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Melting Temperature of Individual Electrospun Poly(vinylidene fluoride) Fibers Studied by AFM-based Local Thermal Analysis

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Chinese Journal of Polymer Science 2021年第2期39卷 219-227,I0007页

作者： ze-qian wang Zhen-Xing Zhong Yu-Ying Ma Xiao-Feng Lu Ce wang Zhao-Hui Su State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China University of Science and Technology of China Hefei 230026China Alan G.MacDiarmid Institute Jilin UniversityChangchun 130012China

Thermal properties such as melting temperature can well reflect the microstructure of the polymer material, and have practical implications in the application of nanofibers. In this work, we investigated the melting temperature of individual electrospun poly(vinylidene fluoride)(PVDF) nanofibers with diameters ranging from smaller than 200 nm to greater than 2 μm by the local thermal analysis technique. The PVDF fibers obtained under four different conditions were found to crystallize into α and β phases, and the fiber mats showed typical values in the crystallinity and Tm with no significant difference among the four. However, analyses at single fiber level revealed broad distribution in diameter and Tm for the fibers produced under identical electrospinning condition. The Tm of individual nanofibers was found to remain constant at large diameters and increase quickly when reducing the fiber diameter toward the nanoscale, and Tm values of 220-230 ℃ were observed for the thinnest nanofibers, much higher than the typical values reported for bulk PVDF. The Tm and molecular orientation at different positions along a beaded fiber were analyzed, showing a similar distribution pattern with a minimum at the bead center and higher values when moving toward both directions. The results indicate that molecular orientation is the driving mechanism for the observed correlation between the Tm and the diameter of the nanofibers.

关键词： Electrospun fibers PVDF Local thermal analysis Melting temperature

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Self-nucleation of Patterned Polymer Thin Films Defined by Soft Lithography

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Chinese Journal of Polymer Science 2022年第6期40卷 651-657页

作者： ze-qian wang Yi-Meng wang Xing-Yu wang Bing-Hua wang Jing-Bo Chen Chang-Yu Shen Bin Zhang School of Materials Science&Engineering Zhengzhou UniversityZhengzhou 450002China

The nucleation of crystals is often a determining step in the phase transition of materials,but it remains a challenge to control the density and specific location of nuclei *** we fabricated the isolated single crystals of uniform size with controlled number density and spatial distribution by self-nucleation of patterned dendritic *** lithography creates the periodic void space on the surface of poly(ethylene oxide)-b-poly(2-vinyl pyridine)(PEO-b-P2VP)block copolymer thin films and provides spatial redistribution of polymers,leading to the preferential nucleation and subsequent oriented growth of dendrites in the periodic arrays of imprinted *** morphology and thermal stability of the patterned crystals can be adjusted by tuning embossing conditions(e.g.,temperature and pressure).Furthermore,in the self-nucleation technique,the annealing temperature and heating rate are used as the feedback parameters to map the number density and spatial distribution of regrown single *** PEO-b-P2VP crystalline pattern can be used as a versatile template for large-area manufacturing of selective metal patterns for electronic devices and other applications.

关键词： Self-nucleation Imprint lithography Atomic force microscopy Crystallization pattern Selective metal pattern

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Robustness of the octupole collectivity in 144Ba within the cranking covariant density functional theory in 3D lattice

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Nuclear Science and Techniques 2024年第8期35卷 124-131页

作者： ze‑Kai Li Yuan‑Yuan wang Mathematics and Physics Department North China Electric Power UniversityBeijing 102206China Hebei Key Laboratory of Physics and Energy Technology North China Electric Power UniversityBaoding 071000China

The octupole deformation and collectivity in octupole double-magic nucleus 144Ba are investigated using the Cranking covariant density functional theory in a three-dimensional lattice *** reduced B(E3)transition probability is implemented for the first time in semiclassical approximation based on the microscopically calculated electric octupole *** available data,including the I-ωrelation and electric transitional probabilities B(E2)and B(E3)are well ***,it is shown that the ground state of 144Ba exhibits axial octupole and quadrupole deformations that persist up to high spins(I≈24h).

关键词： Octupole collectivity Cranking covariant density functional theory Rotational spectrum Electric transitional probabilities

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One-pot Synthesis of Hierarchical Flower-like WS_(2) Microspheres as Anode Materials for Lithium-ion Batteries

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Journal of Wuhan University of Technology(Materials Science) 2024年第1期39卷 1-6页

作者：张向华 TAN Hen wang ze XUE Maoquan School of Mechanical Engineering Jiangsu University of TechnologyChangzhou 213001China School of Materials Engineering Jiangsu University of TechnologyChangzhou 213001China Changzhou Vocational Institute of Industry Technology Changzhou 213164China

3D hierarchical flowerlike WS_(2) microspheres were synthesized through a facile one-pot hydrothermal *** as-synthesized samples were characterized by powder X-ray powder diffraction (XRD),energy-dispersive spectroscopy (EDS),scanning electron microscopy (SEM) and *** images of the samples reveal that the hierarchical flowerlike WS_(2) microspheres with diameters of about 3-5μm are composed of a number of curled *** tests such as charge/discharge,cyclic voltammetry,cycle life and rate performance were carried out on the WS_(2) *** an anode material for lithium-ion batteries,hierarchical flowerlike WS_(2) microspheres show excellent electrochemical *** a current density of100 mA·g^(-1),a high specific capacity of 647.8 mA·h·g^(-1) was achieved after 120 discharge/charge *** excellent electrochemical performance of WS_(2) as an anode material for lithium-ion batteries can be attributed to its special 3D hierarchical structure.

关键词： WS_(2) microspheres lithium-ion batteries electrochemical performance

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Spatial Distribution Pattern and Influencing Factors of Bed-and-breakfasts(B&Bs)from the Perspective of Urban-rural Differences:A Case Study of Jiaodong Peninsula,China

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Chinese Geographical Science 2024年第4期34卷 752-763页

作者： wang Xinyue MA qian Management College Ocean University of ChinaQingdao 266100China

There are significant differences between urban and rural bed-and-breakfasts(B&Bs)in terms of customer positioning,economic strength and spatial *** identifying the differences in spatial characteristics and influencing factors of each type,is essential for creating urban and rural B&B agglomeration *** study used density-based spatial clustering of applications with noise(DBSCAN)and the multi-scale geographically weighted regression(MGWR)model to explore similarities and differences in the spatial distribution patterns and influencing factors for urban and rural B&Bs on the Jiaodong Peninsula of China from 2010 to *** results showed that:1)both urban and rural B&Bs in Jiaodong Peninsula went through three stages:a slow start from 2010 to 2015,rapid development from 2015 to 2019,and hindered development from 2019 to ***,urban B&Bs demonstrated a higher development speed and agglomeration intensity,leading to an increasingly evident trend of uneven development between the two sectors.2)The clustering scale of both urban and rural B&Bs continued to expand in terms of quantity and *** B&B clusters characterized by a limited number,but a higher likelihood of transitioning from low-level to high-level *** the number of rural B&B clusters steadily increased over time,their clustering scale was comparatively lower than that of urban B&Bs,and they lacked the presence of high-level clustering.3)In terms of development direction,urban B&B clusters exhibited a relatively stable pattern and evolved into high-level clustering centers within the main urban ***,rural B&Bs exhibited a more pronounced spatial diffusion effect,with clusters showing a trend of multi-center development along the coastline.4)Transport emerged as a common influencing factor for both urban and rural B&Bs,with the density of road network having the strongest explanatory power for their spatial *** terms of differences,populati

关键词： urban-rural bed-and-breakfasts(B&Bs) spatiotemporal evolution density-based spatial clustering of applications with noise(DBSCAN)model multi-scale geographically weighted regression(MGWR) Jiaodong Peninsula China

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BLS-identification:A device fingerprint classification mechanism based on broad learning for Internet of Things

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Digital Communications and Networks 2024年第3期10卷 728-739页

作者： Yu Zhang Bei Gong qian wang Faculty of Information Technology Beijing University of TechnologyBeijing100124China School of Information Science and Technology Zhengzhou Normal UniversityHenan450044China

The popularity of the Internet of Things(IoT)has enabled a large number of vulnerable devices to connect to the Internet,bringing huge security *** a network-level security authentication method,device fingerprint based on machine learning has attracted considerable attention because it can detect vulnerable devices in complex and heterogeneous access ***,flexible and diversified IoT devices with limited resources increase dif-ficulty of the device fingerprint authentication method executed in IoT,because it needs to retrain the model network to deal with incremental features or *** address this problem,a device fingerprinting mechanism based on a Broad Learning System(BLS)is proposed in this *** mechanism firstly characterizes IoT devices by traffic analysis based on the identifiable differences of the traffic data of IoT devices,and extracts feature parameters of the traffic packets.A hierarchical hybrid sampling method is designed at the preprocessing phase to improve the imbalanced data distribution and reconstruct the fingerprint *** complexity of the dataset is reduced using Principal Component Analysis(PCA)and the device type is identified by training weights using *** experimental results show that the proposed method can achieve state-of-the-art accuracy and spend less training time than other existing methods.

关键词： Device fingerprint Traffic analysis Class imbalance Broad learning system Access authentication

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Injection molding of highly filled microcrystalline cellulose/polycaprolactone composites with the aid of reversible Diels-Alder reaction

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Journal of Materials Science & Technology 2024年第3期170卷 246-254页

作者： ze Pu wang WenHong Ruan MinZhi Rong MingQiu Zhang Key Laboratory for Polymeric Composite and Functional Materials of MOE GD HPPC LabIGCMESchool of ChemistrySun Yat-Sen UniversityGuangzhou 510275China

To tackle the challenge of producing highly filled polymer composites using the traditional injection molding technique,which is characterized by the fairly high melt viscosity that makes mold filling difficult,the authors propose a solution based on dynamic covalent *** demonstrated by the proof-of-concept experiments,the 4-arm starshaped polycaprolactone(PCL)oligomers and microcrystalline cel-lulose(MCC)are crosslinked by the reversible Diels-Alder(DA)*** flowability of the compounds greatly decreases due to the dissociation of the intercomponent DA bonds at the retro-reaction tempera-ture,and the networked architecture is reconstructed during cooling as a result of the forward DA ***,the high-loading MCC fillers are well distributed in the matrix and covalently bonded to the nearby PCL,forming a striking contrast to the control in which linear PCL acts as the *** DA bonds crosslinked biodegradable PCL composites exhibit decent mechanical strength(20.7 MPa)even at the MCC fraction of 65 wt%,which is superior to those(5-12.2 MPa)of the highly filled PCL composites(with filler contents of 50-63.8 wt%)reported so *** proposed approach has sufficient expansibility for the fabrication of the highly filled polymer composites constructed by other types of matrix and fillers.

关键词： Polymer composites Microcrystalline cellulose Polycaprolactone Injection molding Dynamic reversible chemistry

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Melt flow,heat transfer and solidification in a flexible thin slab continuous casting mold with vertical-combined electromagnetic braking

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Journal of Iron and Steel Research International 2024年第2期31卷 401-415页

作者： Lin Xu ze-feng Han Christian Karcher En-gang wang Key Laboratory of Electromagnetic Processing of Materials(Ministry of Education) Northeastern UniversityShenyang110819LiaoningChina Key Laboratory of Liaoning Province for Clean Combustion Power Generation and Heating Technology Shenyang Institute of EngineeringShenyang110136LiaoningChina Institute of Thermodynamics and Fluid Mechanics Technische Universität IlmenauIlmenau98684Germany

During continuous casting of steel slabs,the application of electromagnetic braking technology(EMBr)provides an effective tool to influence solidification by controlling the pattern of melt flow in the ***,the quality of the final product can be improved considerably.A new electromagnetic braking(EMBr)method,named vertical-combined electromagnetic braking(VC-EMBr),is proposed to be applied to a flexible thin slab casting(FTSC)*** evaluate the beneficial effects of the VC-EMBr,the melt flow,heat transfer,and solidification processes in the FTSC mold are studied by means of numerical *** detail,a Reynolds-averaged Navier–Stokes turbulence model together with an enthalpy-porosity approach was *** numerical findings are compared with respective simulations using the traditional *** results demonstrate that the application of the VC-EMBr contributes significantly to preventing relative slab *** contrast to the Ruler-EMBr,the additional vertical magnetic poles of the VC-EMBr preferentially suppress the direct impact of jet flow on the narrow face of FSTC mold and considerably diminish the level fluctuation near the meniscus *** instance,by applying a magnetic flux density of 0.3 T,the maximum amplitude of meniscus deflection reduces by about 80%.Moreover,the braking effect of the VC-EMBr effectively improves the homogeneity of temperature distribution in the upper recirculation region and increases the solidified shell thickness along the casting *** this basis,the newly proposed VC-EMBr shows a beneficial effect in preventing relative slab defects for FTSC thin slab continuous casting.

关键词： Electromagnetic braking Mold Melt flow Heat transfer Solidification

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Investigation of Maxima Assumptions in Modelling Tropical Cyclone- Induced Hazards in the South China Sea

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China Ocean Engineering 2024年第3期38卷 491-504页

作者： WEN ze-guo wang Fu-ming WAN Jing YANG Fan School of Civil Engineering Sun Yat-sen University&Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Zhuhai 519082China Guangdong Academy of Safety Science and Technology Guangzhou 510060China Guangdong Key Laboratory of Oceanic Civil Engineering Guangzhou 510275China Advanced Energy Science and Technology Guangdong Laboratory(Yangjiang Offshore Wind Energy Laboratory) Yangjiang 529500China

The present study aims to examine the suitability of two commonly used assumptions that simplify modelling metoceanconditions for designing offshore wind turbines in the South China Sea (SCS). The first assumption assumes thatjoint N-year extreme wind and wave events can be independently estimated and subsequently combined. The secondone assumes peak wind and waves can be modelled as occurring simultaneously during a tropical cyclone (TC) *** better understand the potential TC activity, a set of 10000 years synthetic TC events are generated. The wind fieldmodel and the Mike 21 spectral wave model are employed to model the TC-induced hazards. Subsequently, theeffect of the assumptions is evaluated by analyzing the peak structural response of both monopile and semisubmersibleoffshore wind turbines during TC events. The results demonstrate that the examined assumptions are generally *** assessing the implications of these assumptions, valuable insights are obtained, which can inform andimprove the modelling of TC-induced hazards in the SCS region.

关键词： tropical cyclone numerical wave modelling hazards offshore wind turbines structural response

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Molecular Mechanism of Rice Necrotic Lesion for Optimized Yield and Disease Resistance

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Rice science 2024年第3期31卷 285-299页

作者： HOU Xinyue wang Yuping qian qian REN Deyong State Key Laboratory of Rice Biology and Breeding China National Rice Research InstituteHangzhou 310006China State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China Rice Research InstituteSichuan Agricultural UniversityChengdu 611130China

How to balance rice resistance and yield is an important issue in rice *** with mutated necrotic lesion genes often have persistent broad-spectrum resistance,but this broad-spectrum resistance usually comes at the expense of ***,many necrotic lesion mutants in rice have been identified,and these genes are involved in disease resistance *** review provides a detailed introduction to the characteristics,classification,and molecular mechanisms of necrotic lesion ***,we review the molecular regulatory pathways of genes involved in rice disease ***,we summarize the relationship between resistance and yield in rice using newly developed gene editing *** discuss a rational and precise breeding strategy to better utilize molecular design technology for breeding disease-resistant and high-yield rice varieties.

关键词： rice necrotic lesion regulation mechanism high yield high resistance

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