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Access to High-Molecular-Weight Polyethylenes through High Temperature Ethylene Polymerization Catalysed by Ethylene-Bridged ansa-(3-R-Cyclopentadienyl)(Fluorenyl) Zirconocene Complexes

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Chinese Journal of Polymer Science 2024年第1期42卷 42-51,I0007页

作者： bo li Haiyan ma Jiling Huang Shanghai Key Laboratory of Functional materials Chemistry and Laboratory of Organometallic Chemistry School of Chemistry and Molecular EngineeringEast China University of Science and TechnologyShanghai 200237China

A series of C1-symmetric ethylene-bridged ansa-(3-R-cyclopentadienyl)(fluorenyl) metallocene complexes(Zr: 1-5;Hf: 6) have been synthesized, characterized and investigated as catalyst precursors for the high temperature ethylene polymerization. Using methylaluminoxane(maO) as the cocatalyst, zirconium complexes 1-5 bearing a bulky substituent on the 3-position of the cyclopendienyl ring showed high catalytic activities up to 1.48×10^(7) g PE·mol_(Zr)^(-1)·h^(-1) toward the polymerization of ethylene and afforded polyethylenes with high molecular weights(1.49×10^(5)-6.31×10^(5) g/mol), meanwhile exhibting great thermal stability at high temperatures up to 120 ℃ together with a long catalytic life time up to 2 h. By adopting low Al/Zr ratios, such as 125, polyethylenes with ultra high molecular weights up to 2.86×106 g/mol were obtained. It is worthy of noting that zirconium complexes 1-4 bearing a substituent with an aryl pendant showed temperature-dependent activities, which increased rapidly with the increase of polymerization temperature, thus weak interaction of the pendent aryl group with the cationic active center is proposed to account for the very low activities displayed at low temperatures. In contrast to zirconocene complexes 1-5, hafnocene complex 6 only displayed very low catalytic activities toward the polymerization of ethylene and afforded polyethylenes with molecular weights ten times smaller than those obtained by zirconocene complexes 1-5. Zirconocene complexes 1-5 were also able to catalyse the polymerization of propylene at high temperatures, but only afforded waxes with low molecular weights.

关键词： ansa-Metallocene Ethylene Propylene Polymerization High temperature

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Detecting the distribution of and public attitudes to charismatic alien species based on media coverage

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Avian Research 2024年第3期15卷 379-384页

作者： Yuexuan liu Ruichang Sun bo li Zhijun ma Shanghai Institute of Infectious Disease and Biosecurity Ministry of Education Key Laboratory for Biodiversity Science and Ecological EngineeringNational Observations and Research Station for Wetland Ecosystems of the Yangtze Estuaryand Institute of Eco-Chongming(SIEC)School of Life SciencesFudan UniversityShanghai200433China Yunnan Key Laboratory of Plant Reproductive Adaptation and Evolutionary Ecology and Centre for Invasion Biology Institute of BiodiversitySchool of Ecology and Environmental ScienceYunnan UniversityKunming650504YunnanChina

Charismatic species are often reported by the media,providing information for detecting population status and public *** identify the number and distribution of free-living Black Swan(Cygnus atratus),a charismatic alien species in Chinese mainland and to detect the public and the media attitudes to the species,we analyzed the reports and emotional tendency from media coverage in 2000-2022 using manual reading,crawler extraction and latent Dirichlet allocation.A total of 6654 Black Swans were reported at 711 sites,including 147 individuals at 30 nature *** breeding was reported at one-fourth of the total sites,including five nature *** proportion of positive emotional tendency to Black Swans was overwhelming in the reports and was higher than that to alien species in general,suggesting that the public and the media are unaware of the risk of biological *** management of invasive species requires the media clarifies the invasion risk of charismatic alien *** the unity between the harmfulness of abstract concept of alien species and the charisma of a specific alien species among the public help effective management.

关键词： Alien species Biological invasion Cygnus atratus Emotional tendency Invasive species Media coverage Public perception

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A Multi-Token Sector Antenna Neighbor Discovery Protocol for Directional Ad Hoc Networks

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China Communications 2024年第7期21卷 149-168页

作者： Zhang Hang li bo yan Zhongjiang yang mao li Xinru School of Electronics and Information Northwestern Polytechnical UniversityXi’an 710072China The 54th Research Institute of CETC Shijiazhuang 050081China

In this paper,we propose a Multi-token Sector Antenna Neighbor Discovery(M-SAND)protocol to enhance the efficiency of neighbor discovery in asynchronous directional ad hoc *** central concept of our work involves maintaining multiple tokens across the *** prevent mutual interference among multi-token holders,we introduce the time and space non-interference ***,we propose a master-slave strategy between *** the master token holder(MTH)performs the neighbor discovery,it decides which 1-hop neighbor is the next MTH and which 2-hop neighbors can be the new slave token holders(STHs).Using this approach,the MTH and multiple STHs can simultaneously discover their neighbors without causing interference with each *** on this foundation,we provide a comprehensive procedure for the M-SAND *** also conduct theoretical analyses on the maximum number of STHs and the lower bound of multi-token generation ***,simulation results demonstrate the time efficiency of the M-SAND *** compared to the QSAND protocol,which uses only one token,the total neighbor discovery time is reduced by 28% when 6beams and 112 nodes are employed.

关键词： multi-token neighbor discovery SAND protocol sector antenna ad hoc network

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Achieving strength-ductility synergy in novel paramagnetic Fe-based medium-entropy alloys through deep cryogenic deformation

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Rare Metals 2024年第9期43卷 4493-4507页

作者： Hu-Wen ma.yan-Chun Zhao li Feng Tian-Zeng liu Zhi-Qi Yu bo Jin Wang-Chun Duan Peter K.liaw Dong ma State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals Lanzhou University of TechnologyLanzhou 730050China Wenzhou Pump and Valve Engineering Research Institute Lanzhou University of TechnologyWenzhou 325105China Iron and Steel Research Institute Jiuquan Iron and Steel CorporationJiayuguan 735100China Lanzhou Resources and Environment Voc-Tech University Lanzhou 730123China Department of materials Science and Engineering The University of TennesseeKnoxvilleTN 37996-2200USA Neutron Science Center Songshan Lake Materials LaboratoryDongguan 523808China

Cryogenic pre-deformation treatment has been widely used to effectively improve the comprehensive mechanical properties of steels and novel ***,the dislocation evolution and phase transformation induced by different degrees of deep cryogenic deformation are not yet fully *** this study,the effects of multiple cryogenic pre-treatments on the mechanical properties and deformation mechanisms of a paramagnetic Fe_(63.3)Mn_(14-)Si_(9.1)Cr_(9.8)C_(3.8)medium-entropy alloy(MEA)were investigated,leading to the discovery of a pretreated MEA that exhibits exceptional mechanical properties,including a fracture strength of 3.0 GPa,plastic strain of 26.1%and work-hardening index of *** addition,X-ray diffraction(XRD)and transmission electron microscopy(TEM)analyses revealed that multiple cryogenic pre-deformation treatments significantly increased the dislocation density of the MEA(from 9×10^(15)to 4×10^(16)m^(-2)after three pretreatments),along with a transition in the dislocation type from predominantly edge dislocations to mixed dislocations(including screw-and edge-type dislocations).Notably,this pretreated MEA retained its paramagnetic properties(μ_(r)mately four(i.e.,from 9.7 to2.6 m J·m^(-2)),thereby activating the synergistic effects of transformation-induced plasticity,twinning-induced plasticity and dislocation strengthening *** synergistic effects lead to simultaneous strength and ductility enhancement of the MEA.

关键词： Deep cryogenic transformation Iron-based medium-entropy alloys Dislocation evolution Phase transformation Stacking fault energy

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magneto-optical isotope enrichment of potassium-40 with transverse cooling

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Chinese Optics Letters 2024年第7期22卷 1-5页

作者： Shangjin li Zixuan Zeng bo yan School of Physics Zhejiang UniversityHangzhou 310027China

Isotope shifts among different isotopes can be effectively addressed using narrow-linewidth lasers,facilitating laser isotope separation and achieving significant enrichment at a single *** separation of potassium isotopes,employing optical pumping and magnetic deflection,has proven to be *** further improve the enrichment of ^(40)K,we introduce 2D transverse cooling to minimize the divergence *** this modification,we demonstrate enrichment of ^(40)K,elevating it from 0.012%to 12%–20%.This represents an enrichment increase by three orders of magnitude,surpassing our previous result by one *** method is particularly well-suited for isotope enrichment of elements with extremely low abundance.

关键词： isotope separation potassium isotopes two-dimensional transverse cooling

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Scenarios analysis and performance assessment of blockchain integrated in 6G scenarios

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Science China(Information Sciences) 2024年第7期67卷 5-26页

作者： bo li Guanjie CHENG Honghao GAO Xueqiang yan Shuiguang DENG College of Computer Science and Technology Zhejiang University College of Computer Science and Technology Shanghai University 2012 Lab Huawei Technologies Co. Ltd.

Emerging applications such as smart city infrastructures and virtual reality landscapes are setting rigorous benchmarks for 6G mobile networks, requiring elevated levels of confidentiality, integrity, nonrepudiation, authentication, and stringent access controls. Blockchain technology is heralded as a transformative enabler for meeting 6G standards, owing to its intrinsic attributes. However, a gap exists in the holistic investigation of blockchain's applicability in 6G realms, particularly addressing the “whether”, “when”, and“how” of its deployment. Present research trails in developing robust methodologies to gauge blockchain's efficacy within 6G use cases. Addressing this, our study introduces a novel confluence of blockchain with 6G networks, where data resides in distributed Hash tables(DHTs) while their hashes are secured in distributed ledger technology(DLT), harnessing blockchain's core strengths-immutability, traceability, and fortified security. We delineate seven specific 6G use cases poised for enhancement through blockchain integration,and scrutinize the rationale, nature, and timing of this convergence. Furthermore, we devise a comprehensive methodology for assessing blockchain's performance metrics and scalability in 6G environments. Our extensive experimental analyses evaluate the synergistic performance of this integration, revealing that the Quorum blockchain satisfactorily supports 80% of 6G scenarios. The findings suggest that, with appropriate configurations, consortium blockchains are well-equipped to fulfill the demanding performance and scalability requisites of 6G networks.

关键词： blockchain distributed ledger technology (DLT) 6G performance assessment 6G scenarios analysis transaction arrival rate

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JudPriNet: Video transition detection based on semantic relationship and Monte Carlo sampling

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Intelligent and Converged Networks 2024年第2期5卷 134-146页

作者： bo ma Jinsong Wu Wei Qi yan School of Engineering Computer and Mathematical SciencesAuckland University of TechnologyAuckland 1024New Zealand School of Artificial Intelligence Guilin University of Electronic TechnologyGuilin 540004Chinaand also with the Department of Electrical EngineeringUniversity of ChileSantiago 8010037Chile

Video understanding and content boundary detection are vital stages in video ***,previous content boundary detection methods require collecting information,including location,cast,action,and audio,and if any of these elements are missing,the results may be adversely *** address this issue and effectively detect transitions in video content,in this paper,we introduce a video classification and boundary detection method named *** focus of this paper is on objects in videos along with their labels,enabling automatic scene detection in video clips and establishing semantic connections among local objects in the *** a significant contribution,JudPriNet presents a framework that maps labels to“Continuous Bag of Visual Words Model”to cluster labels and generates new standardized labels as video-type *** facilitates automatic classification of video ***,JudPriNet employs Monte Carlo sampling method to classify video clips,the features of video clips as elements within the *** proposed method seamlessly integrates video and textual components without compromising training and inference *** experimentation,we have demonstrated that JudPriNet,with its semantic connections,is able to effectively classify videos alongside textual *** results indicate that,compared with several other detection approaches,JudPriNet excels in high-level content detection without disrupting the integrity of the video content,outperforming existing methods.

关键词： video scene detection Monte Carlo object detection Continuous Bag-of-Words

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Influence of friction-lubrication characteristics varying with rolling speed on instability of chatter and slip in cold tandem rolling process

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Journal of Iron and Steel Research International 2024年第4期31卷 894-908页

作者： yan-li Xin Zhi-ying Gao bo Tian Qing-dong Zhang School of Mechanical Engineering University of Science and Technology BeijingBeijing 100083China

In the high-speed cold tandem rolling process of thin plate,chatter or slip instability gives rise to the deterioration of equipment and product *** instability behavior is closely related to interfacial friction-lubrication con-dition which is generally characterized by the friction ***,with higher and higher speed requirements,the commonly used model of friction coefficient is no longer applicable and accurate.A novel approach is suggested to calculate the speed-dependent friction coefficient,in which the viscosity-pressure-temperature effects of the lubricant,surface roughness states of work rolls and rolled piece are comprehensively involved and the mixed flm lubrication theory is ***,the influences of friction coefficient on the instability of slip and chatter are investigated for a five-stand cold tandem rolling *** one side,the critical friction coefficient for each stand is determined by calculating the corresponding slip factor;on the other hand,the friction coefficient varying with rolling speed is combined with the model of theoretical critical rolling speed presented under constant friction coefficient,so that the speed threshold is ***,the stable and unstable regions corresponding to the rear three stands are individually discussed,and the technical strategies are proposed to suppress both slip and chatter frequently occurring in the actual rolling process.

关键词： Cold tandem rolling:Oil film thickness Speed-dependent friction coefficient-Slip:Chatter

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UiO-66-NH_(2)nanoparticles supported on layered double hydroxides as an excellent adsorbent for levofloxacin capture

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Particuology 2024年第9期92卷 155-165页

作者： yan li Heng lin Qiaolan Yu Na ma Wei Dai College of Geography and Environmental Sciences Zhejiang Normal UniversityJinhua321004China Key Laboratory of the Ministry of Education for Advanced Catalysis materials College of Chemistry and Materials ScienceZhejiang Normal UniversityJinhua321004China

The adsorption performances of individual adsorbent such as UiO-66-NH_(2)and MgAl-layered double hydroxides(MgAl-LDH)toward levofloxacin(LVX)is less satisfactory due to the disappointing uptake capacity and adsorption ***,a 3D flower-like composite adsorbent prepared via iterative hydrothermal synthesis method anchoring UiO-66-NH_(2)nanoparticles onto the MgAl-LDH *** to the synergistic effects of UiO-66-NH_(2),and MgAl-LDH,the MgAl-LDH@UiO-66-NH_(2)exhibits an outstanding adsorption performance toward ***,the maximum LVX uptake capacity over MgAl-LDH@UiO-66-NH_(2)reached 268 mg/g,which was higher than that of the individual adsorption materials UiO-66-NH_(2)(41 mg/g),MgAl-LDH(140 mg/g),and some adsorbents reported in previous *** rapid adsorption process can reach equilibrium within 20 min,which conformed well to the pseudo-second-order kinetics and the Langmuir isotherm *** thermodynamic result also indicated that the adsorption was spontaneous and exothermic,simultaneous coexisting physical and chemical adsorption ***,the MgAl-LDH@UiO-66-NH_(2)still maintained excellent adsorption capacity with a slightly decrease after fifth cycle,exhibiting a remarkable reuse and stable *** work provides a highly novel strategy to prepare recyclable composite adsorbent for the LVX capture from aqueous solution.

关键词： Layered double hydroxides UiO-66-NH_(2) LVX Adsorption

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Experimental Investigation on Solution Regeneration Performance and Coefficients in Full-Open System for Heat and Water Recovery of Flue Gas

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Journal of Thermal Science 2024年第3期33卷 1094-1108页

作者： WEI Hongyang HUANG Shifang ma Yuxin CHEN bo SUN li ZHANG Xiaosong School of Energy and Environment Southeast UniversityNanjing210096China MOE Engineering Research Center for Building Energy Equipment&Environment Southeast UniversityNanjing210096China Jiangsu Frontier Electric Technology Co. LtdNanjing211106China

The recovery of heat and water from low-grade flue gas is of considerable importance for energy conservation and environmental *** the full-open absorption heat pump shows promise as a means of achieving heat and water recovery,the lack of research on heat and mass transfer performance of open-type solution evaporation regeneration represents a significant impediment to its design and *** paper experimentally investigates the regeneration performance of an open-type spaying tower equipped with ceramic structured *** different regeneration modes are proposed,namely ambient air receiver mode and flue gas receiver mode,to utilize air or low-grade flue gas as a driving *** impact of different input parameters on the regeneration characteristics,including heat transfer capacity,water removal rate,thermal efficiency,and humidity effectiveness,are *** findings indicate that the enhancement of regeneration can be achieved through the increase of solution flow rate,solution temperature,and flue gas flow rate in both regeneration ***,high solution concentration and flue gas humidity ratio can weaken water removal rates and reduce thermal *** the regeneration of CaCl_(2)-H_(2)O with a concentration of55%,flue gas around 200℃with a humidity ratio below 44 g/kg can successfully drive the solution regeneration *** the solution concentration or flue gas humidity ratio continues to rise,additional energy is necessary for ***,the coupled heat and mass transfer coefficients are fitted,which can contribute to the design and optimization of the open-type regenerator.

关键词： heat and water recovery solution regeneration flue gas regeneration performance coefficient

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