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Isolation performances and optimization of triple quasi-zero stiffness isolators

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Science China(Physics,Mechanics & Astronomy) 2024年第7期67卷 124-141页

作者： Yuntian Zhang Guangnan Zhu Qingjie cao School of Astronautics Harbin Institute of TechnologyHarbin 150001China

In this paper,triple quasi-zero stiffness(QZS)passive vibration isolators whose restoring force curve has a three-stage softening effect are ***-coupled SD oscillators with three independent geometrical parameters are used as negative stiffness mechanisms to achieve QZS characteristics at the origin and symmetrical positions on both sides of the *** performances of different triple QZS isolators are analyzed to show influences of the selection of QZS regions away from the origin on the range of isolation *** optimizations of system parameters are carried out to get a larger range of small restoring force regions and small stiffness *** performances of two triple QZS isolators are discussed to show the influence of different Pareto optimization solutions through the comparisons with single and double QZS *** showed that triple QZS isolators have both the advantages of single and double QZS isolators which results in better isolation performances under both small and large excitation *** improvement in isolation performances for triple QZS isolators is found with the decrease in average stiffness due to the appearance of two symmetrical QZS regions away from the *** displacements of QZS regions away from the origin result in better isolation performances when excitation amplitude is large,and triple QZS characteristics are similar to double QZS isolators at this *** restoring forces of QZS regions away from the origin lead to better isolation performances when excitation amplitude is small,and triple QZS characteristics are similar to single QZS isolators at this *** with the decrease in average stiffness,the improvement of isolation performances shows a hysteresis phenomenon due to the difference between static and dynamic characteristics.

关键词： triple quasi-zero stiffness vibration isolation Pareto optimization force transmissibility geometrical nonlinear

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Lyapunov Conditions for Finite-Time Input-to-State Stability of Impulsive Switched Systems

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IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 1057-1059页

作者： Taixiang Zhang Jinde cao Xiaodi Li the School of Mathematics Southeast UniversityNanjing 210096China the School of Mathematics and Statistics Shandong Normal UniversityJinan 250014Chi

Dear Editor,This letter studies finite-time input-to-state stability(FTISS)for impulsive switched systems.A set of Lyapunov-based conditions are established for guaranteeing FTISS *** constituent modes governing continuous dynamics are FTISS and discrete dynamics involving impulses are destabilizing,the FTISS can be retained if impulsive-switching signals satisfy an average dwell-time(ADT)condition.

关键词： property impulsive satisfy

Key-Part Attention Retrieval for Robotic Object Recognition

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Tsinghua Science and Technology 2024年第3期29卷 644-655页

作者： Jierui Liu Zhiqiang cao Yingbo Tang State KeyLaboratory of Multimodal Artificial Intelligence Systems Institute of AutomationChinese Academy of SciencesBeijing100190China School of Artificial Intelligence University of Chinese Academy of SciencesBeijing 100049China

The ability to recognize novel objects with a few visual samples is critical in the robotic *** methods mainly concern the recognition of inter-category objects,however,the object recognition fromdifferent sub-classes within the same category remains challenging due to their similar *** thispaper,we propose a key-part attention retrieval solution to distinguish novel objects of different sub-classesaccording to a few samples without ***,an object encoder,including convolutional neuralnetwork with attention and key-part aggregation,is designed to generate object attention map and extract theobject-level embedding,where object attention map from the middle stage of the backbone is used to guide thekey-part ***,to overcome the non-differentiability drawback of key-part attention,the objectencoder is trained in a two-step scheme,and a more stable object-level embedding is *** this basis,the potential objects are located from a scene image by mining connected domains of the attention *** the embedding of each potential object and embeddings from support data,the recognition of thepotential objects is *** effectiveness of the proposed method is verified by experiments.

关键词： key-part attention retrieval robotic object recognition

Sub-10-nm-sized Au@AuxIr1-x metal-core/alloy-shell nanoparticles as highly durable catalysts for acidic water splitting

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National Science Review 2024年第4期11卷 130-140页

作者： Huimin Wang Zhe-ning Chen Yuanyuan Wang Dongshuang Wu Minna cao Fanfei Sun Rong cao State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences University of Chinese Academy of Sciences School of Materials Science and Engineering Nanyang Technological University Shanghai Synchrotron Radiation Facility Shanghai Institute of Applied Physics Chinese Academy of Sciences Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China

The absence of efficient and durable catalysts for oxygen evolution reaction（OER） is the main obstacle to hydrogen production through water splitting in an acidic ele ***,we report a controllable synthesis method of surface IrOxwith changing Au/Ir compositions by constructing a range of sub-10-nm-sized core-shell nanocatalysts composed of an Au core and AuxIr1-xalloy *** particular,Au@Au0.43Ir0.57exhibits 4.5 times higher intrinsic OER activity than that of the commercial Ir/*** X-ray-based spectroscopies,electron microscopy and density functional theory calculations revealed a balanced binding of reaction intermediates with enhanced *** water-splitting cell using a load of 0.02 mgIr/cm2of Au@Au0.43Ir0.57as both anode and cathode can reach 10 mA/cm2at 1.52 V and maintain activity for at least194 h,which is better than the cell using the commercial couple Ir/C‖Pt/C（1.63 V,0.2 h）.

关键词： controllable synthesis of surface IrOx oxygen evolution reaction acidic water splitting catalytic stability transition metal catalysts

Superior efficiency and stability of YbO_(x)-enhanced perovskite solar cells

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Science China Materials 2024年第4期67卷 1356-1358页

作者： Qifeng Zhang Guozhong cao Department of Electrical and Computer Engineering North Dakota State UniversityFargoND 58108-6050USA Department of Materials Science and Engineering University of WashingtonSeattleWA 98195-2120USA

Perovskite solar cells represent a revolutionary class of photovoltaic devices that have gained substantial attention for their exceptional performance and potential to provide an affordable and efficient solution for harnessing solar energy. These cells utilize perovskite-structured materials, typically hybrid organicinorganic lead halide compounds, as the light-absorbing layer.

关键词： energy perovskite stability

Distributed Heterogeneous Multi-Agent Optimization with Stochastic Sub-Gradient

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Journal of Systems Science & Complexity 2024年第4期37卷 1470-1487页

作者： HU Haokun MO Lipo cao Xianbing School of Mathematics and Statistics Central South UniversityChangsha 410083China School of Mathematics and Statistics Beijing Technology and Business UniversityBeijing 100048China Research Centre for Agri-Product Quality Traceability Beijing Technology and Business UniversityBeijing 100048China School of Computer and Artificial Intelligence Beijing Technology and Business UniversityBeijing 100048China China Food Flavor and Nutrition Health Innovation Center Beijing Technology and Business UniversityBeijing 100048China

This paper studies the optimization problem of heterogeneous networks under a timevarying *** agent only accesses to one local objective function,which is *** improved algorithm with noisy measurement of local objective functions' sub-gradients and additive noises among information exchanging between each pair of agents is designed to minimize the sum of objective functions of all *** weaken the effect of these noises,two step sizes are introduced in the control *** graph theory,stochastic analysis and martingale convergence theory,it is proved that if the sub-gradients are uniformly bounded,the sequence of digraphs is balanced and the union graph of all digraphs is joint strongly connected,then the designed control protocol can force all agents to find the global optimal point almost *** last,the authors give some numerical examples to verify the effectiveness of the stochastic sub-gradient algorithms.

关键词： Communication noises distributed stochastic optimization heterogeneous networks subgradient measurement noises

Fatigue-resistant Hydrogels

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Chemical Research in Chinese Universities 2024年第1期40卷 64-77页

作者： LI Luofei LEI Hai cao Yi Collaborative Innovation Center of Advanced Microstructures National Laboratory of Solid State MicrostructureDepartment of PhysicsNanjing UniversityNanjing 210093P.R.China Department of Physics Zhejiang UniversityHangzhou 310027P.R.China

Hydrogels have been extensively studied for applications in various fields, such as tissue engineering and soft robotics, as determined by their mechanical properties. The mechanical design of hydrogels typically focuses on the modulus, toughness, and deformability. These characteristics play important roles and make great achievements for hydrogel use. In recent years, a growing body of research has concentrated on the fatigue property of hydrogels, which determines their resistance to crack propagation in the networks during cyclic mechanical loads for applications. However, knowledge of hydrogel fatigue behavior remains notably deficient. Here, we present a brief overview of the fatigue behavior of hydrogels, encompassing the general experimental methods to measure the fatigue property and fundamental theoretical calculation models. Then, we highlight multiple strategies to enhance the fatigue resistance of hydrogels. Finally, we present our perspectives on fatigue-resistant hydrogels, outstanding challenges and potential directions for future research.

关键词： Hydrogel Fatigue-resistant Fracture

Grassland-type ecosystem stability in China differs under the influence of drought and wet events

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Journal of Arid Land 2024年第5期16卷 615-631页

作者： cao Wenyu BAI Jianjun YU Leshan School of Geography and Tourism Shaanxi Normal UniversityXi'an 710119China International Business School Shaanxi Normal UniversityXi'an 710119China

Ecological stability is a core issue in ecological research and holds significant implications forhumanity. The increased frequency and intensity of drought and wet climate events resulting from climatechange pose a major threat to global ecological stability. Variations in stability among different ecosystemshave been confirmed, but it remains unclear whether there are differences in stability within the sameterrestrial vegetation ecosystem under the influence of climate events in different directions and ***'s grassland ecosystem includes most grassland types and is a good choice for studying this *** study used the Standardized Precipitation Evapotranspiration Index-12 (SPEI-12) to identify thedirections and intensities of different types of climate events, and based on Normalized DifferenceVegetation Index (NDVI), calculated the resistance and resilience of different grassland types for 30consecutive years from 1990 to 2019 (resistance and resilience are important indicators to measurestability). Based on a traditional regression model, standardized methods were integrated to analyze theimpacts of the intensity and duration of drought and wet events on vegetation stability. The resultsshowed that meadow steppe exhibited the highest stability, while alpine steppe and desert steppe had thelowest overall stability. The stability of typical steppe, alpine meadow, temperate meadow was at anintermediate level. Regarding the impact of the duration and intensity of climate events on vegetationecosystem stability for the same grassland type, the resilience of desert steppe during drought was mainlyaffected by the duration. In contrast, the impact of intensity was not significant. However, alpine steppewas mainly affected by intensity in wet environments, and duration had no significant impact. Ourconclusions can provide decision support for the future grassland ecosystem governance.

关键词： grassland ecosystem stability resistance resilience different climate types drought climate event wet climate event

Accuracy of numerical relativity waveforms with respect to space-based gravitational wave detectors

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Communications in Theoretical Physics 2024年第1期76卷 82-95页

作者： Zun Wang Junjie Zhao Zhoujian cao Institute for Frontiers in Astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China Department of Astronomy Beijing Normal UniversityBeijing 100875China School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUCASHangzhou 310024China

As with the laser interferometer gravitational-wave observatory(LIGO),the matched filtering technique will be critical to the data analysis of gravitational wave detection by space-based detectors,including LISA,Taiji and *** templates are the basis for such matched filtering *** construct ready-to-use waveform templates,numerical relativity waveforms are a starting ***,the accuracy issue of numerical relativity waveforms is critically *** are many investigations regarding this issue with respect to *** unfortunately there are few results on this issue with respect to space-based *** current paper investigates this *** results indicate that the existing numerical relativity waveforms are as accurate as 99%with respect to space-based detectors,including LISA,Taiji and *** an accuracy level is comparable to that with respect to LIGO.

关键词： numerical relativity gravitational wave binary black hole