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Synchrotron X-ray diffraction characterization of phase transformations during thermomechanical processing of a Ti38Nb alloy

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Rare Metals 2021年第11期40卷 3269-3278页

作者： qing-Kun meng Huan Li Chong-Hang zhao Wen Ma Fu-Xiang Wei Yan-Wei Sui Ji-qiu qi School of Materials Science and Physics China University of Mining and TechnologyXuzhou 221116China Department of Materials Science and Chemical Engineering Stony Brook UniversityStony BrookNY 11794USA Grinm Group Co. Ltd.Beijing 100088China

The phase transformations during thermomechanical processing can be employed to optimize mechanical properties of β-type Ti ***,such understandings are still lacking for the alloy consisting of dual β+α" phases in solution-treated and quenched *** this paper,the phase transformations in a Ti38 Nb model alloy subjected to different thermomechanical processing were investigated by using synchrotron X-ray diffraction(SXRD) experiments,and their influence on the Young’s modulus was *** results indicated that highdensity dislocations introduced by cold rolling still existed after annealing at temperatures lower than 573 K,which can decrease the martensitic transformation start temperature to below room *** annealing temperatures increasing,the α"→β,β→ω_(iso),and β→α phase transformations occurred *** annealing temperature of 473 K,the specimen consisted of a trace of α"and ω phases as well as dominant β phase which was kept to room temperature by the high density of dislocations,rather than by the chemical *** a result,an ultralow Young’s modulus of 25.9 GPa was *** investigation not only provides in-depth understandings of the phase transformations during thermomechanical processing of β-type Ti alloys,but also sheds light on designing biomedical Ti alloys with ultralow Young’s modulus.

关键词： Ti alloys Phase transformation Thermomechanical processing Synchrotron X-ray diffraction

Premature deposition of lithium polysulfide in lithium-sulfur batteries

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Journal of Energy Chemistry 2023年第7期82卷 507-512,I0011页

作者： Zi-Xian Chen Yu-Tong Zhang Chen-Xi Bi meng zhao Rui Zhang Bo-Quan Li Jia-qi Huang School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Advanced Research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China

Lithium-sulfur(Li-S)batteries have attracted extensive attention due to ultrahigh theoretical energy density of 2600 Wh kg^(-1).Liquid-solid deposition from dissolved lithium polysulfides(LiPSs)to solid lithium sulfide(Li_(2)S)largely determines the actual battery ***,a premature liquidsolid deposition process of LiPSs is revealed at higher thermodynamic potential than Li_(2)S deposition in Li-S *** premature solid deposit exhibits higher chemical state and hemispherical morphology in comparison with Li_(2)S,and the premature deposition process is slower in kinetics and higher in deposition ***,a supersaturation deposition mechanism is proposed to rationalize the above findings based on thermodynamic *** work demonstrates a unique premature liquid-solid deposition process of Li-S batteries.

关键词： Lithium-sulfur batteries Lithium polysulfides Liquid-solid deposition Supersaturation

Evaluation on a 400 Wh kg^(-1)lithium-sulfur pouch cell

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Journal of Energy Chemistry 2022年第3期31卷 24-29,I0002页

作者： Ge Ye meng zhao Li-Peng Hou Wei-Jing Chen Xue-qiang Zhang Bo-Quan Li Jia-qi Huang School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Advanced Research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical EngineeringTsinghua UniversityBeijing 100084China Beijing Key Laboratory of Lignocellulosic Chemistry Beijing Forestry UniversityBeijing 100083China

Lithium–sulfur(Li–S)batteries are highly regarded as next-generation energy storage devices due to their ultrahigh theoretical energy density of 2600 Wh kg^(−1).However,practical high-energy-density Li–S pouch cells suffer from limited cycling lifespan with rapid loss of active ***,systematic evaluation on a 400 Wh kg^(−1)Li–S pouch cell is carried out to reveal the working and failure mechanism of Li–S batteries under practical *** morphology,spatial distribution and species analysis of sulfur,and capacity retention of electrodes are respectively evaluated after the first cycle of discharge or *** lithium polysulfides are found in electrolyte even at the end of discharge or charge,where the sulfur redox reactions are reversible with high capacity ***,severe morphology change is identified on lithium metal anode,yet there remains substantial active lithium to support the following *** work not only demonstrates unique behaviors of Li–S batteries under practical conditions,which is essential for promoting the progress of Li–S pouch cells,but also affords a systematic evaluation methodology to guide further investigation on high-energy-density Li–S batteries.

关键词： Lithium-sulfur batteries Pouch cell High energy density Failure analysis

Adaptive leader–follower formation control for swarms of unmanned aerial vehicles with motion constraints and unknown disturbances

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Chinese Journal of Aeronautics 2020年第11期33卷 2972-2988页

作者： Yueqian LIANG qi DONG Yanjie zhao China Academy of Electronics and Information Technology Beijing 100041China

In this paper,the 3D leader–follower formation control problem,which focuses on swarms of fixed-wing Unmanned Aerial Vehicles(UAVs)with motion constraints and disturbances,has been *** formation errors of the follower UAVs have been transformed into the Frenet-Serret *** control laws satisfying five motion constraints(i.e.,linear velocity,linear acceleration,heading rate,climb rate and climb angle)have been *** convergence of the control laws has been discussed via the Lyapunov stability *** addition,to address the unknown disturbances,an adaptive disturbance observer is ***,formation control laws involving estimated disturbances are presented as *** collision avoidance between UAVs is achieved with the artificial potential *** results obtained using four scenarios verify the effectiveness of the proposed method in situations with constant disturbances and varying disturbances,as well as without disturbances.

关键词： Constraint handling Disturbance rejection Formation flying Leader–follower method Swarm

Derivative Estima tes of It era ted Spherical Average and Ext ension

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Acta Mathematica Sinica,English Series 2021年第7期37卷 1109-1130页

作者： meng WANG Jun Yan zhao Department of Mathematics Zhejiang UniversityHangzhou 310027P.R.China Department of Mathematics Zhejiang Normal UniversityJinhua 321004P.R.China

In the paper,we study derivative estimates of the iterated spherical averages(At)^(N)(f).We obtain the optimal range of exponents(α,N,p)to ensure the L^(p)boundedness of P(■/■x)(A1)^(N)(f)for 1≤p≤∞,where P is a homogeneous polynomial of degree *** main theorem extends some known *** an application,we obtain the smallest N such that(A1)^(N):L^(p)(R^(n))→L_(α)^(p)(R^(n)).

关键词： H^(p)space spherical mean Bessel function H^(p)multiplier wave operator

Cross-modal learning using privileged information for long-tailed image classification

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Computational Visual Media 2024年第5期10卷 981-992页

作者： Xiangxian Li Yuze Zheng Haokai Ma Zhuang qi Xiangxu meng Lei meng School of Software Shandong UniversityJinan 250101China

The prevalence of long-tailed distributions in real-world data often results in classification models favoring the dominant classes,neglecting the less frequent *** approaches address the issues in long-tailed image classification by rebalancing data,optimizing weights,and augmenting ***,these methods often struggle to balance the performance between dominant and minority classes because of inadequate representation learning of the *** address these problems,we introduce descriptional words into images as cross-modal privileged information and propose a cross-modal enhanced method for long-tailed image classification,referred to as *** improves the learning of intraclass similarity of tail-class representations by cross-modal alignment and captures the difference between the head and tail classes in semantic space by cross-modal *** fusing the above information,CMLTNet achieved an overall performance that was better than those of benchmark long-tailed and cross-modal learning methods on the long-tailed cross-modal datasets,NUS-WIDE and *** effectiveness of the proposed modules was further studied through ablation *** a case study of feature distribution,the proposed model was better in learning representations of tail classes,and in the experiments on model attention,CMLTNet has the potential to help learn some rare concepts in the tail class through mapping to the semantic space.

关键词： long-tailed classification cross-modal learning representation learning privileged infor-mation

Tracking the maneuvering spacecraft propelled by swing propulsion of constant magnitude

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Journal of Systems Engineering and Electronics 2020年第2期31卷 370-382页

作者： ZHAI Guang WANG Yanxin zhao qi School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China Systems Engineering Research Institute Beijing 100094China

This paper proposes partially norm-preserving filtering for a class of spacecraft in the presence of time-varying, but constant-magnitude maneuver. The augmented state Kalman filter(ASKF) is commonly used to track the maneuvering spacecraft with unknown constant propulsion;however, if the maneuver varies via time, the estimation performance will be degraded. To promote the tracking performance of the ASKF in case of time-invariant,constant-magnitude disturbance, the partially norm-preserving ASKF is developed by applying the norm constraint on the unknown maneuver. The proposed estimator, which is decomposed into two partial estimators and iteratively propagated in turns,projects the unconstrained maneuver estimation onto the Euclidian surface spanned by the norm constraint. The illustrative numerical example is provided to show the efficiency of the proposed method.

关键词： maneuvering spacecraft tracking augmented state norm-preserving Kalman filter

Integration of GPS and low cost INS for pedestrian navigation aided by building layout

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Chinese Journal of Aeronautics 2013年第5期26卷 1283-1289页

作者： Feng Wenquan zhao Hongbo zhao qi Li Jingwen School of Electronics and Information Engineering Beihang University

In outdoor environments, GPS is often used for pedestrian navigation by utilizing its signals for position computation, but in indoor or semi-obstructed environments, GPS signals are often unavailable. Therefore, pedestrian navigation for these environments should be realized by the integration of GPS and inertial navigation system （INS）. However, the lowcost INS could induce errors that may result in a large position drift. The problem can be minimized by mounting the sensors on the pedestrian＇s foot, using zero velocity update （ZUPT） method with the standard navigation algorithm to restrict the error growth. However, heading drift still remains despite using ZUPT measurements since the heading error is unobservable. Also, tbot mounted INS suffers from the initialization ambiguity of position and heading from GPS. In this paper, a novel algorithm is developed to mitigate the heading drift problem when using ZUPT. The method uses building lay- out to aid the heading measurement in Kalman filter, and it could also be combined for the initial- ization. The algorithm has been investigated with real field trials using the low cost Microstrain 3DM-GX3-25 inertial sensor, a Leica GS10 GPS receiver and a uBlox EVK-6T GPS receiver. It could be concluded that the proposed method offers a significant improvement in position accuracy for the long period, allowing pedestrian navigation for nearly40 min with mean position error less than 2.8 m. This method also has a considerable effect on the accuracy of the initialization.

关键词： Heading drift Initialization Integrated navigation Pedestrian navigation Satellite navigation Zero velocity update

Analysis of detection capabilities of LEO reconnaissance satellite constellation based on coverage performance

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Journal of Systems Engineering and Electronics 2018年第1期29卷 98-104页

作者： meng Shaofei SHU Jiansheng YANG qi XIA Wei Graduate School Rocket Force University of Engineering

In the design problem of low earth orbit(LEO) reconnaissance satellite constellation, optimization of coverage performance is the design goal in most current methods. However,in the using process, the user only concerns with the detection capabilities rather than coverage performance. To establish the relationship between these two aspects, the reconnaissance processes of normal stochastic targets are considered and the mathematic models of detection processes are built. The indicators of coverage performance are used to evaluate the detection probability and expectation of detection time delay, which are important factors in reconnaissance constellation estimation viewed from military intelligence discipline. The conclusions confirmed by the final simulation will be useful in LEO reconnaissance constellation design, optimization and evaluation.

关键词： low earth orbit(LEO) reconnaissance satellite constellation detection capability Monte Carlo experiment