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Polyolefin vitrimers bearing acetoacetate functionality

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Science China Chemistry 2024年第11期67卷 3861-3867页

作者： Zihao Wang Yue Liu Wenmin Pang ao chen Min chen Chinese Academy of Sciences (CAS) Key Laboratory of Soft Matter Chemistry Department of Polymer Science and Engineering University of Science and Technology of China Institutes of Physical Science and Information technology Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education Anhui University

Polyolefin vitrimers are polymer networks bearing reversible covalent crosslinking points, enabling them to be reprocessed and recycled. In this contribution, a series of polyolefin vitrimers were designed based on the acetoacetate-functionalized polyolefin copolymers, which were produced through the direct copolymerization of ethylene with polar comonomers using a phosphinesulfonate palladium catalyst. The pendant acetoacetate group could mediate several characteristic reactions, such as the Michael addition reaction, ketone-amine condensation and metal coordination reaction. As such, structurally adjustable polyolefin vitrimers can be accessed by introducing various dynamic crosslinking bonds, including disulfide exchange, transamination of vinylogous urethane and labile metal coordination bond. The utilization of different crosslinking reactions and the mole ratio of crosslinkers significantly impact the material properties of the resultant polymers. Specifically, the generated polyolefin vitrimers demonstrated excellent reprocessability and closed-loop recycling properties. The study in this work provides an efficient strategy to access various polyolefin vitrimers.

关键词： polyolefin vitrimers acetoacetate group polar monomer olefin copolymerization

Cluster-Based Massive Access for Massive MIMO Systems

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China Communications 2024年第1期21卷 24-33页

作者： Shiyu Liang Wei chen Zhongwen Sun ao chen Bo Ai State Key Laboratory of Advanced Rail Autonomous Operation Beijing Jiaotong UniversityBeijing 100091China School of Electronic and Information Engineering Beijing Jiaotong UniversityBeijing 100091China Frontiers Science Center for Smart High-speed Railway System Beijing Jiaotong UniversityBeijing 100091China Key Laboratory of Railway Industry of Broadband Mobile Information Communications Beijing Jiaotong UniversityBeijing 100091China Beijing Engineering Research Center of High-speed Railway Broadband Mobile Communications Beijing Jiaotong UniversityBeijing 100091China School of Information Engineering Zhengzhou UniversityZhengzhou 450001China

Massive machine type communication aims to support the connection of massive devices,which is still an important scenario in *** this paper,a novel cluster-based massive access method is proposed for massive multiple input multiple output *** exploiting the angular domain characteristics,devices are separated into multiple clusters with a learned cluster-specific dictionary,which enhances the identification of active *** detected active devices whose data recovery fails,power domain nonorthogonal multiple access with successive interference cancellation is employed to recover their data via *** results show that the proposed scheme and algorithm achieve improved performance on active user detection and data recovery.

关键词： compressive sensing dictionary learning multiuser detection random access

Multi-blade rubbing characteristics of the shaft-disk-blade-casing system with large rotation

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Applied Mathematics and Mechanics(English Edition) 2024年第1期45卷 111-136页

作者： Zhiyuan WU Linchuan ZHao Han YAN Ge YAN ao chen Wenming ZHANG State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong UniversityShanghai 200240China Shanghai Institute of Aerospace Systems Engineering Shanghai 201108China

Blade rubbing faults cause detrimental impact on the operation of aeroengines. Most of the existing studies on blade rubbing in the shaft-disk-blade-casing(SDBC) system have overlooked the elastic deformation of the blade, while some only consider the whirl of the rotor, neglecting its spin. To address these limitations, this paper proposes a dynamic model with large rotation for the SDBC system. The model incorporates the spin and whirl of the rotor, enabling the realistic reproduction of multiblade rubbing faults. To verify the accuracy of the SDBC model with large rotation and demonstrate its capability to effectively consider the rotational effects such as the centrifugal stiffening and gyroscopic effects, the natural characteristics and dynamic responses of the proposed model are compared with those obtained from reported research and experimental results. Furthermore, the effects of the rotating speed, contact stiffness,and blade number on the dynamic characteristics of the SDBC system with multi-blade rubbing are investigated. The results indicate that the phase angle between the rotor deflection and the unbalance excitation force increases with the increasing rotating speed,which significantly influences the rubbing penetration of each blade. The natural frequency of the SDBC system with rubbing constrain can be observed in the acceleration response of the casing and the torsional response of the shaft, and the frequency is related to the contact stiffness. Moreover, the vibration amplitude increases significantly with the product of the blade number under rubbing, and the rotating frequency approaches the natural frequency of the SDBC system. The proposed model can provide valuable insight for the fault diagnosis of rubbing in bladed rotating machinery.

关键词： shaft-disk-blade-casing(SDBC) large rotation spin and whirl multi-blade rubbing rotational effect

Advances in sodium-ion batteries at low-temperature: Challenges and strategies

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Journal of Energy Chemistry 2024年第3期90卷 518-539,I0012页

作者： Haoran Bai Xiaohui Zhu Huaisheng ao Guangyu He Hai Xiao Yinjuan chen Key Laboratory of Advanced Catalytic Materials and technology Advanced Catalysis and Green Manufacturing Collaborative Innovation CenterChangzhou UniversityChangzhou 213164JiangsuChina Department of Chemistry Tsinghua UniversityBeijing 100084China

With the continuing boost in the demand for energy storage,there is an increasing requirement for batteries to be capable of operation in extreme environmental ***-ion batteries(SIBs) have emerged as a highly promising energy storage solution due to their promising performance over a wide range of temperatures and the abundance of sodium resources in the earth's *** to lithiumion batteries(LIBs),although sodium ions possess a larger ionic radius,they are more easily desolvated than lithium *** rthermore,SIBs have a smaller Stokes radius than lithium ions,resulting in improved sodium-ion mobility in the ***,SIBs demonstrate a significant decrease in performance at low temperatures(LT),which constrains their operation in harsh weather *** the increasing interest in SIBs,there is a notable scarcity of research focusing specifically on their mechanism under LT *** review explores recent research that considers the thermal tolerance of SIBs from an inner chemistry process perspective,spanning a wide temperature spectrum(-70 to100℃),particularly at LT *** addition,the enhancement of electrochemical performance in LT SIBs is based on improvements in reaction kinetics and cycling stability achieved through the utilization of effective electrode materials and electrolyte ***,the safety concerns associated with SIBs are addressed and effective strategies are proposed for mitigating these ***,prospects conducted to extend the environmental frontiers of commercial SIBs are discussed mainly from three viewpoints including innovations in materials,development and research of relevant theoretical mechanisms,and intelligent safety management system establishment for larger-scale energy storage SIBs.

关键词： Low-temperature Sodium-ion batteries Reaction kinetics Cycle stability Safety concerns of Sodium-ion batteries

Europium-bearing organic framework with excellent X-ray scintillating luminescence

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Journal of Rare Earths 2024年第2期42卷 251-255,I0001页

作者： Yugang Zhang Lanhua chen Xia Wang Wei Liu Shu'ao Wang State Key Laboratory of Radiation Medicine and Protection School for Radiological and Interdisciplinary Sciences(RAD-X)and Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education InstitutionsSoochow UniversitySuzhou215123China School of Environmental and Materials Engineering Yantai UniversityYantai264005China

Two europium-bearing organic frameworks,termed as EuTPO-1 and EuTPO-2(H_(3)TPO=tris(4-carboxylphenyI)-phosphineoxide),are reported in this work.A series of characterizations of EuTPO-1and EuTPO-2,such as X-ray crystallography and photoluminescence spectroscopy,was performed to expatiate their structure and physicochemical *** of them are constructed by dimers of the europium-oxygen subunit of [Eu_(2)O_(16)] and TPO *** from high X-ray stopping attenuation and excellent luminescence efficiency,they emit sufficient luminescence when irradiated with ***,they possess stable light outputs when exposed to high humidities and strong radiation dose,outperforming the commercial scintillator CsI:*** result paves the way for developing new scintillator and enriches the compound of europium-bearing organic framework with X-ray scintillating luminescence.

关键词： Metal-organic frameworks Scintillating material Luminescence efficiency Rare earths

Design of low-frequency circular metastructure isolators with high-load-bearing capacity

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Chinese Journal of Aeronautics 2024年第10期37卷 207-220页

作者： Ning chen Zhichun YANG te YANG Yizhou SHEN Wei TIAN Yanlong XU School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China National Key Laboratory of Strength and Structural Integrity Xi’an 710065China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi’an 710049China

Traditional vibration isolation structures cannot work effectively for low-frequency vibration under heavy loads,due to the inherent contradiction between the high-static and lowdynamic stiffness of these *** the challenge can be effectively addressed by introducing a negative stiffness mechanism,the existing structures inevitably have complex ***,a class of man-made structures with both extraordinary mechanical properties and simple configurations,provide a new insight for low-frequency vibration isolation *** this paper,circular metastructure isolators consisting of some simple beams are designed for low-frequency vibration,including a single-layer isolator and a double-layer isolator,and their static and dynamic characteristics are studied,*** the static characteristic,the force–displacement and stiffness–displacement curves are obtained by finite element simulation;for the dynamic characteristic,the vibration transmissibility curves are obtained analytically and *** result shows that the circular nonlinear single-layer isolator has excellent lowfrequency isolation performance,and the isolation frequency band will decrease about 20 Hz when the isolated mass is fixed at 1.535 kg,compared with a similar circular linear *** static and dynamic properties are well verified through *** work provides an innovative approach for the low-frequency vibration isolation and has wide potential applications in aeronautics.

关键词： Isolator Low-frequency Curved beam Metastructure Stiffness

Photoluminescence and photothermal conversion in boric acid derived carbon dots for targeted microbial theranostics

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Chinese Chemical Letters 2024年第9期35卷 232-237页

作者： Yiqiao chen ao Liu Biwen Yang Zhenzhen Li Binggang Ye Zhouyi Guo Zhiming Liu Haolin chen Department of Anesthesiology General Hospital of Southern Theater Command of People’s Liberation ArmyGuangzhou 510010China MOE Key Laboratory of Laser Life Science&Guangdong Provincial Key Laboratory of Laser Life Science College of BiophotonicsSouth China Normal UniversityGuangzhou 510631China Healthy Medical Engineering technology Research Center Guangdong Food and Drug Vocational CollegeGuangzhou 510520China

Theranostic carbon dots(CDs)have attracted widespread attention recently due to their tunable optical properties and diverse *** fluorescent imaging application,the photothermal property endows CDs with the potential for microbial ***,realization of the effective conversion between fluorescence and heat in one CD system has rarely been ***,we provide a simple strategy for targeted microbial theranostics based on 4-carboxyphenylboronic acid-derived CDs(PCBA-CDs)which possess concentration-dependent photoluminescence/photothermal *** lower concentrations,PCBA-CDs show bright and stable fluorescent signals ranging from blue to *** fluorescence intensity gradually decreases with increasing concentration,while on the contrary,the photothermal effect of PCBA-CDs ascends progressively due to the rearrangement of electronic transitions in aggregated ***-CDs also demonstrate high affinity to the polysaccharide structures on the surface of microbe which allows rapid microbial fluorescence imaging as well as specific photothermal ablation of pathogens in skin wounds using PCBA-CDs at lower and higher concentrations,*** study supplies a facile nanotheranostic strategy for just-in-time microbial management using bioactive CDs.

关键词： Theranostic carbon dots Fluorescence imaging Phenylboronic acid Photothermal therapy Nanotheranostic

Performance Characterization of CR/PU Asphalt for Potential Application in Assembled Fast-Repairing Engineering

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Fluid Dynamics & Materials Processing 2024年第5期20卷 1063-1074页

作者： Hong Pang ao Lu Ming Xiong chen chen Xian Cao Xiong Xu Jing Wang Hubei Regional Management Headquarters CCCC Asset Management Co.Ltd.Beijing101399China School of Civil Engineering and Architecture Wuhan Institute of TechnologyWuhan430073China Hubei Provincial Engineering Research Center for Green Civil Engineering Materials and Structures Wuhan Institute of TechnologyWuhan430073China

Conventional repairing methods for asphalt pavement have some inconveniences,such as insufficient strength,and are typically *** address these issues,this study proposes a new technological method to design and prepare a high-performance assembled asphalt concrete block for fast repair of the potholes.A series of composite modified asphalt binders with 10%crumb rubber(CR)and different dosages(0%,1%,3%,5%)of polyurethane(PU)are examined to determine the optimized ***,the corresponding asphalt mixtures are prepared for further comparison and assessment of engineering properties,such as moistureinduced damage,high-temperature deformation,and low-temperature cracking *** test results show that PU can significantly improve the high-temperature performance and hardness of(crumb rubber modified asphalt)CRMA binder;3%PU contributes allowing the resistance of CRMA mixture to moisture-induced damage at higher levels,particularly under water whole immersion;as 3%PU is added,the high-temperature rutting deformation resistance of the CRMA mixture increases significantly,and the low-temperature anti-cracking properties are also improved ***,the innovatively designed high-quality assembled fast-repairing asphalt concrete block is recommended as an appropriate option for highway maintenance.

关键词： Composite modified asphalt crumb rubber polyurethane assembled fast-repairing asphalt concrete maintenance engineering

Defect-modulated and heteroatom-functionalized Ti_(3−x)C_(2)T_(y)MXene 3D nanocavities induce growth of MoSe_(2)nanoflakes toward electrocatalytic hydrogen evolution in all pH electrolytes

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Nano Research 2024年第7期17卷 6294-6304页

作者： Ming Du Xianzhi Yang Jian Zhang Wei chen Huajie Huang Xinbao Zhu Xing’ao Li State Key Laboratory for Organic Electronics and Information Displays and Institute of Advanced Materials(IAM) Jiangsu National Synergetic Innovation Centre for Advanced Materials(SICAM)Nanjing University of Posts and Telecommunications(NJUPT)Nanjing 210023China College of Electronic and Optical Engineering and College of Flexible Electronics Nanjing University of Posts and telecommunications(NJUPT) Nanjing 210023China New Energy technology Engineering Lab of Jiangsu Province College of ScienceNanjing University of Posts and Telecommunications(NJUPT)Nanjing 210023China College of Pharmaceutical and Chemical Engineering Taizhou UniversityJiaojiang 318000China College of Mechanics and Materials Hohai UniversityNanjing 210098China College of Chemical Engineering Nanjing Forestry UniversityNanjing 210037China

Reducing kinetic energy barriers and developing accessible active sites are critical to deliver high hydrogen evolution reaction(HER)*** this paper,we synthesized defect-modulated and heteroatom(boron)-functionalized three-dimensional(3D)bowl-shaped Ti_(3−x)C_(2)T_(y)MXene(B-TCT)nanocavities coupled with the vertical growth of MoSe_(2)*** B-TCT@MoSe_(2)nanohybrids catalyst delivers the overpotentials of 49.9,52.7,and 67.8 mV to reach a HER current density of 10 mA·cm^(−2)under acidic,alkaline,and neutral conditions,*** outstanding HER activity is predominantly attributed to the heteroatom functionalization,self-adapting Ti vacancy(VTi)defect modulation,and spatial configuration design in the 3D B-TCT nanocavity,which synergistically regulate the electronic structure,activate the basal plane/edge unsaturated sites,and reduce the reaction energy *** and theoretical calculations demonstrate that strong heterogeneous interfacial bonding interactions between B-TCT and MoSe_(2)can dramatically reduce the free energy of hydrogen adsorption and facilitate efficient interfacial charge migration,thus essentially improving the HER *** used this 3D porous nanohybrid system assembled by defectrich lamellar structures to elucidate the advantageous synergistic effects of multiple mechanisms among defect structure,heteroatom functionalization,and interfacial coupling,which provided important insights for the development of efficient hybridtype catalysts.

关键词： electrocatalytic H_(2)evolution three-dimensional(3D)MXene nanocavity MoSe_(2)nanoflake self-adapting Ti vacancy defect heteroatom-functionalized interfacial interaction