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Reconstructing the flux-rope topology using the FOTE method

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Science China(Technological Sciences) 2019年第1期62卷 144-150页

作者： CHEN ZuZheng fu HuiShan WANG TieYan CAO Dong PENG FangZheng YANG Jian XU Yin School of Space and Environment Beihang UniversityBeijing 100083China

With high-resolution data of the Magnetospheric Multiscale(MMS) mission, we observe a magnetic flux rope(MFR) in the Earth's magnetosheath. This MFR, showing a clear bipolar variation of the magnetic field in the normal component to local current sheet, contains a strong core field. We use the FOTE method to reconstruct the topology of this MFR and find it is consistent with previous expectation. For the first time, the spiral field and core field of the MFR are both revealed from the FOTE method. Comparing topologies reconstructed at different times, we suggest that the axis of the MFR rotates about 88° at different spatial location. Shape and size of the normal projection to axis vary with the spatial location as well. Inside the MFR, a significant increase of plasma density from 40 to 80 cm^(-3), a sharp decrease of ion temperature from 200 to 50 eV, an enhancement of cold ions and a series of filamentary currents are found.

关键词： magnetic flux rope First-Order Taylor Expansion (FOTE)method reconstructing three-dimensional topology

Evolutionary processes and sources of high-nitrate haze episodes over Beijing,Spring

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Journal of Environmental Sciences 2017年第4期29卷 142-151页

作者： Ting Yang Yele Sun Wei Zhang Zifa Wang Xingang Liu Pingqing fu Xiquan Wang State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Aviation Meteorological Center of China Beijing 100021 China State Key Laboratory of Water Environment Simulation School of Environment Beijing Normal University Beijing 100089 China

Rare and consecutive high-nitrate haze pollution episodes were observed in Beijing in spring2012. We present detailed characterization of the sources and evolutionary mechanisms of this haze pollution, and focus on an episode that occurred between 15 and 26 April. Submicron aerosol species were found to be substantially elevated during haze episodes, and nitrates showed the largest increase and occupation（average： 32.2%） in non-refractory submicron particles（NR-PM1）, which did not occur in other seasons as previously reported. The haze episode（HE） was divided into three sub-episodes, HEa, HEb, and HEc. During HEa and HEc, a shallow boundary layer, stagnant meteorological conditions, and high humidity favored the formation of high-nitrate concentrations, which were mainly produced by three different processes —daytime photochemical production, gas-particle partitioning, and nighttime heterogeneous reactions — and the decline in visibility was mainly induced by ***, unlike HEa and HEc, during HEb, the contribution of high nitrates was partly from the transport of haze from the southeast of Beijing — the transport pathway was observed at ~800–1000 m by aerosol Lidar —and the decline in visibility during HEb was primarily caused by PM（2.5）. Our results provide useful information for air quality improvement strategies in Beijing during Spring.

关键词： Haze Nitrate Sources Lidar Aerosol Chemical Speciation Monitor Boundary layer

Numerical analysis of turbulent fluctuations around an axisymmetric body of revolution based on wall-modeled large eddy simulations

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Journal of Hydrodynamics 2023年第6期35卷 1041-1051页

作者： Kang-jian He fu-chang Zhou Wei-wen Zhao Jian-hua Wang De-cheng Wan Computational Marine Hydrodynamics Lab(CMHL) School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China Wuhan Second Ship Design and Research Institute Wuhan430205China

Wall-modeled large eddy simulation(WMLES)is used to investigate turbulent fluctuations around an axisymmetric body of *** study focuses on evaluating the ability of WMLES to predict the fluctuating flow over the axisymmetric hull and analyzing the evolution of turbulent fluctuations around the *** geometry is the DARPA SUBOFF bare model and the Reynolds number is 1.2×10^(7),based on the free-stream velocity and the length of the ***-wall flow structures and complex turbulent fluctuation fields are successfully ***-averaged flow quantities,such as time-averaged pressure and skin-friction coefficients,and time-averaged velocity profiles on the stern,achieved great agreements between WMLES results and experimental ***-similarity of time-averaged velocity defects within a self-similar coordinate up to twelve diameters from the tail.A comprehensive analysis of second-order statistics in the mid-body,stern,and wake regions is *** results agree well with experimental data and previous wall-resolved large eddy simulation(WRLES)results about root mean square(rms)of radial and axial fluctuating velocities at the *** fluctuations including turbulent kinetic energy(TKE)and second-order velocity statistics are identified as dual peak behavior and non-self-similar over the wake length,consistent with previous findings in the *** assessment enhances the understanding of WMLES capabilities in capturing complex fluctuating flow around axisymmetric geometries.

关键词： Turbulent fluctuations wall-modeled large eddy simulation(WMLES) turbulent boundary layer wake

Recent progress in high-entropy metallic glasses

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Journal of Materials Science & Technology 2023年第30期161卷 50-62页

作者： Hengwei Luan Keran Li Lingxiang Shi Wei Zhao Hengtong Bu Pan Gong Ke-fu Yao Wuzhen Laboratory Tongxiang 314500China School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China Department of Physics City University of Hong KongTat Chee AvenueKowloon999077Hong KongChina e City University of Hong Kong(Dongguan) Dongguan 523000China

High-entropy metallic glass(HEMG)is a new type of metallic material with high-entropy alloy-like com-position and amorphous structure,which render HEMGs unusual glass formation behaviors and unique *** recent years,fast research progress has been witnessed on the HEMGs,and thus a sys-tematic review is *** this review,we first introduce the concept of the HEMGs and summarize the developed ***,the glass-forming ability of the HEMGs is discussed,and the general rules are *** on the thermal stability of HEMGs,the effect of entropy on the energy states of HEMGs and the crystallization behavior of HEMGs are ***,the mechanical,magnetic,cat-alytic and other properties of HEMGs are presented,and the advantages and disadvantages of HEMGs are *** review can function as a quick guideline for overviewing the HEMG field.

关键词： High-entropy metallic glasses Glass-forming ability Thermal stability Mechanical property functional property

Synthesis of Highly Branched Poly(ε-caprolactone) by Self-condensing Atom Transfer Radical Polymerization of Macroinimers

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Chinese Chemical Letters 2006年第3期17卷 373-376页

作者： Rui Xue LIU Yan SHI Zhi Feng fu Shu Ke JIAO Key Laboratory of Science and Technology of Controllable Chemical Reactions Ministry of Education Beijing University of Chemical Technology Beijing 100029

Branched poly（ε-capmlactone） was synthesized by self-condensing atom transfer radical polymerization of macroinimer, α-acryloyoxy-ω-2-bromopropionyloxy poly（ε-caprolactone）, which was prepared by enzyme-catalyzed ring-opening polymerization of ε-caprolactone with 2-hydroxylethyl acrylate as initiator and esterification of the ω-hydroxyl group of the obtained poly（ε-caprolactone） by 2-bromopropionyl bromide.

关键词： Self-condensing vinyl polymerization atom transfer radical polymerization branched polymers poly(ε-caprolactone).

Tuning the local coordination environment of silver(Ⅰ) coordination networks with counterions for enhanced electrocatalytic CO_(2) reduction

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Science China Chemistry 2024年第5期67卷 1524-1530页

作者： Xiaofeng Cui Xueting Wang Cong fu Bing Liu Mei-Yan Gao Tingting Kong Yujie Xiong Anhui Engineering Research Center of Carbon Neutrality The Key Laboratory of Functional Molecular SolidsMinistry of EducationAnhui Laboratory of Molecular-Based MaterialsCollege of Chemistry and Materials ScienceAnhui Normal UniversityWuhu 241002China Department of Chemical Sciences Bernal InstituteUniversity of LimerickLimerick V94 T9PXRepublic of Ireland School of Chemistry and Materials Science University of Science and Technology of ChinaHefei 230026China School of Chemical and Material Engineering Jiangnan UniversityWuxi 214122China

Very recently, the local coordination environment of active sites has been found to strongly influence their performance in electrocatalytic CO_(2) reduction by tuning the intrinsic kinetics of CO_(2) activation and intermediate stabilization. It is imperative to elucidate the mechanism for such an influence towards the rational design of efficient catalysts;however, the complex interactions between the multiple factors involved in the system make it challenging to establish a clear structure–performance relationship. In this work, we chose ion-intercalated silver(I)-based coordination networks(AgCNs) with a well-defined structure as a model platform, which enables us to understand the regulation mechanism of counterions as the counterions are the only tuning factor involved in such a system. We prepared two isostructural Ag CNs with different intercalation ions or counterions of BF_(4)^(-) and ClO_(4)^(-)(named as AgCNs-BF_(4) and AgCNs-ClO_(4)) and found that the former has a more competitive CO_(2) electroreduction performance than the latter. AgCNs-BF_(4) achieves the highest Faradaic efficiency for CO_(2) to CO of 87.1% at-1.0 V(vs. RHE) with a higher partial current density, while AgCNs-ClO_(4) exhibits only 77.2% at the same applied *** characterizations and theoretical calculation reveal that the presence of BF_(4)^(-)is more favorable for stabilizing the COOH^(*) intermediate by weakening hydrogen bonds, which accounts for the superior activity of Ag CNs-BF_(4).

关键词： electrocatalytic CO_(2) reduction coordination networks local environment counterions intercalation ions

A modified θ projection model for constant load creep *** of the model

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Journal of Materials Science & Technology 2019年第1期35卷 223-230页

作者： Chao fu Yadong Chen Xiaofei Yuan Sammy Tin Stoichko Antonov Koichi Yagi Qiang Feng Beijing Advanced Innovation Center for Material Genome Engineering State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Department of Mechanical Materials & Aerospace Engineering Illinois Institute of Technology National Center for Materials Service Safety University of Science and Technology Beijing

Estimating long-term creep deformation and life of materials is an effective way to ensure the service safety and to reduce the cost of long-term integrity evaluation of high temperature structural *** the 1980 s, the θ projection model has been widely used for predicting creep lives due to its ability to capture the characteristic transitions observed in creep curves obtained under constant true stress conditions. However, the creep rupture behavior under constant load or engineering stress conditions cannot be simulated accurately using this model because of the different stress states. In this paper, creep curves obtained under constant load conditions were analyzed using a modified θ projection model by considering the increase in true stress with creep deformation during the creep tests. This model is expressed as ε = θ_1(1-e^(-θ_2t)) + θ3 e^(θ_4e^θ5^εt)-1, and was validated using the creep curves of K465 and DZ125 superalloys tested at a range of temperatures and engineering stresses. Moreover, it was shown that the predictive capability of the modified θ projection model was significantly improved over the original one, as it reduces the prediction uncertainty from a range of 10% to 20% to below 5%. Meanwhile,it was shown that the model can be reasonably used for predicting constant stress creep conditions, when appropriate parameters are used. The prediction performance of the modified model will be discussed in another paper. The results of this study show great potential for the evaluation and assessment of the service safety of structural materials used in applications where designs are limited by creep deformation.

关键词： Superalloy Creep Life prediction Modified θ projection model Constant load creep

Impacts of Drought and Human Activity on Vegetation Growth in the Grain for Green Program Region,China

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Chinese Geographical Science 2018年第3期28卷 470-481页

作者： WANG Hao LIU Guohua LI Zongshan YE Xin fu Bojie LV Yihe Department of Geography School of Geography and Tourism Shaanxi Normal University State Key Laboratory of Urban and Regional Ecology Research Center for Eco-Environmental Science Chinese Academy of Sciences Nanjing Institute of Environmental Sciences Ministry of Environmental Protection

The Chinese government adopted six ecological restoration programs to improve its natural environments. Although these programs have proven successful in improving local environments, some studies have questioned their performance when regions suffer from drought. Whether we should consider the effects of drought on vegetation change in assessments of the benefits of ecological restoration programs is unclear. Therefore, taking the Grain for Green Program(GGP) region as a study area, we estimated vegetation growth in the region from 2000–2010 to clarify the trends in vegetation and their driving forces. Results showed that: 1) vegetation growth increased in the GGP region during 2000–2010, with 59.4% of the area showing an increase in the Normalized Difference Vegetation Index(NDVI). This confirmed the benefits of the ecological restoration program. 2) Drought can affect the vegetation change trend, but human activity plays a significant role in altering vegetation growth, and the slight downward trend in the NDVI was not consistent with the severity of the drought. Positive human activity led to increased NDVI in 89.13% of areas. Of these, 22.52% suffered drought, but positive human activity offset the damage in part. 3) Results of this research suggest that appropriate human activity can maximize the benefits of ecological restoration programs and minimize the effects of extreme weather. We therefore recommend incorporating eco-risk assessment and scientific management mechanisms in the design and management of ecosystem restoration programs.

关键词： Grain for Green Program Normalized Difference Vegetation Index(NDVI) climate fluctuation human activity China

Enhanced conductivity and stability of Prussian blue cathodes in sodium-ion batteries by surface vapor-phase molecular selfassembly

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Nano Research 2024年第5期17卷 4221-4230页

作者： Tao Yuan Xiaopan fu Yuan Wang Mingjie Li Shuixin Xia Yuepeng Pang Shiyou Zheng School of Materials and Chemistry University of Shanghai for Science and TechnologyShanghai 200093China

With many merits such as facile synthesis,economy,and relatively high theoretical capacity,Prussian blue analogs(PBAs)are considered promising cathode materials for sodium-ion batteries(SIBs).However,their practical applications still suffer from a low actual specific capacity and inferior stability owing to the imperfect crystallinity,irreversible phase transition,and low intrinsic ***,a surface-modification technique for vapor-phase molecular self-assembly was developed to prepare Fe-based PBAs,specifically sodium iron hexacyanoferrate(NaFeHCF),with a uniform conductive polymer protective layer of polypyrrole(PPy)on the surface,resulting in NaFeHCF@*** incorporation of a PPy protective layer not only improves the electronic conductivity of NaFeHCF@PPy,but also effectively mitigates the dissolution of Fe-ions during ***,this advanced vapor-phase technique avoids Fe^(2+)oxidation and Na^(+)loss during liquid-phase surface *** NaFeHCF@PPy exhibited a remarkably enhanced cycling performance,with capacity retentions of 85.6%and 69.1%over 500 and 1000 cycles,respectively,at 200 mA/g,along with a superior rate performance up to 5 A/g(fast kinetics).Additionally,by adopting this strategy for Mn-based PBAs(NaMnHCF@PPy),we further demonstrated the universality of this method for PBA cathodes in SIBs.

关键词： sodium-ion battery cathode Prussian blue analogs surface modification vapor-phase molecular self-assembly