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High-static-low-dynamic stiffness isolator based on an electromagnetic negative stiffness spring with long linear stroke

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Science china(Technological Sciences) 2024年第3期67卷 740-752页

作者： YUAN ShuJin WU YaJun SONG DaiPing PU HuaYan MOU LiSheng HOU Lei ZHAO JingLei LI XuePing LUO Jun WU Jie HUANG XiaoXu state key laboratory of Mechanical Transmissions Chongqing UniversityChongqing 400044China china aerodynamics research and development center Mianyang 621000China College of Materials Science and Engineering Chongqing UniversityChongqing 400044China

Negative stiffness mechanisms can improve low-frequency vibration isolation performance and have been widely used in the vibration isolation of precision equipment. However, the negative stiffness mechanism usually introduces a nonlinear stiffness,resulting in a nonlinear response and worsening the vibration isolation performance, especially under large amplitude *** this paper, an electromagnetic spring with linear negative stiffness(ESLNS) is proposed, in which the antagonistic ampere forces of the energized coils are used to generate negative stiffness within a long linear stroke. The magnetic field distribution is improved through the design of the magnetic circuit, thereby increasing the stiffness generation efficiency. The stiffness can be adjusted bidirectionally by current within the range of positive and negative stiffness. An electromagnetic stiffness model was established based on the equivalent magnetic circuit method. Experimental measurements verified the accuracy of the model and proved the linearity of the electromagnetic spring. A vibration isolator with high static and low dynamic stiffness(HSLDS) based on the ESLNS is designed and tested. The experimental results prove that the introduction of the ESLNS can effectively expand the isolation frequency band without changing the equilibrium position. Moreover, the vibration isolator with ESLNS does not produce nonlinear response. The proposed electromagnetic spring with linear negative stiffness extends the application range of HSLDS isolators to a large amplitude vibration environment.

关键词： linear negative stiffness mechanism low-frequency vibration isolation electromagnetic spring vibration control

Time-Domain Analysis of Body Freedom Flutter Based on 6DOF Equation

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工程与科学中的计算机建模(英文) 2024年第1期138卷 489-508页

作者： Zhehan Ji Tongqing Guo Di Zhou Zhiliang Lu Binbin Lyu key laboratory of Unsteady aerodynamics and Flow Control Ministry of Industry and Information TechnologyNanjing University of Aeronautics and AstronauticsNanjing210016China High Speed aerodynamics Institute China Aerodynamics Research and Development CenterMianyang621000China

The reduced weight and improved efficiency of modern aeronautical structures result in a decreasing separation of frequency ranges of rigid and elastic ***,a high-aspect-ratio flexible flying wing is prone to body freedomflutter(BFF),which is a result of coupling of the rigid body short-periodmodewith 1st wing *** prediction of the BFF characteristics is helpful to reflect the attitude changes of the vehicle intuitively and design the active flutter suppression control *** of using the rigid body mode,this work simulates the rigid bodymotion of the model by using the six-degree-of-freedom(6DOF)equation.A dynamicmesh generation strategy particularly suitable for BFF simulation of free flying aircraft is *** accurate Computational Fluid Dynamics/Computational Structural Dynamics/six-degree-of-freedom equation(CFD/CSD/6DOF)-based BFF prediction method is ***,the time-domain CFD/CSD method is used to calculate the static equilibrium state of the *** on this state,the CFD/CSD/6DOF equation is solved in time domain to evaluate the structural response of *** combinedwith the variable stiffnessmethod,the critical flutter point of the model is *** method is applied to the BFF calculation of a flyingwing *** calculation results of the BFF characteristics of the model agree well with those fromthe modalmethod andNastran ***,the method is used to analyze the influence factors of *** analysis results show that the flutter speed can be improved by either releasing plunge constraint or moving the center ofmass forward or increasing the pitch inertia.

关键词： Body freedom flutter time-domain CFD/CSD/6DOF method dynamic mesh generation strategy aeroelasticity

Observing strain glass transition in Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)high entropy alloy with Elinvar effect

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Journal of Materials Science & Technology 2024年第1期168卷 16-23页

作者： Kaichao Zhang Kai Wang Bin Wang Chao Lv Jiaxing Zheng Guanqi Li Yu Fu Wenlong Xiao Qingqing Cai Xutao Nie Yingfeng Shao Huilong Hou Xinqing Zhao School of Materials Science and Engineering Beihang UniversityBeijing 100191China china aerodynamics research and development center Mianyang 621000China state key laboratory of Nonlinear Mechanics Chinese Academy of SciencesInstitute of MechanicsBeijing 100190China Tianmushan laboratory(Zhejiang Provincial laboratory for Aviation) Hangzhou 310000China

Exploring the phase transition of high entropy alloys(HEAs)with multiple major elements is of great importance for understanding the underlying physical *** martensitic phase tran-sition has been frequently reported in HEAs,however,nanoscale microstructural phase evolution has not been investigated to the same ***,we have prepared the Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA and investi-gated the strain glass transition and its associated properties using dynamic mechanical analysis and mi-crostructure *** have found that the elastic modulus in Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA deviates from Wachtman’s equation and observed the Elinvar effect in the form of temperature-independent mod-ulus in the temperature range from 150 K to 450 K and frequency-dependence modulus around 220 *** strain glass transition has been evidenced in Ti_(33)Nb_(15)Zr_(25)Hf_(25)O_(2)HEA by the formation and growth of nano-sized domains during in-situ transmission electron microscopy(TEM)cooling,and substantiated by the broken ergodicity during zero-field-cooling/*** strain glass transition is believed to account for the Elinvar effect,where the modulus hardening of nano-sized domains compensates dynam-ically with the modulus softening of the transformable matrix.

关键词： High entropy alloys Strain glass transition Elinvar effect Microstructural evolution Nanodomains

Experimental Study on Mixed-Mode(Ⅰ–Ⅱ)Fracture Toughness of Freshwater Ice

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Acta Mechanica Solida Sinica 2024年第2期37卷 252-264页

作者： Yaozhong Xu Mao Zhou Xian Yi Wen Hua Jiuzhou Huang Wenyu Zhang Shiming Dong key laboratory of Deep Underground Science and Engineering Ministry of EducationCollege of Architecture and EnvironmentSichuan UniversityChengdu610065China Failure Mechanics and Engineering Disaster Prevention key laboratory of Sichuan Province Sichuan UniversityChengdu610065China china aerodynamics research and development center/Low Speed aerodynamics research Institute Mianyang621000China College of Mechanical and Electrical Engineering Xichang UniversityXichang615000China

In recent years,the issue of aircraft icing has gained widespread *** breaking and detachment of dynamic ice can pose a threat to flight ***,the shedding and fracture mechanisms of dynamic ice are unclear and cannot meet the engineering needs of ice-shedding hazard ***,studying the fracture toughness of ice bodies has extremely important practical *** address this issue,this article uses a centrally cracked Brazilian disk(CCBD)specimen to measure the pure modeⅠtoughness and pure modeⅡfracture toughness of freshwater ice at different loading *** mixed-mode(Ⅰ–Ⅱ)fracture characteristics of ice are discussed,and the experimental results are compared and analyzed with the theoretical values of the generalized maximum tangential stress(GMTS)criterion considering the influence of *** results indicated that as the loading rate increases,the pure modeⅠtoughness and pure modeⅡfracture toughness of freshwater ice decrease,and the fracture toughness of freshwater ice is more sensitive to the loading rate.Ⅰn terms of fracture criteria,the theoretical value of the ratio of pure modeⅡfracture toughness to pure modeⅠfracture toughness based on the GMTS criterion is in good agreement with the experimental value,while the theoretical value based on the maximum tangential stress(MTS)criterion deviates significantly from the experimental value,indicating that the GMTS criterion considering the influence of T-stress can better predict the experimental results.

关键词： Freshwater ice Fracture criteria Centrally cracked Brazilian disk(CCBD) Mixed-mode(Ⅰ-Ⅱ) Loading rate

Adhesion strength of tetrahydrofuran hydrates is dictated by substrate stiffness

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Petroleum Science 2024年第1期21卷 667-673页

作者： Yan-Wen Lin Tong Li Yi Zhang Wei-Wei Yan Xiao-Ming Chen Zhi-Sen Zhang Jian-Yang Wu Department of Physics Research Institute for Biomimetics and Soft MatterJiujiang Research Institute and Fujian Provincial Key Laboratory for Soft Functional Materials ResearchXiamen UniversityXiamen361005FujianChina key laboratory of Marine Materials and Related Technologies Zhejiang Key Laboratory of Marine Materials and Protective TechnologiesNingbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo315201ZhejiangChina key laboratory of Icing and Anti/De-icing China Aerodynamics Research and Development CenterMianyang621000SichuanChina Micro-and Nano-technology research center State Key Laboratory for Manufacturing Systems EngineeringXi’an Jiaotong UniversityXi’an710049ShaanxiChina Electronic Materials research Lab Key Laboratory of the Ministry of EducationXi’an Jiaotong UniversityXi’an710049ShaanxiChina NTNU Nanomechanical Lab Norwegian University of Science and Technology(NTNU)Trondheim7491Norway

Understanding the hydrate adhesion is important to tackling hydrate accretion in ***,the relationship between the Tetrahydrofuran(THF)hydrate adhesion strength(AS)and surface stiffness on elastic coatings is systemically examined by experimental shear force measurements and theoretical *** mechanical factor-elastic modulus of the coatings greatly dictates the hydrate AS,which is explained by the adhesion mechanics theory,beyond the usual factors such as wettability and structural ***,the hydrate AS increases with reducing the thickness of the elastic coatings,resulted from the decrease of the apparent surface elastic *** effect of critical thickness for the elastic materials with variable elastic modulus on the hydrate AS is also *** study provides deep perspectives on the regulation of the hydrate AS by the elastic modulus of elastic materials,which is of significance to design anti-hydrate surfaces for mitigation of hydrate accretion in petro-pipelines.

关键词： Hydrate Adhesion strength Elastic modulus Coatings

Exploring the Mechanism,Advancements,and Application of Thermogalvanic Effect in Hydrogels

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Chinese Journal of Chemistry 2024年第5期42卷 543-556页

作者： Xiaoyu Yang Peng Wang Xiaolong Wu Yongli Liao Senyun Liu Wei Duan Ying Yue School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBaodingHebei071000 China Hebei key laboratory of Electric Machinery Health Maintenance & Failure Prevention North China Electric Power UniversityBaodingHebei071003 China Electric Power research Institute China South Power GridGuangzhouGuangdong510000 China key laboratory of Icing and Anti/De-icing China Aerodynamics Research and Development CenterMianyangSichuan621000 China

The issue of energy consumption has garnered significant interest due to its excessive ***,thermoelectric devices have been getting increased attention,as they can harness waste heat from various sources,such as solar radiation,human body,and industrial ***,the recovery of low-grade heat has been a challenge,resulting in unsustainable energy use and significant *** considerable advances have been made in thermoelectric materials in recent decades,the majority of these devices still primarily employ ***,the emergence of quasi-solid-state thermoelectric materials represents a novel development with profound promise for the environment and *** materials offer several advantages,such as improved energy conversion capacities,cost-effectiveness,versatility,and scalability,to support increased ***,this review explores the application of thermoelectric materials in self-powered sensors,integrated modules,and heat harvesting ***,the potential of high-performance thermocouples based on thermogalvanic effects is assessed,along with the challenges that must be overcome to realize this goal.

关键词： Hydrogel Thermogalvanic effect Thermochemistry Electrolytes Flexible electronics

research on the quasi-isentropic driving model of aluminized explosives in the detonation wave propagation direction

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Defence Technology（防务技术） 2024年第2期32卷 596-618页

作者： Hongfu Wang Yan Liu Fan Bai Chao He Yingliang Xu Qiang Zhou Chuan Xiao Fenglei Huang state key laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China china research and development Academy of Machinery Equipment Beijing100089China Beijing Institute of Technology Chongqing Innovation center Chongqing401120China

Taking CL-20(Hexanitrohexaazaisowurtzitane)-based aluminized explosives with high gurney energy as the research object, this research experimentally investigates the work capability of different aluminized explosive formulations when driving metal flyer plates in the denotation wave propagation *** research results showed that the formulations with 43 μm aluminum(Al) powder particles(The particle sizes of Al powder were in the range of 2~43 μm) exhibited the optimal performance in driving flyer plates along the denotation wave propagation direction. Compared to the formulations with Al powder 13 μm, the formulations with Al powder 2 μm delivered better performance in accelerating metal flyer plates in the early stage, which, however, turned to be poor in the later stage. The CL-20-based explosives containing 25% Al far under-performed those containing 15% Al. Based on the proposed quasi-isentropic hypothesis, relevant isentropy theories, and the functional relationship between detonation parameters and entropy as well as Al reaction degree, the characteristic lines of aluminized explosives in accelerating flyer plates were theoretically studied, a quasi-isentropic theoretical model for the aluminized explosive driving the flyer plate was built and the calculation methods for the variations of flyer plate velocity, Al reaction degree, and detonation product parameters with time and axial positions were developed. The theoretical model built is verified by the experimental results of the CL-20-based aluminized explosive driving flyer plate. It was found that the model built could accurately calculate the variations of flyer plate velocity and Al reaction degree over time. In addition, how physical parameters including detonation product pressure and temperature varied with time and axial positions was identified. The action time of the positive pressure after the detonation of aluminized explosives was found prolonged and the downtrend of the temperature was

关键词： Aluminized explosive Flyer plate experiment Quasi-isentropic theoretical model Al reaction Driving characteristics

High-speed penetration of ogive-nose projectiles into thick concrete targets:Tests and a projectile nose evolution model

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Defence Technology（防务技术） 2024年第2期32卷 553-571页

作者： Xu Li Yan Liu Junbo Yan Zhenqing Shi Hongfu Wang Yingliang Xu Fenglei Huang state key laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China Beijing Institute of Technology Chongqing Innovation center Chongqing401120China china research and development Academy of Machinery Equipment Beijing100089China

The majority of the projectiles used in the hypersonic penetration study are solid flat-nosed cylindrical projectiles with a diameter of less than 20 *** study aims to fill the gap in the experimental and analytical study of the evolution of the nose shape of larger hollow projectiles under hypersonic *** the hypersonic penetration test,eight ogive-nose AerMet100 steel projectiles with a diameter of 40 mm were launched to hit concrete targets with impact velocities that ranged from 1351 to 1877 m/*** erosion of the projectiles was observed during high-speed penetration of heterogeneous targets,and apparent localized mushrooming occurred in the front nose of recovered *** examining the damage to projectiles,a linear relationship was found between the relative length reduction rate and the initial kinetic energy of projectiles in different penetration ***,microscopic analysis revealed the forming mechanism of the localized mushrooming phenomenon for eroding penetration,i.e.,material spall erosion abrasion mechanism,material flow and redistribution abrasion mechanism and localized radial upsetting deformation ***,a model of highspeed penetration that included erosion was established on the basis of a model of the evolution of the projectile nose that considers radial upsetting;the model was validated by test data from the literature and the present *** upon the impact velocity,v0,the projectile nose may behave as undistorted,radially distorted or *** to the effects of abrasion of the projectile and enhancement of radial upsetting on the duration and amplitude of the secondary rising segment in the pulse shape of projectile deceleration,the predicted DOP had an upper limit.

关键词： High-speed penetration Concrete target Erosion Projectile nose evolution model

A survey on federated learning:a perspective from multi-party computation

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Frontiers of Computer Science 2024年第1期18卷 93-103页

作者： Fengxia LIU Zhiming ZHENG Yexuan SHI Yongxin TONG Yi ZHANG Institute of Artificial Intelligence and key laboratory of Mathematics Informatics Behavioral Semantics Beihang UniversityBeijing 100191China state key laboratory of Software development Environment and Advanced Innovation center for Future Blockchain and Privacy Computing Beihang UniversityBeijing 100191China Pengcheng laboratory Shenzhen 518055China Zhongguancun laboratory Beijing 100190China Institute for Mathematical Sciences and Engineering research center of Financial Computing and Digital Engineering Renmin University of ChinaBeijing 100872China

Federated learning is a promising learning paradigm that allows collaborative training of models across multiple data owners without sharing their raw *** enhance privacy in federated learning,multi-party computation can be leveraged for secure communication and computation during model *** survey provides a comprehensive review on how to integrate mainstream multi-party computation techniques into diverse federated learning setups for guaranteed privacy,as well as the corresponding optimization techniques to improve model accuracy and training *** also pinpoint future directions to deploy federated learning to a wider range of applications.

关键词： sfederated learning multi-party ycomputation privacy-preserving data mining distributed learning