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Programmable structured surfaces can change the future of wireless communications

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Light(Science & Applications) 2022年第7期11卷 1341-1342页

作者： lei xu Mohsen Rahmani Advanced Optics and Photonics Laboratory Department of EngineeringSchool of Science and TechnologyNottingham Trent UniversityNottingham NG118NSUK

An innovative time-varying metasurface has been reported to realise dual-channel data transmissions for light-to-microwave signal *** a novel technique is a remarkable step forward to realise full-spectrum networks for catering for the growing demand for wireless ***,this technique enriches the functionalities of tunable metasurfaces and stimulates new information-oriented applications.

关键词： wireless tunable surfaces

Underactuated spacecraft angular velocity stabilization and three-axis attitude stabilization using two single gimbal control moment gyros

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Acta Mechanica Sinica 2010年第2期26卷 279-288页

作者： lei Jin Shijie xu Department of Guidance Navigation and Control School of Astronautics Beihang University 100191 Beijing China

Angular velocity stabilization control and attitude stabilization control for an underactuated spacecraft using only two single gimbal control moment gyros （SGCMGs） as actuators is investigated. First of all, the dynamic model of the underactuated spacecraft is established and the singularity of different configurations with the two SGCMGs is analyzed. Under the assumption that the gimbal axes of the two SGCMGs are installed in any direction, and that the total system angular momentum is not zero, a state feedback control law via Lyapunov method is designed to globally asymptotically stabilize the angular velocity of spacecraft. Under the assumption that the gimbal axes of the two SGCMGs are coaxially installed along anyone of the three principal axes of spacecraft inertia, and that the total system angular momentum is zero, a discontinuous state feedback control law is designed to stabilize three-axis attitude of spacecraft with respect to the inertial frame. Furthermore, the singularity escape of SGCMGs for the above two control problems is also studied. Simulation results demonstrate the validity of the control laws.

关键词： Single gimbal control moment gyro ·Undcractuated spacecraft · Angular velocity stabilization · Three-axis attitude stabilization·Singularity

Leakage performance of labyrinth seal for oil sealing of aero-engine

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Propulsion and Power Research 2019年第1期8卷 13-22页

作者： Guoqing Li qian Zhang Zhijun lei Enliang Huang Hongwei Wu Gang xu Institute of Engineering Thermophysics.Chinese Academy of Sciences.Beijing 100190 China University of Chinese Academy of Sciences.Beijing 100190 China Research Institute of Petroleum Exploration and Development Beijing 100083China School of Engineering and Technology University of Hertfordshire.Hatfield AL109AB.United Kingdom

Experimental investigation has been done to evaluate the leakage performance of labyrinth seal for oil sealing on high-speed sealing test rig at different working and geometric *** values of pressure ratio ranging from 1.0 to 2.0 were used and the rotating speed varied from 0 to 30,000 *** Taylor number was invited to response the effect of *** was injected at the rate from 1.2 L/min to 2.8 L/min to check the sealing *** was measured at different seal configurations including sealing clearance,tooth tip thickness,pitch,teeth number,front inclined angle and oil-throwing *** from gas sealing,the application of oil-throwing tooth in oil sealing attracted much interest as an obvious alternative to the conventional labyrinth seal.A blocking ring was captured during testing,which establishes understanding of underlying flow mechanisms in the clearance and plays an important role in oil *** is a critical Taylor number at which the leakage coefficient drops *** the critical Taylor number,a parabola rule *** optimal composition of tooth tip thickness,teeth number,oil-throwing angle and front inclined angle exists where the leakage performance behaves better.

关键词： Labyrinth seal Leakage Rotating Oil sealing Aero-engine

DCVAE-adv:A Universal Adversarial Example Generation Method for White and Black Box Attacks

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Tsinghua Science and Technology 2024年第2期29卷 430-446页

作者： lei xu Junhai Zhai College of Mathematics and Information Science Hebei UniversityBaoding 071002China

Deep neural network(DNN)has strong representation learning ability,but it is vulnerable and easy to be fooled by adversarial *** order to handle the vulnerability of DNN,many methods have been *** general idea of existing methods is to reduce the chance of DNN models being fooled by observing some designed adversarial examples,which are generated by adding perturbations to the original *** this paper,we propose a novel adversarial example generation method,called *** from the existing methods,DCVAE-adv constructs adversarial examples by mixing both explicit and implicit perturbations without using original ***,the proposed method can be applied to both white box and black box *** addition,in the inference stage,the adversarial examples can be generated without loading the original images into memory,which greatly reduces the memory *** compared DCVAE-adv with three most advanced adversarial attack algorithms:FGSM,AdvGAN,and AdvGAN++.The experimental results demonstrate that DCVAE-adv is superior to these state-of-the-art methods in terms of attack success rate and transfer ability for targeted *** code is available at https://***/xzforeverlove/DCVAE-adv.

关键词： deep neural network adversarial examples white box attack black box attack robustness

FAST: Its Scientific Achievements and Prospects

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The Innovation 2020年第3期1卷 44-49页

作者： lei qian Rui Yao Jinghai Sun Jinlong xu Zhichen Pan Peng Jiang National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

FAST is the largest single-dish radio telescope in the *** characteristics of FAST are presented and analyzed in the context of the parameter space to show how FAST science achievements are *** summarize the scientific achievements of FAST and discuss its future science based on the new parts of the parameter space that can be explored by FAST.

关键词： RADIO TELESCOPE RADIO ASTRONOMY

Design of a Flexible Bionic Ankle Prosthesis Based on Subject-specific Modeling of the Human Musculoskeletal System

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Journal of Bionic Engineering 2023年第3期20卷 1008-1020页

作者： Jianqiao Jin Kunyang Wang lei Ren Zhihui qian Wei Liang Xiaohan xu Shun Zhao xuewei Lu Di Zhao xu Wang Luquan Ren Key Laboratory of Bionic Engineering Ministry of EducationJilin UniversityChangchun130025China Weihai Institute for Bionics Jilin UniversityWeihai264402China School of Mechanical Aerospace and Civil EngineeringUniversity of ManchesterManchesterM139PLUK

A variety of prosthetic ankles have been successfully developed to reproduce the locomotor ability for lower limb amputees in daily lives. However, they have not been shown to sufficiently improve the natural gait mechanics commonly observed in comparison to the able-bodied, perhaps due to over-simplified designs of functional musculoskeletal structures in prostheses. In this study, a flexible bionic ankle prosthesis with joints covered by soft material inclusions is developed on the basis of the human musculoskeletal system. First, the healthy side ankle–foot bones of a below-knee amputee were reconstructed by CT imaging. Three types of polyurethane rubber material configurations were then designed to mimic the soft tissues around the human ankle, providing stability and flexibility. Finite element simulations were conducted to determine the proper design of the rubber materials, evaluate the ankle stiffness under different external conditions, and calculate the rotation axes of the ankle during walking. The results showed that the bionic ankle had variable stiffness properties and could adapt to various road surfaces. It also had rotation axes similar to that of the human ankle, thus restoring the function of the talocrural and subtalar joints. The inclination and deviation angles of the talocrural axis, 86.2° and 75.1°, respectively, as well as the angles of the subtalar axis, 40.1° and 29.9°, were consistent with the literature. Finally, dynamic characteristics were investigated by gait measurements on the same subject, and the flexible bionic ankle prosthesis demonstrated natural gait mechanics during walking in terms of ankle angles and moments.

关键词： Ankle prosthesis Bionic design Soft materials Variable stiffness Gait mechanics

Focused evaluation of the roles of macrophages in chimeric antigen receptor (CAR) T cell therapy associated cytokine release syndrome

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Cancer Biology & Medicine 2022年第3期19卷 333-342页

作者： Hanfei Guo lei qian Jiuwei Cui Cancer Center the First Hospital of Jilin UniversityChangchun 130021China

Cytokine release syndrome(CRS)is a major obstacle to the widespread clinical application of chimeric antigen receptor(CAR)T cell *** can also be induced by infections(such as SARS-CoV-2),drugs(such as therapeutic antibodies),and some autoimmune ***-derived macrophages play key roles in the pathogenesis of CRS,and participate in the production and release of the core CRS cytokines,including interleukin(IL)-1,IL-6,and interferon-γ.In this review,we summarize the roles of macrophages in CRS and discuss new developments in macrophage activation and the related mechanisms of cytokine regulation in CRS.

关键词： Chimeric antigen receptor CAR T cells cytokine release syndrome macrophage

On dynamic analysis method for large-scale train-track-substructure interaction

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Railway Engineering Science 2022年第2期30卷 162-182页

作者： lei xu School of Civil Engineering Central South UniversityChangsha 410075China National Engineering Laboratory for High-Speed Railway Construction Changsha 410075China

Train–track–substructure dynamic interaction is an extension of the vehicle–track coupled *** contributes to evaluate dynamic interaction and performance between train–track system and its *** the first time,this work devotes to presenting engineering practical methods for modeling and solving such large-scale train–track–substructure interaction systems from a unified *** this study,a train consists of several multi-rigid-body vehicles,and the track is modeled by various finite *** track length needs only satisfy the length of a train plus boundary length at two sides,despite how long the train moves on the *** substructures and their interaction matrices to the upper track are established as independent modules,with no need for additionally building the track structures above substructures,and accordingly saving computational ***–substructure local coordinates are defined to assist the confirming of the overlapped portions between the train–track system and the substructural system to effectively combine the cyclic calculation and iterative solution *** advancement of this model lies in its convenience,efficiency and accuracy in continuously considering the vibration participation of multi-types of substructures against the moving of a train on the *** examples have shown the effectiveness of this method;besides,influence of substructures on train–track dynamic behaviors is illustrated accompanied by clarifying excitation difference of different track irregularity spectrums.

关键词： Train Track dynamic interaction Railway substructures Finite elements Dynamics system Iterative solution Tunnel Bridge

Microstructural evolution and properties of a Cu-Cr-Ag alloy during continuous manufacturing process

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Rare Metals 2021年第8期40卷 2213-2220页

作者： Gao-lei xu Li-Jun Peng Guo-Jie Huang Hao-Feng Xie Zhen Yang xue Feng Xiang-qian Yin xu-Jun Mi State Key Laboratory of Nonferrous Metals and Processes GRIMAT Engineering Institute Co.Ltd.Beijing101417China Zhejiang Libo Industrial Co. Ltd.Shaoxing312050China

Microstructure evolution and properties of a Cu-Cr-Ag alloy during the continuous manufacturing process were investigated in detail by scanning electron microscopy(SEM)and transmission electron microscopy(TEM)in the *** Cu-Cr-Ag alloy rod with uniform compositions is fabricated by upward continuous casting *** of the Cr phases are observed in the ascast *** the continuous extrusion process,the severe shear deformation and the dynamic aging *** average grain size of as-extruded alloy is much smaller than that of as-cast *** fcc and bcc Cr precipitates appear in the *** interaction mode between dislocations and precipitates can be identified as Orowan bypass mode according to the TEM *** overall difference in the yield strength between as-cast and as-extruded Cu-Cr-Ag alloy is attributed to solid solution strengthening,grain refinement strengthening,precipitation hardening and working hardening.

关键词： Cu-Cr-Ag alloy Upward continuous casting Continuous extrusion Microstructure Physical properties