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Polarization-driven multifunctional organohydrogels with strain sensitivity toward electromagnetic wave absorption

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Nano Research 2024年第6期17卷 5688-5697页

作者： yunfei zhang Lei zhang Bingqian Zhou Yishan Gao Baoliang zhang School of Chemistry and Chemical Engineering Northwestern Polytechnical UniversityXi’an 710072China Shaanxi Engineering and Research Center for Functional Polymers on Adsorption and Separation Sunresins New Materials Co.Ltd.Xi’an 710072China

Rapid advancements in flexible electronics and military applications necessitate high-performance electromagnetic wave(EMW)*** huge breakthroughs in achieving high-attenuation microwave absorption,conventional EMW absorbing materials have single function and ambiguous absorption ***,numerous gel-type absorbers are fabricated by introducing“regulators”into poly(acrylamide-co-acrylic acid)(P(AM-co-AA))networks through radical polymerization in a glycerol-water mixed *** dielectric constant and EMW absorption performance of the gels are precisely predicted by adjusting monomer concentration,the ratio of glycerol/water,and the content of the ***,A_(6)G_(20)T_(20)-2 exhibits promising absorption performance with a minimum reflection loss(RL_(min))of-33.8 dB at 12.4 *** effective absorption bandwidth(EAB)covers the entire X-band(8.2-12.4 GHz)at a thickness of 2.7 mm.A_(6)G_(20)T_(20)-2 also has sensitive deformation responses and excellent tensile strength,adhesiveness,self-healing and anti-freezing ***,this work not only provides insight into the polarization loss mechanism of the gels as the result of high correlation between EMW absorbing properties and molecular polarization,but also offers an important reference for developing functional protective materials because of the rich functionalities and efficient protective capabilities of the gels.

关键词： organohydrogels molecular polarization microwave absorption strain sensor

Differential game-based analysis of multi-attacker multi-defender interaction

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Science China(Information Sciences) 2021年第12期64卷 202-214页

作者： Qiuyue GAO Huici WU yunfei zhang Xiaofeng TAO National Engineering Laboratory for Mobile Network Technologies Beijing University of Posts and Telecommunications

Due to the increasing number of wireless terminals and progressively extensive interconnections among them, interaction between the attack group and defense group is becoming a dominant security manifestation in future wireless networks. This paper focuses on the modeling and analysis of multi-attacker to multi-defender interaction. First, considering the continuous interaction between the attack group and defense group in real-time, a differential game-based multi-attacker to multi-defender interaction model is explicated with paralysis threshold introduced to reduce the ping-pong effect in paralysis. Optimal control theory is then introduced to obtain the equilibrium strategy with Hamilton best control method and a proposed optimal strategy selection algorithm for multi-attacker to multi-defender interaction. Finally, simulations are provided to demonstrate the evolutionary trajectory of optimal attack and defensive strategies and the relationship between the paralysis threshold and the group strength evolution results. Numerical results show the attackers and defenders are aggressive to strengthen their groups initially and then gradually decrease their strength to obtain ideal cost-effectiveness ratios. Moreover, increasing the defense paralysis threshold within a certain range will be more conducive to improving the defense effectiveness.

关键词： differential game multi-attacker to multi-defender interaction optimal control theory Hamilton function equilibrium strategy

Core-shell structured Co@NC@MoS_(2)magnetic hierarchical nanotubes:Preparation and microwave absorbing properties

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Journal of Materials Science & Technology 2022年第33期128卷 148-159页

作者： yunfei zhang Yulong Li Mengmeng Wei Dengtao Yang Qiuyu zhang Baoliang zhang School of Chemistry and Chemical Engineering Northwestern Polytechnical UniversityXi’an 710072China Xi’an Key Laboratory of Functional Organic Porous Materials Northwestern Polytechnical UniversityXi’an 710129China Shaanxi Engineering and Research Center for Functional Polymers on Adsorption and Separation Sunresins New Materials Co.Ltd.Xi’an 710072China

In this study,a new lightweight one-dimensional absorber Co@NC@MoS_(2)was designed and ***,polydopamine(PDA)was coated by oxidative self-polymerization with cobalt-nitrilotriacetic acid chelate nanowires(Co-NTAC)as *** core-shell structured magnetic hierarchical nanotubes(Co@PDA@MoS_(2))were prepared by one-step hydrothermal *** thermal annealing,PDA layer was transformed into nitrogen doped carbon layer(NC)to obtain the efficient microwave absorber Co@NC@MoS_(2).The removal of template and growth of MoS_(2)were completed simultaneously,the preparation process was *** of its good magnetic loss and dielectric loss,Co@NC@MoS_(2)shows excellent microwave absorption *** filler content of 15 wt.%,the minimum reflection loss(RL_(min))can reach-61.97 dB@9.2 GHz,and the effective absorption bandwidth(EAB)is 5.6 *** electromagnetic parameters of Co@NC@MoS_(2)can be further adjusted by changing the load of MoS_(2).Meanwhile,the structure and composition of Co@NC@MoS_(2)were systematically *** influence of the microstructure on the microwave absorbing properties was investigated,and the microwave attenuation mechanism is *** an efficient and lightweight absorber,Co@NC@MoS_(2)has potential application value in the construction of new stealth coatings.

关键词： Nanotubes Magnetic materials Core-shell structure MoS_(2)nanosheets Electromagnetic wave absorption

Molecular dynamics study of water molecules nucleation for fine particle removal:Effects of wettability and aggregation modes and comparison with experiment Author links open overlay panel

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Particuology 2024年第8期91卷 106-117页

作者： Junchao Xu Zhipeng zhang Li Lv yunfei zhang Yiming Xie Huaqiang Chu School of Energy and Environment Anhui University of TechnologyMaanshan243002China College of Mechanical and Electrical Engineering China Jiliang UniversityHangzhou310018China

Water vapor nucleation on particle's surface plays an important role in dust removal,cloud formation,and particle ***,the selectivity of nucleation sites and the nucleation characteristic of water molecule on the particle's surface are still unclear,especially for the aggregated *** this paper,the effects of particle wettability and aggregation modes on the selectivity of nucleation sites and the nucleation characteristics were investigated using molecular dynamics *** results were compared with our earlier experimental *** illustrates how the contact angle of clusters,the growth velocity,and the growth duration are all influenced by the interaction coefficient between water and ***,the nucleation sites of water molecules on the particle aggregation surface exhibit a definite *** primary indicator of this selectivity is the preferential nucleation of water molecules at the interfaces of linear chain aggregation particles,at the inner side of non-linear chain aggregation particles,and at the centers of ring *** results are in good agreement with our previous experimental *** significantly,additional research has revealed that subcritical-size clusters typically aggregate on two-particle surfaces spacing when the spacing smaller than the critical cluster size.

关键词： Heterogeneous nucleation Water molecule Wettability Aggregation modes Molecule dynamics

Liquid-phase hydrodechlorination of trichloroethylene driven by nascent H_(2)under an open system:Hydrogenation activity,solvent effect and sulfur poisoning

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Journal of Environmental Sciences 2021年第10期33卷 96-106页

作者： Weilai Wang Fan zhang yunfei zhang Lei Xu Yuansheng Pei Junfeng Niu State Key Laboratory of Water Environment Simulation School of EnvironmentBeijing Normal UniversityBeijing 100875China Research Center for Eco-Environmental Engineering Dongguan University of TechnologyDongguan 523808China

Hydrodechlorination is a promising technology for the remediation of water body contaminated with trichloroethylene(TCE).In this work,the liquid-phase hydrogenation of TCE by Raney Ni(R-Ni)and Pd/C under an open system have been studied,in which nascent H_(2)(Nas-H_(2))generated in situ from the cathode acted as a hydrogen *** results showed that TCE was completely eliminate from the solution through the synergistic effects of hydrodechlorination and air flotation due to the formation of continuous micro/nano-sized Nas-H_(2)bubbles from the ***,the effects of inorganic anions and organic solvents on R-Ni and Pd/C hydrogenation activity were investigated,*** results showed that NO_(3)^(-) and acetonitrile can form a competitive reaction with TCE;Sulfur with lone-pair electrons will cause irreversible poisoning to these two catalysts,and have a stronger inhibitory effect on Pd/*** work helps to realize the separation of volatile halogenated compounds from water environment and provides certain data support for the choice of catalyst in the actual liquid-phase hydrogenation system.

关键词： Nascent H_(2) Hydrogenation Air flotation Trichloroethylene Sulfur poisoning

Enhanced Power Allocation Scheme in Ultra-Dense Small Cell Network

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China Communications 2016年第2期13卷 21-29页

作者： GAO Yuehong CHENG Lei zhang Xin ZHU Yajun zhang yunfei Beijing University of Posts and Telecommunications BeijingChina Yulong Computer Telecommunication Scientific(Shenzhen)Co. LTDShenzhenChina

A feasible design of ultra-dense Small cell network involves an effective solution to the interference coordination especially in cell edge. In this paper, we propose a channel state and interference aware power allocation scheme(PAG) as an enhanced solution to improve the system performance, especially for the cell-edge users. Cournot model in Non-cooperative game is employed for power adjustment in Small cell clusters to increase cell-edge users' throughput by considering the power limitation and interference coordination. Additionally, we take iterative Water Filling scheme as a comparison to clarify that the PAG scheme has struck a favorable balance between system efficiency and fairness. Simulation results show that the proposed scheme contributes to the enhancement of edge users' throughput and cells' coverage. Moreover, the scheme is observed to show a stronger adaptability in denser Small cell networks.

关键词： Ultra-dense Small cell Interferencecoordination Non-cooperative game Utilityfunction

A 31-year Global Diurnal Sea Surface Temperature Dataset Created by an Ocean Mixed-Layer Model

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Advances in Atmospheric Sciences 2018年第12期35卷 1443-1454页

作者： Xiang LI Tiejun LING yunfei zhang Qian ZHOU Key Laboratory of Research on Marine Hazards Forecasting National Marine Environmental Forecasting CenterState Oceanic Administration

A dataset of hourly sea surface temperature(SST) from the period 1 January 1982 to 31 December 2012, and covering the global ocean at a resolution of 0.3°× 0.3°, was created using a validated ocean mixed-layer model(MLSST). The model inputs were heat flux and surface wind speed obtained from the Coupled Forecast System Reanalysis dataset. Comparisons with in-situ data from the Tropical Atmosphere Ocean array and the National Data Buoy Center showed that the MLSST fitted very well with observations, with a mean bias of 0.07℃, and a root-mean-square error(RMSE) and correlation coefficient of 0.37℃ and 0.98, respectively. Also, the MLSST fields successfully reproduced the diurnal cycle of SST in the in-situ data, with a mean bias of -0.005℃ and RMSE of 0.26℃. The 31-year climatology revealed that the diurnal range was small across most regions, with higher values in the eastern and western equatorial Pacific, northern Indian Ocean, western Central America, northwestern Australia, and several coastal regions. Significant seasonal variation of diurnal SST existed in all basins. In the Atlantic and Pacific basins, this seasonal pattern was oriented north–south, following the variation in solar insolation, whereas in the Indian basin it was dominated by monsoonal variability. At the interannual scale, the results highlighted the relationship between diurnal and interannual variations of SST, and revealed that the diurnal warming in the central equatorial Pacific could be a potential climatic indicator for ENSO prediction.

关键词： SST diurnal cycle mixed-layer model climatic variation

Effect of pH conditions on the depolymerization of Wucaiwan coal by mixed acids/ultrasound method and the product structures and performance

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International Journal of Coal Science & Technology 2017年第4期4卷 342-353页

作者： Bo zhang Halidan Maimaiti yunfei zhang Ming Wei Institute of Chemistry and Chemical Industry XinjiangUniversity Urumqi 830046 Xinjiang China State Key Laboratory of Fine Chemicals Dalian Universityof Technology Dalian 116024 China

The cleavage of the aliphatic chain or ether bond connecting the polycyclic aromatic hydrocarbons in coal can be achieved by not only hydrogenation reduction but also oxidative acid treatment. In this paper, coal samples from Wucaiwan in Xinjiang were pretreated with HNO3 followed by mixed acids/ultrasound treatment. The depolymerized coal samples obtained under different pH conditions were then separated by fractional washing. The structures and properties of the resulting coal samples were studied by elemental analysis, FT-IR, XRD, TG-DTA, TEM, UV-Vis, and PL. The results showed that when pH = 0.012, the obtained coal samples were fragments stripped off from the raw coal samples by ultrasound in strong acid conditions, aliphatic hydrocarbons linked with oxygen-containing groups such as nitro group, a small amount of small aromatic molecules and mineral salts; when pH -- 1.99-4.09, the obtained coal samples were polycyclic aromatic hydrocarbons linked with oxygen-containing groups such as nitro group,possessing the annulus wall of multilayer graphene fragment structures built up by sp2 carbons, and they are typical fluorescent substances of carbon nanoparticle structure. The former has no solubility in organic solvents, while the latter can be well dissolved in polar solvents such as acetone. All the depolymerized coal samples obtained under different pH conditions exhibited good absorption and ability of fluorescence emission.

关键词： Coal Depolymerization pH conditions Carbon dots Fluorescent

Recent improvements to the physical model of the Bohai Sea,the Yellow Sea and the East China Sea Operational Oceanography Forecasting System

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Acta Oceanologica Sinica 2021年第11期40卷 87-103页

作者： Ang Li Xueming Zhu yunfei zhang Shihe Ren Miaoyin zhang Ziqing Zu Hui Wang Key Laboratory of Marine Hazards Forecasting National Marine Environmental Forecasting CenterMinistry of Natural ResourcesBeijing 100081China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519000China

In order to satisfy the increasing demand for the marine forecasting capacity,the Bohai Sea,the Yellow Sea and the East China Sea Operational Oceanography Forecasting System(BYEOFS)has been upgraded and improved to Version *** on the Regional Ocean Modeling System(ROMS),a series of comparative experiments were conducted during the improvement process,including correcting topography,changing sea surface atmospheric forcing mode,adjusting open boundary conditions,and considering atmospheric pressure correction.(1)After the topography correction,the volume transport and meridional velocity maximum of Yellow Sea Warm Current increase obviously and the unreasonable bending of its axis around 36.1°N,123.5°E disappears.(2)After the change of sea surface forcing mode,an effective negative feedback mechanism is formed between predicted sea surface temperature(SST)by the ocean model and sea surface radiation fluxes *** simulation errors of SST decreased significantly,and the annual average of root-mean-square error(RMSE)decreased by about 18%.(3)The change of the eastern lateral boundary condition of baroclinic velocity from mixed Radiation-Nudging to Clamped makes the unreasonable westward current in Tsushima Strait disappear.(4)The adding of mean sea level pressure correction option which forms the mean sea level gradient from the Bohai Sea and the Yellow Sea to the western Pacific in winter and autumn is helpful to increasing the fluctuation of SLA and outflow of the Yellow Sea when the cold high air pressure system controls the Yellow Sea area.

关键词： Operational Oceanography Forecasting System East China Sea SST Yellow Sea Warm Current