检索结果-南通市图书馆

Applied Mathematics and Mechanics(English Edition) 2018年第9期39卷 1239-1258页

作者： xudong zheng Runsen ZHANG Qi WANG School of Aeronautic Science and Engineering Beihang University

The objective of this study is to investigate the effects of the Coulomb dry friction model versus the modified Coulomb friction model on the dynamic behavior of the slider-crank mechanism with a revolute clearance joint. The normal and tangential forces acting on the contact points between the journal and the bearing are described by using a Hertzian-based contact force model and the Coulomb friction models, *** dynamic equations of the mechanism are derived based on the Lagrange equations of the first kind and the Baumgarte stabilization method. The frictional force is solved via the linear complementarity problem(LCP) algorithm and the trial-and-error ***, three numerical examples are given to show the influence of the two Coulomb friction models on the dynamic behavior of the mechanism. Numerical results show that due to the stick friction, the slider-crank mechanism may exhibit stick-slip motion and can balance at some special positions, while the mechanism with ideal joints cannot.

关键词： revolute clearance joint slider-crank mechanism stick friction stick-slip linear complementarity problem(LCP)

Non-smooth dynamic modeling and simulation of an unmannedbicycle on a curved pavement

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2022年第1期43卷 93-112页

作者： Kaiming ZHANG xudong zheng Zhang CHEN Bin LIANG Tianshu WANG Qi WANG School of Aeronautic Science and Engineering Beihang UniversityBeijing100083China Tsinghua Shenzhen International Graduate School Tsinghua UniversityShenzhenGuangdong Province518055China Department of Automation Tsinghua UniversityBeijing100084China School of Aerospace Engineering Tsinghua UniversityBeijing100084China

The non-smooth dynamic model of an unmanned bicycle is established to study the contact-separate and stick-slip non-smooth phenomena between wheels and the *** to the Carvallo-Whipple configuration,the unmanned bicycle is reduced to four rigid bodies,namely,rear wheel,rear frame,front fork,and front wheel,which are connected by perfect revolute *** interaction between each wheel and the ground is simplified as the normal contact force and the friction force at the contact point,and these forces are described by the Hunt-Crossley contact force model and the Lu Gre friction force model,*** to the characteristics of flat and curved pavements,calculation methods for contact forces and their generalized forces are *** dynamics of the system is modeled by the Lagrange equations of the first kind,a numerical solution algorithm of the dynamic equations is presented,and the Baumgarte stabilization method is used to restrict the drift of the *** correctness of the dynamic model and the numerical algorithm is verified in comparison with the previous *** feasibility of the proposed model is demonstrated by simulations under different motion states.

关键词： unmanned bicycle non-smooth dynamics Lu Gre model contact-impact stick-slip

A self-centering and stiffness-controlled MEMS accelerometer

在线全文

学校读者我要写书评

暂无评论

Microsystems & Nanoengineering 2024年第1期10卷 27-40页

作者： Yiming Jin Zhipeng Ma Ziyi Ye Mingkang Li xudong zheng Zhonghe Jin School of Aeronautics and Astronautics Zhejiang UniversityHangzhou 310013China Key Laboratory of Micro/Nano-Satellite Research of Zhejiang Province Hangzhou 310007PR China

This paper presents a high-performance MEMS accelerometer with a DC/AC electrostatic stiffness tuning capability based on double-sided parallel plates(DSPPs).DC and AC electrostatic tuning enable the adjustment of the effective stiffness and the calibration of the geometric offset of the proof mass,respectively.A dynamical model of the proposed accelerometer was developed considering both DC/AC electrostatic tuning and the temperature *** on the dynamical model,a self-centering closed loop is proposed for pulling the reference position of the forceto-rebalance(FTR)to the geometric center of *** self-centering accelerometer operates at the optimal reference position by eliminating the temperature drift of the readout circuit and nulling the net electrostatic tuning *** stiffness closed-loop is also incorporated to prevent the pull-in instability of the tuned low-stiffness accelerometer under a dramatic temperature ***-time adjustments of the reference position and the DC tuning voltage are utilized to compensate for the residue temperature drift of the proposed *** a result,a novel controlling approach composed of a self-centering closed loop,stiffness-closed loop,and temperature drift compensation is achieved for the accelerometer,realizing a temperature drift coefficient(TDC)of approximately 7μg/℃ and an Allan bias instability of less than 1μg.

关键词： stiffness electrostatic centering

Extraction mechanism and separation behaviors of low-concentration Nd^(3+) and Al^(3+) in P507-H_(2)SO_(4) system

维普期刊数据库评论

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 Rare Earths 2022年第6期40卷 952-957,I0004页

作者： Hongyuan Zhang Longsheng Zhao xudong zheng Depeng Liu Zongyu Feng Yongqi Zhang Xiaowei Huang National Engineering Research Center for Rare Earth Materials GRINM Group Co.Ltd.Beijing 100088China General Research Institute for Nonferrous Metals Beijing 100088China Grirem Advanced Materials Co. Ltd.Beijing 100088China Rare Earth Functional Materials(Xiong’an)Innovation Center Co. Ltd.Baoding 071700China

In order to clarify the solvent extraction and separation behaviors of rare earths and impurity of Al during the extraction and enrichment of low-concentration leach solution of ion-adsorption rare earth ore,the extraction mechanism and separation behaviors of Nd^(3+)and Al^(3+)in the Nd_(2)(SO_(4))_(3)-AI_(2)(SO_(4))_(3) mixed solution using P507 were studied in this *** extraction of Nd^(3+)and Al^(3+)follows the cation exchange *** the increase of the equilibrium pH,β_(Nd/Al) in the extraction of the Nd_(2)(SO_(4))_(3)-Al_(2)(SO_(4))_(3) mixed solution using P507 is always higher than that in the extraction of single Nd_(2)(SO_(4))_(3) and Al_(2)(SO_(4))_(3) *** can be attributed to the fact that the extraction of Nd^(3+)using P507 is much faster than that of Al^(3+),and Al^(3+)is more prone to be hydrolyzed at lower pH.β_(Nd/Al) in the extraction of the Nd_(2)(SO_(4))_(3)-Al_(2)(SO_(4))_(3) mixed solution decreases gradually with the increase of mixing time within the equilibrium pH range of *** extraction of Nd^(3+)using P507 is much faster than that of Al^(3+),but the stability of Al^(3+)-Ioaded organic phase is better than that of Nd^(3+)-loaded organic phase,thus Nd^(3+)in the Nd^(3+)-loaded organic phase is gradually replaced by Al^(3+)in the aqueous phase with the increase of mixing time.

关键词： Ion-adsorption rare earth ore Low-concentration rare earth Aluminum Extraction mechanism Separation factor

A quasi-automated generation control strategy for multiple energy storage systems to optimize low-carbon benefits

在线全文

学校读者我要写书评

暂无评论

Journal of Modern Power Systems and Clean Energy 2015年第1期3卷 93-102页

作者： Gangui YAN xudong zheng Gang MU Junhui LI Yang CUI Yue WANG School of Electrical Engineering Northeast Dianli UniversityJilin 132012China

Integrating a battery energy storage system(ESS)with a large wind farm can smooth the intermittent power obtained from the wind farm,but the smoothing function will not be achieved if multiple ESSs are used to smooth the fluctuations in individual wind power plants in a distributed ***,this study focuses on the development of a control strategy to optimize the use of multiple ESSs to accelerate the adoption of wind energy *** paper proposes a quasi-automated generation control(QAGC)strategy to coordinate multiple ESSs,which responds to the grid dispatch demand rather than smoothing out the intermittent power from individual wind *** aims of QAGC are to ensure that multiple ESSs provide a service that is as balanced as possible,so more wind power systems at various scales can be accepted by the grid,as well maximizing the low-carbon benefits of *** effectiveness of QAGC is demonstrated by using data from an actual gigawatt scale cluster of wind plants.

关键词： Control strategy Low-carbon benefits Multiple battery energy storage systems Quasi-automated generation control

Temperature Bias Drift Phase-Based Compensation for a MEMS Accelerometer with Stiffness-Tuning Double-Sided Parallel Plate Capacitors

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nanomanufacturing and Metrology 2023年第3期6卷 29-40页

作者： Mingkang Li Zhipeng Ma Tengfei Zhang Yiming Jin Ziyi Ye xudong zheng Zhonghe Jin School of Aeronautics and Astronautics Zhejiang UniversityHangzhou310013China Key Laboratory of Micro/Nano-Satellite Research of Zhejiang Province Hangzhou310007China

This paper reports an approach of in-operation temperature bias drift compensation based on phase-based calibration for a stiffness-tunable MEMS accelerometer with double-sided parallel plate(DSPP)*** temperature drifts of the components of the accelerometer are characterized,and analytical models are built on the basis of the measured drift *** reveal that the temperature drift of the acceleration output bias is dominated by the sensitive mechanical *** out-of-bandwidth AC stimulus signal is introduced to excite the accelerometer,and the interference with the acceleration measurement is *** demodulated phase of the excited response exhibits a monotonic relationship with the effective stiffness of the *** the proposed online compensation approach,the temperature drift of the effective stiffness can be detected by the demodulated phase and compensated in real time by adjusting the stiffness-tuning voltage of DSPP *** temperature drift coefficient(TDC)of the accelerometer is reduced from 0.54 to 0.29 mg/℃,and the Allan variance bias instability of about 2.8μg is not adversely ***,the pull-in resulting from the temperature drift of the effective stiffness can be *** can be further reduced to 0.04 mg/℃through an additional offline calibration based on the demodulated carrier phase representing the temperature drift of the readout circuit.

关键词： MEMS accelerometer Stiffness tuning Double-sided parallel plates Temperature drift compensation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

摩擦与滚阻对被动行走器步态影响的研究

力学学报 2020年第1期52卷 162-170页

作者：郑鹏王琪吕敬郑旭东北京航空航天大学航空科学与工程学院北京100083

本文研究了圆弧足被动行走器支撑足与地面间的摩擦系数和滚阻系数对被动行走器步态的影响.首先分别利用扩展的赫兹接触力模型和LuGre摩擦模型描述了支撑足与地面接触点处的法向支撑力和切向摩擦力,并考虑了行走过程中支撑足所受的滚动摩... 详细信息

本文研究了圆弧足被动行走器支撑足与地面间的摩擦系数和滚阻系数对被动行走器步态的影响.首先分别利用扩展的赫兹接触力模型和LuGre摩擦模型描述了支撑足与地面接触点处的法向支撑力和切向摩擦力,并考虑了行走过程中支撑足所受的滚动摩阻;其次利用第二类Lagrange方程推导出了该系统的动力学方程,并通过与已有成果的对比确定了合适的LuGre摩擦模型参数;最后仿真分析了摩擦系数和滚阻系数对被动行走器步态的影响.研究发现:摩擦系数的改变虽然对被动行走器行走的平均速度、步幅,以及支撑足接触点处的最大法向接触力的影响较小,但摩擦系数的减小会改变其行走步态类型,如发生倍周期分岔甚至混沌现象;然而,滚阻系数的改变会对行走器行走的平均速度、步幅,以及支撑足接触点处的最大法向接触力的影响较大,尚未发现滚阻系数的改变会引起其行走步态的变化.

关键词：被动行走器 LuGre摩擦模型滚动摩阻行走步态倍周期分岔

在线全文

学校读者我要写书评

暂无评论

论阿尔都塞唯物主义视野下的效力概念

北京师范大学学报（社会科学版） 2024年第5期 85-93页

作者：郑旭东北京师范大学价值与文化研究中心、哲学学院北京100875

“效力”是一个贯穿阿尔都塞文本并具有严格和精准的理论功能的概念。在马克思主义的语境中,对效力的强调意味着在作为决定性因素的经济基础之外,还要承认上层建筑“相对独立”的效力。按照阿尔都塞的观点,“过度决定”和黑格尔式简单... 详细信息

“效力”是一个贯穿阿尔都塞文本并具有严格和精准的理论功能的概念。在马克思主义的语境中,对效力的强调意味着在作为决定性因素的经济基础之外,还要承认上层建筑“相对独立”的效力。按照阿尔都塞的观点,“过度决定”和黑格尔式简单矛盾的区分,恰恰就在于前者应当被视作一个复杂的效力系统。只有从效力的角度出发,我们才能理解意识形态作为观念如何在再生产的过程中发挥功能,以及意识形态在何种意义上具有“物质性”:并非“物质的才是有效力的”,而是“有效力的就是物质的”。借助斯宾诺莎主义的资源,阿尔都塞基于效力概念肯定了意识形态的物质性,也同时呈现出一种对历史唯物主义的深化与发展。

关键词：阿尔都塞效力唯物主义意识形态斯宾诺莎

思想是否拥有特权?——论斯宾诺莎的双重平行论

在线全文

学校读者我要写书评

暂无评论

世界哲学 2023年第2期 60-67页

作者：郑旭东巴黎第八大学哲学学院

在近代哲学关于身心关系问题的讨论中,斯宾诺莎的平行论构想是其中的一个独特代表。在平行论的主张下,思想和广延之间不仅存在着真实的区分以及彼此的对应,而且在存在上具有平等的地位。但是,在特定语境中,斯宾诺莎似乎赋予了思想属性... 详细信息

在近代哲学关于身心关系问题的讨论中,斯宾诺莎的平行论构想是其中的一个独特代表。在平行论的主张下,思想和广延之间不仅存在着真实的区分以及彼此的对应,而且在存在上具有平等的地位。但是,在特定语境中,斯宾诺莎似乎赋予了思想属性某种特权:其一是“不对称性”难题,即思想的外延似乎等同于其他所有属性,大于任一属性;其二是“自反性”难题,即思想能够反思自身,而其他属性并不具有这种自反的特性。本文试图说明,对这些难题的解决依赖于对其平行论双重结构的梳理和区分。一旦证明斯宾诺莎的平行论具有本体论平行论和认识论平行论的双重结构,那么这些难题就不再构成挑战,而斯宾诺莎平行论的基本原则也能得到保全。

关键词：斯宾诺莎平行论身心关系思想

在线全文

学校读者我要写书评

暂无评论

西安市长安区新出唐《韦昶墓志》发微

考古与文物 2019年第1期 87-94页

作者：郑旭东西安市文物保护考古研究院

2015年8月,在西安市长安区高望堆村北,发掘了唐咸通四年(863年)韦昶墓。据墓志记载可知,韦昶为唐顺宗永贞年间(805年)宰相韦执谊之子。墓志记载了韦昶的出身和历官、家族谱系、宅地葬地等内容,补充了史书对韦昶生平的记载,订补了唐宰相... 详细信息

2015年8月,在西安市长安区高望堆村北,发掘了唐咸通四年(863年)韦昶墓。据墓志记载可知,韦昶为唐顺宗永贞年间(805年)宰相韦执谊之子。墓志记载了韦昶的出身和历官、家族谱系、宅地葬地等内容,补充了史书对韦昶生平的记载,订补了唐宰相韦执谊一族的谱系,反映了"二王八司马"事件对韦昶家族的影响。墓志中提及韦昶的宅地、葬地,为研究韦执谊等在长安的居住地和葬地,提供重要的线索。

关键词：韦昶墓志韦执谊京兆韦氏