the number of neurons in hidden layer through a series of *** key parameters of the neural network were obtained by means of training 81 arrays of data ***,the neural network was used to test the remaining 20 arrays of verifying data set,and the results showed that both of the mean errors for the two nugget diameters were below 3%.In addition,corresponding analyses showed that the accuracy of two nugget diameters was higher than that of tensile-shear strength.

关键词： Resistance spot welding Aluminum Steel Double nugget Dynamic power signal.Neural network

Conceptual design and configurations selection of S/H-UAVs based on Q-rung dual hesitant double layer FQFD

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第9期37卷 193-205页

作者： Dun YANG Li LIU Wencan BAI Weiyong TIAN school of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China

For the conceptual design phase of Unmanned Aerial Vehicles(UAVs),a process for conceptual design and configuration selection of Solar/Hydrogen powered UAVs(S/H-UAVs)is *** design requirements of S/H-UAVs were analyzed *** proposed process used Fuzzy Quality Function Deployment(FQFD)to establish logical and quantitative ***,in order to appropriately describe the hesitancy of experts while making decision,it used Q-Rung Dual Hesitant Fuzzy Sets(QRDHFS)to score the *** addition,a decision-making framework is proposed to perform a logical selection of typical layouts based on defuzzi-fication method and Technique for Order Preference by Similarity to the Ideal Solution(TOPSIS).The present process has been applied for S/*** resulting set of design requirements con-sists of three categories:Mission Requirements(MRs),Engineering Characteristics(ECs)and Tech-nical Indicators(TIs).Four typical layouts of S/H-UAVs were sorted and *** performance of four typical layouts were evaluated and the Strut-Braced Wing(SBW)with external hydrogen storage was selected as the best layout for S/H-UAVs.

关键词： Hybrid powered UAV Conceptual design Q-Rung Dual Hesitant Fuzzy Set(QRDHFS) Quality function deployment Strut-braced wing

Influence of ambient temperature on the CO_(2)emitted of light-duty vehicle

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2024年第6期140卷 59-68页

作者： Dan Tan Yachao Wang Jianwei Tan Jiachen Li Changyu Wang Yunshan Ge school of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China

Because of global warming,people have paid more attention to greenhouse gas emitted by *** quantify the impact of temperature on vehicle CO_(2)emissions,this study was conducted using the world light vehicle test cycle on two light-duty E10 gasoline vehicles a ambient temperatures of-10,0,23,and 40℃,and found that CO_(2)emission factors of Vehicle1 in the low-speed phase were 22.07%and 20.22%higher than those of Vehicle 2 at cold star and hot start under-10℃.The reason was vehicle 1 had a larger displacement and more friction pairs than vehicle *** was the highest CO_(2)emission at the low-speed phase due to low average speed,frequent acceleration,and *** CO_(2)temperature factor and the ambient temperature had a strong linear correlation(R2=0.99).According to CO_(2)temperature factors and their relationships,CO_(2)emission factors of other ambien temperatures could be calculated when the CO_(2)emission factor of 23℃was obtained,and the method also could be used to obtain the CO_(2)temperature factors of different *** separate the effect of load setting and temperature variation on CO_(2)emission quantitatively a method was *** results showed that the load setting was dominant for the CO_(2)emission *** with 23℃,the CO_(2)emission for vehicle 1 caused by load setting variation were 62.83 and 47.42 g/km,respectively at-10 and 0℃,while those fo vehicle 2 were 45.01 and 35.63 g/km,respectively.

关键词： CO_(2)emission Ambient temperature E10 gasoline Light-duty vehicle WLTC

A novel predictive braking energy recovery strategy for electric vehicles considering motor thermal protection

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2024年第4期67卷 1253-1269页

作者： YANG Chao SUN TongLin YANG LiuQuan ZHANG YuHang WANG WeiDa school of Mechanical Engineering Beijing Institute of TechnologyBeijing 100084China

Braking energy recovery(BER)aims to recover the vehicle's kinetic energy by coordinating the motor and mechanical braking torque to extend the driving range of the electric vehicle(EV).To achieve this goal,the motor/generator mode requires frequent switching and prolonged operation during *** this case,the motor temperature will unavoidably rise,potentially triggering motor thermal protection(MTP).Activating MTP increases the risk of motor component failure,and the EV typically disables the BER ***,maximizing BER while reducing the risk of motor overheating is a challenging *** address this issue,this article proposes a predictive BER strategy with MTP using the non-smooth Pontryagin Minimum Principle(NSPMP)for ***,a Markov long short-term memory(MLSTM)model is designed to obtain future velocity ***,the BER problem with MTP in the studied EV is embedded in a model predictive control(MPC)***,under the MPC framework,the NSPMP strategy is proposed to resolve the problem of ***,the performance of the proposed strategy is verified through simulation and a hardware-in-loop *** results show that in two real-world driving cycles,compared to the rule-based strategy,the proposed strategy reduced power consumption by 1.24%and0.96%,respectively,and effectively limited motor ***,under global cycle conditions,this strategy demonstrated better MTP control performance compared to other benchmark strategies.

关键词： electric vehicle braking energy recovery strategy motor thermal protection non-smooth PMP

Scattering-based hybrid network for facial attribute classification

在线全文

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2024年第3期18卷 105-116页

作者： Na LIU Fan ZHANG Liang CHANG Fuqing DUAN school of Artificial Intelligence Beijing Normal UniversityBeijing 100875China

Face attribute classification(FAC)is a high-profile problem in biometric verification and face *** recent research has been devoted to extracting more delicate image attribute features and exploiting the inter-attribute correlations,significant challenges still *** scattering transform(WST)is a promising non-learned feature *** has been shown to yield more discriminative representations and outperforms the learned representations in certain *** to the image classification task,WST can enhance subtle image texture information and create local deformation *** paper designs a scattering-based hybrid block,to incorporate frequency-domain(WST)and image-domain features in a channel attention manner(Squeezeand-Excitation,SE),termed WS-SE *** with CNN,WS-SE achieves a more efficient FAC performance and compensates for the model sensitivity of the small-scale affine *** addition,to further exploit the relationships among the attribute labels,we propose a learning strategy from a causal *** cause attributes defined using the causalityrelated information can be utilized to infer the effect attributes with a high confidence *** analysis experiments demonstrate the effectiveness of our model,and our hybrid model obtains state-of-the-art results in two public datasets.

关键词： wavelet scattering transform causality-related learning facial attribute classification

Full lifetime demonstration of a Micro-Cathode-Arc thruster evolution characteristics

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第6期37卷 38-49页

作者： Zhe ZHANG Zijing ZHAO Xiangyang LIU Ningfei WANG school of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China

Ground lifetime test is the most crucial experiment to assess the performance,*** flight qualification of electric propulsion,and it can bring new insights for understanding the operation *** work demonstrates a full lifetime test of 140000 cycles on a Micro-Cathode-Arc Thruster(μCAT)with 160μs charging time and 86 mJ charging energy.A four-probe resistivity measurement method is utilized to investigate variations in the conductive film thickness and resistivity throughout the thruster *** film parameters show that the lifetime of theμCAT can be divided into three *** the initial stage,the film thickness decreases by 1.2μm and the resistivity increases significantly due to the high discharge intensity and intense film ablation;In the steady stage,the change of the film thickness is within 5%,and the resistivity of the film increases slowly from 0.050Ω·mm to 0.223Ω·*** the end stage,the resistivity exponentially increases from 0.223Ω·mm to 1.176Ω·mm,with the increase accounting for 81%,ultimately resulting in the failure of the thruster open ***,the evolution of discharge parameters,and the variation of plume parameters are measured throughout the *** discharge characteristics also show significant differences in the duration of voltage and current in these three *** results of plume shape and plasma parameters are also well con-sistent with the discharge parameters and film *** results suggest that,for evaluating the steady stage lifetime of thrusters,the film thickness is the best indicator compared to the variations in resistivity and voltage-current *** the end stage,the plasma plume *** duration,and plume parameters can conveniently and clearly characterize the thruster failures and irregularity.

关键词： Electric propulsion Lifetime test Micro-Cathode-Arc Thruster(uCAT) Conductive film Discharge characteristics Plasma parameters

Floquet spectrum and universal dynamics of a periodically driven two-atom system

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2024年第2期33卷 436-443页

作者：谢文柱周正强李轩崔思淼孙明远 school of Science Beijing University of Posts and TelecommunicationsBeijing 100876China

We investigate the Floquet spectrum and excitation properties of a two-ultracold-atom system with periodically driven interaction in a three-dimensional harmonic *** interaction between the atoms is changed by varying the s-wave scattering length in two ways,the cosine and the square-wave *** is found that as the driving frequency increases,the Floquet spectrum exhibits two main features for both modulations,the accumulating and the spreading of the quasienergy levels,which further lead to different dynamical *** accumulation is associated with collective excitations and the persistent growth of the energy,while the spread indicates that the energy is bounded at all *** initial scattering length,the driving frequency and amplitude can all significantly change the Floquet spectrum as well as the ***,the corresponding relation between them is valid ***,we propose a mechanism for selectively exciting the system to one specific state by using the avoided crossing of two quasienergy levels,which could guide preparation of a desired state in experiments.

关键词： Floquet spectrum universal dynamics two-atom system avoided crossing

Research on aiming methods for small sample size shooting tests of two-dimensional trajectory correction fuse

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2024年第3期33卷 506-517页

作者： Chen Liang Qiang Shen Zilong Deng Hongyun Li Wenyang Pu Lingyun Tian Ziyang Lin school of Mechatronical Engineering Beijing Institute of TechnologyBeijing 100081China

The longitudinal dispersion of the projectile in shooting tests of two-dimensional trajectory corrections fused with fixed canards is extremely large that it sometimes exceeds the correction ability of the correction fuse *** impact point easily deviates from the target,and thus the correction result cannot be readily ***,the cost of shooting tests is considerably high to conduct many tests for data *** address this issue,this study proposes an aiming method for shooting tests based on small sample *** proposed method uses the Bootstrap method to expand the test data;repeatedly iterates and corrects the position of the simulated theoretical impact points through an improved compatibility test method;and dynamically adjusts the weight of the prior distribution of simulation results based on Kullback-Leibler divergence,which to some extent avoids the real data being"submerged"by the simulation data and achieves the fusion Bayesian estimation of the dispersion *** experimental results show that when the simulation accuracy is sufficiently high,the proposed method yields a smaller mean-square deviation in estimating the dispersion center and higher shooting accuracy than those of the three comparison methods,which is more conducive to reflecting the effect of the control algorithm and facilitating test personnel to iterate their proposed structures and algorithms.;in addition,this study provides a knowledge base for further comprehensive studies in the future.

关键词： Two-dimensional trajectory correction fuse Small sample size test Compatibility test KL divergence Fusion bayesian estimation

Two-stage Planning Method for Energy Router Considering Its Optimal Operation in Distribution Networks

在线全文

学校读者我要写书评

暂无评论

CSEE Journal of Power and Energy Systems 2024年第2期10卷 605-616页

作者： Meifu Chen Mingchao Xia Qifang Chen school of Electrical Engineering Beijing Jiaotong UniversityBeijing 100044China

An energy router can effectively optimize the network loss and power quality of distribution networks. The optimal configuration of the energy router is relatively complex because issues dynamically influence each other, such as the location of the energy router, optimal number and capacity of its ports, and building new distribution lines for the ports. Presently, there has been very few research studies on the practical problems for the energy router. In this paper, a planning model of an energy router combined with the distribution network is established, which fully exploits the active and reactive power control abilities of the energy router to optimize the operation of the grid. The configuration problem is decoupled into two stages. The upper layer determines the location of the energy router and the parameters of the candidate new distribution lines for the ports. The lower layer calculates the optimal configuration of the energy router by minimizing the total annual cost. Because of the same rated bus voltage in the distribution network, the existing structure of the energy router is changed to be more applicable for the distribution network, and then the power flow model of the energy router is also modified. Due to the nonlinearity of the model, the planning model is converted into a mixed-integer second-order cone model to solve efficiently. In addition, some core factors influencing the optimal scheme of the energy router are also analyzed in this paper. Simulation results show that the optimal scheme of the energy router can significantly improve the economic deployment of the energy router, and optimize the network loss and power quality of the distribution network.

关键词： Capacity allocation distribution network energy router optimal operation