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Bimagnetic metal constructed core-shell structure of Fe@Co nanowires for multi-band microwave absorption

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Progress in Natural Science:Materials International 2024年第2期34卷 354-361页

作者： Ping-an Yang Rui cai Haibo Ruan Nanqing Zhang Xin Huang Rui Li Yuxin Zhang Yi Lu zhihao Zhou School of Automation Chongqing University of Posts and Telecommunications Chongqing Key Laboratory of Materials Surface & Interface Science Chongqing University of Arts and Sciences College of Engineering and Technology Zunyi Normal College College of Material Science and Engineering Chongqing University

Controlled fabrication of materials by surface modification techniques has been a hot research topic. In this paper,one-dimensional(1D) core-shell structure Fe@Co nanowires(NWs) were successfully prepared by anchoring 0-dimensional(0D) Co nanoparticles on 1D Fe NWs based on the in situ reduction method. The electromagnetic parameters of the specimens at a filler mass fraction of 25 wt% were tested and the microwave loss mechanism was deeply analyzed. Binary magnetic metals in a core-shell structure have excellent multi-band microwave absorption capability(S-band, X-band and Ku-band). This is due to the heterogeneous interface and magnetic coupling effects tuning the dielectric and magnetic loss. This study offers a workable plan for creating effective multi-band magnetic metal-based microwave absorbers.

关键词： Core-shell structure Interface Magnetic coupling Microwave absorption One-dimensional nanowires

Distributed coordinated control scheme of UAV swarm based on heterogeneous roles

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Chinese Journal of Aeronautics 2022年第1期35卷 81-97页

作者： Jiang ZHAO Jiaming SUN zhihao cai Yingxun WANG Kun WU School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100083China Flying College Beihang UniversityBeijing 100083China

This paper proposes a new distributed coordinated control scheme based on heterogeneous roles for Unmanned Aerial Vehicle(UAV)swarm to achieve formation control.First,the framework of the distributed coordinated control scheme is designed on the basis of Distributed Model Predictive Control(DMPC).Then,the effect of heterogeneous roles including leader,coordinator and follower is discussed,and the role-based cost functions are developed to improve the performance of coordinated control for UAV swarm.Furthermore,a group of coordination strategies are proposed for UAVs with different roles to achieve swarm conflict resolution.Numerical simulations demonstrate that the presented distributed coordinated control scheme is effective to formulate and maintain the desired formation for the UAV swarm.

关键词： Coordination strategy Distributed control Heterogeneous roles Swarm intelligence Unmanned Aerial Vehicles(UAV)

Natural variation of an autophagy-family gene among rice subspecies affects grain size and weight

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The Crop Journal 2024年第1期12卷 121-132页

作者： Shiying Huang Peng Wang caijing Li Qingwen Zhou Tao Huang Yicong cai Qin Cheng Hui Wang Qi Zhong zhihao Chen Liping Chen Haohua He Jianmin Bian Key Laboratory of Crop Physiology Ecology and Genetic BreedingMinistry of Education.Jiangxi Agricultural UniversityNanchang 330045JiangxiChina Weill Cornell Medical Immunology and Microbiology1300 York AvenueBox 62New YorkNY 10065USA

Elucidating the genetic basis of natural variation in grain size and weight among rice varieties can help breeders develop high-yielding varieties.We identified a novel gene,GW3a(Grain Weight 3a)(LOC_Os03g27350),that affects rice grain size and weight.gw3a mutants showed higher total starch content and dry matter accumulation than the wild type(WT),Nipponbare,suggesting that GW3a negatively regulates grain size and weight.Moreover,our study found that GW3a interacted with OsATG8 by cleaving it,suggesting that GW3a may be involved in the assembly of autophagosomes and starch degradation in plants.The haplotype analysis of GW3a showed functional differences between indica and japonica rice.Taken together,we conclude that GW3a is expressed in the autophagosome pathway regulating starch metabolism in rice,affecting yield-related traits,such as grain size,grain weight and thousand grain weight(TGW).Our findings also shed new light on autophagy-mediated yield trait regulation,proposing a possible strategy for the genetic improvement of high-yield germplasm in rice.

关键词： Grain size GW3a Autophagy Starch content

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对外担保与企业经营风险

中南财经政法大学学报 2024年第3期 29-42页

作者：邵志浩才国伟青岛大学经济学院山东青岛266061 中山大学岭南学院广东广州510275

基于中国资本市场违规担保不断“爆雷”以及企业外部环境不确定性增加的现实背景,本文以2008—2021年中国A股上市公司为研究样本,探讨对外担保对实体企业经营风险的影响及其作用机制。研究发现,企业对外提供担保显著提高了自身的经营风... 详细信息

基于中国资本市场违规担保不断“爆雷”以及企业外部环境不确定性增加的现实背景,本文以2008—2021年中国A股上市公司为研究样本,探讨对外担保对实体企业经营风险的影响及其作用机制。研究发现,企业对外提供担保显著提高了自身的经营风险水平。影响机制检验表明,对外担保主要通过强化融资约束、加剧大股东资金占用和高管在职消费行为以及降低经营能力来增加企业经营风险。异质性分析表明,对外担保对经营风险的提升作用在非国有企业、管理层持股比例低的企业、控股股东两权分离度高的企业以及所处产品市场竞争程度低的企业中更加明显。进一步研究发现,虽然对外担保有助于企业通过对方担保获取借贷资金,但这些资金可能没有用于企业生产经营活动,即对外担保不能为企业带来明显收益。并且,对外担保提高了企业退市概率,表明对外担保风险具有不可控性。

关键词：对外担保经营风险融资约束资源侵占经营能力

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多约束条件下四旋翼机动轨迹跟踪一体化控制方法

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北京航空航天大学学报 2024年第1期50卷 48-60页

作者：王英勋李欣蔡志浩赵江北京航空航天大学自动化科学与电气工程学院北京100191

四旋翼无人机高动态飞行需求的增加使其成为一个越来越热门的研究主题。针对四旋翼执行废墟裂缝和树林缝隙穿越任务时的大机动轨迹状态跟踪控制问题,提出基于模型预测控制的一体化控制方法,包含多约束条件下的高机动轨迹规划和多参考状... 详细信息

四旋翼无人机高动态飞行需求的增加使其成为一个越来越热门的研究主题。针对四旋翼执行废墟裂缝和树林缝隙穿越任务时的大机动轨迹状态跟踪控制问题,提出基于模型预测控制的一体化控制方法,包含多约束条件下的高机动轨迹规划和多参考状态量的一体化跟踪控制,并通过飞行试验验证了所提方法相比前馈PID控制方法在跟踪规划的高机动轨迹时的优越性能。在飞行试验中,四旋翼成功穿越了60°滚转角的窄框,其实际滚转角达到60°大角度的同时,z轴误差仅为0.065 m。

关键词：多约束一体化控制模型预测控制轨迹跟踪轨迹规划

Fast level-flight to hover mode transition and altitude control in tiltrotor’s landing operation

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Chinese Journal of Aeronautics 2021年第1期34卷 181-193页

作者： Ningjun LIU zhihao cai Yingxun WANG Jiang ZHAO Institute of Unmanned System Beihang UniversityBeijing 100083China School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100083China

An attempt is made to implement a faster level-flight to hover mode transition in tiltrotor’s landing process for the purpose of shortening its landing time. A three-stage tiltrotor landing maneuver is designed, and corresponding control modules and algorithms are created based on the analysis of the flight dynamics and the required actions of tiltrotor’s landing operation. As the altitude control is vital for tiltrotor’s near-ground landing, an Extended State Observer(ESO) control module of the Active Disturbance Rejection Control(ADRC) is designed to reduce altitude fluctuations in the fast mode transition, which makes the designed maneuver workable at very low altitudes. Simulations are conducted to verify the effectiveness of the designed maneuver and the validity of ESO control in various flight conditions. Flight test results that finally prove the effectiveness of the desired fast transition maneuver are reported.

关键词： Tiltrotor Transition Flight control VTOL UAV ADRC

Predictor-based model reference adaptive roll and yaw control of a quad-tiltrotor UAV

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Chinese Journal of Aeronautics 2020年第1期33卷 282-295页

作者： Ningjun LIU zhihao cai Jiang ZHAO Yingxun WANG School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100083China

An attempt is made to apply modern control technology to the roll and yaw control of a rudderless quad-tiltrotor Unmanned Aerial Vehicle(UAV)in the latter part of the flight mode transition,where aerodynamic forces on the tiltrotor’s wings start to take effect.A predictor-based adaptive roll and yaw controller is designed to compensate for system uncertainties and parameter changes.A dynamics model of the tiltrotor is built.A Radial-Basis Function(RBF)neural network and offline adaptation method are used to reduce flight controller workload and cope with the nonlinearities in the controls.Simulations are conducted to verify the reference model response tracking and yaw-roll control decoupling ability of the adaptive controller,as well as the validity of the offline adaptation method.Flight tests are conducted to confirm the ability of the adaptive controller to track different roll and yaw reference model responses.The decoupling of roll and yaw controls is also tested in flight via coordinated turn maneuvers with different rotor tilt angles.

关键词： Adaptive control Flight control Tiltrotor UAV VTOL

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基于动态视觉传感器的无人机目标检测与避障

北京航空航天大学学报 2024年第1期50卷 144-153页

作者：蔡志浩陈文军赵江王英勋北京航空航天大学自动化科学与电气工程学院北京100191

针对无人机在动态环境中感知动态目标与躲避高速动态障碍物,提出了基于动态视觉传感器的目标检测与避障算法。设计了滤波方法和运动补偿算法,滤除事件流中背景噪声、热点噪声及由相机自身运动产生的冗余事件;设计了一种融合事件图像和RG... 详细信息

针对无人机在动态环境中感知动态目标与躲避高速动态障碍物,提出了基于动态视觉传感器的目标检测与避障算法。设计了滤波方法和运动补偿算法,滤除事件流中背景噪声、热点噪声及由相机自身运动产生的冗余事件;设计了一种融合事件图像和RGB图像的动态目标融合检测算法,保证检测的可靠性。根据检测结果对目标运动轨迹进行估计,结合障碍物运动特点和无人机动力学约束改进速度障碍法躲避动态障碍物。大量仿真试验、手持试验及飞行试验验证了所提算法的可行性。

关键词：事件相机事件滤波运动补偿融合检测速度障碍法

Virtual target guidance-based distributed model predictive control for formation control of multiple UAVs

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Chinese Journal of Aeronautics 2020年第3期33卷 1037-1056页

作者： zhihao cai Longhong WANG Jiang ZHAO Kun WU Yingxun WANG School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100083China Flying College Beihang UniversityBeijing 100083China

The paper proposes a Virtual Target Guidance(VTG)-based distributed Model Predictive Control(MPC) scheme for formation control of multiple Unmanned Aerial Vehicles(UAVs).First, a framework of distributed MPC scheme is designed in which each UAV only shares the information with its neighbors, and the obtained local Finite-Horizon Optimal Control Problem(FHOCP) can be solved by swarm intelligent optimization algorithm.Then, a VTG approach is developed and integrated into the distributed MPC scheme to achieve trajectory tracking and obstacle avoidance.Further, an event-triggered mechanism is proposed to reduce the computational burden for UAV formation control, which takes into consideration the predictive state errors as well as the convergence of cost function.Numerical simulations show that the proposed VTG-based distributed MPC scheme is more computationally efficient to achieve formation control of multiple UAVs in comparison with the traditional distributed MPC method.

关键词： Distributed Model Predictive Control(MPC) Event-triggered mechanism Formation control Obstacle avoidance Unmanned Aerial Vehicles(UAVs) Virtual Target Guidance(VTG)