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Source emissions and climate change impacts on the multimedia transport and fate of persistent organic pollutants,Chaohu watershed,eastern China

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Journal of Environmental Sciences 2021年第11期33卷 15-25页

作者： Xianghui Cao Shouliang Huo Hanxiao Zhang Jiaqi Zheng Zhuoshi He Chunzi Ma Shuai Song State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental ScienceBeijing 100012China Beijing Normal University Beijing 100874China State Key Laboratory of Urban and Regional Ecology Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China

Emission intensity and climate change control the transport flux and fate of persistent organic pollutants(POPs)inmultiple environmental compartments.This study applied amultimedia model(BETR model)to explore alternations in the spatio-temporal trends of concentrations and transport flux of benzopyrene(BaP),phenanthrene(Phe),perfluorooctane sulfonates(PFOS)and polychlorinated biphenyls(PCBs)in the Chaohu watershed,located in the lower reaches of the Yangtze River,China in response to changes in source emissions and climate.The potential historic and future risks of these pollutants also were assessed.The results suggest that current trends in concentrations and transport were similar to that of their emissions between 2005 and 2018.During the next 100 years,temporal trends and spatial patterns were not predicted to change significantly,which is consistent with climate change.Based on sensitivity and correlation analyses,climate change had significant effects on multi-media concentrations and transport fluxes of BaP,Phe,PFOS and PCBs,and rainfall intensity was the predominant controlling factor.Risk quotients(RQs)of BaP and Phe-in soil increased from 0.42 to 0.95 and 0.06 to 0.35,respectively,from 2005 to 2090,indicating potential risks.The RQs of the other examined contaminants exhibited little potential risk in soil,water,or sediment.Based on spatial patterns,it was inferred that the ecosystem around Lake Chaohu is the most at risk.The study provides insights needed for local pollution control of POPs in the Chaohu watershed.In addition,the developed approach can be applied to other watersheds world-wide.

关键词： Climate change POP emissions Multimedia model Contaminant transport Risk assessment

Formation of the bow shock indentation: MHD simulation results

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Earth and Planetary Physics 2021年第3期5卷 259-269页

作者： BaoHang Qu JianYong Lu Ming Wang HuanZhi Yuan Yue Zhou Hanxiao Zhang Institute of Space Weather School of Math&StatisticsNanjing University of Information Science&TechnologyNanjing 210044China Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China

Simulation results from a global magnetohydrodynamic(MHD)model are used to examine whether the bow shock has an indentation and characterize its formation conditions,as well as its physical mechanism.The bow shock is identified by an increase in plasma density of the solar wind,and the indentation of the bow shock is determined by the shock flaring angle.It is shown that when the interplanetary magnetic field(IMF)is southward and the Alfvén Mach number(Mα)of solar wind is high(>5),the bow shock indentation can be clearly determined.The reason is that the outflow region of magnetic reconnection(MR)that occurs in the low latitude area under southward IMF blocks the original flow in the magnetosheath around the magnetopause,forming a high-speed zone and a low-speed zone that are upstream and downstream of each other.This structure hinders the surrounding flow in the magnetosheath,and the bow shock behind the structure widens and forms an indentation.When Mαis low,the magnetosheath is thicker and the disturbing effect of the MR outflow region is less obvious.Under northward IMF,MR occurs at high latitudes,and the outflow region formed by reconnection does not block the flow inside the magnetosheath,thus the indentation is harder to form.The study of the conditions and formation process of the bow shock indentation will help to improve the accuracy of bow shock models.

关键词： indentation of bow shock global MHD simulation interplanetary magnetic field Bz Alfvén Mach number

Image Super-Resolution Based on Generative Adversarial Networks: A Brief Review

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Computers, Materials & Continua 2020年第9期64卷 1977-1997页

作者： Kui Fu Jiansheng Peng Hanxiao Zhang Xiaoliang Wang Frank Jiang School of Physics and Mechanical and Electronic Engineering Hechi UniversityYizhou546300China School of Electrical and Information Engineering Guangxi University of Science and TechnologyLiuzhou545006China School of Computer Science and Engineering Hunan University of Science and TechnologyXiangtan411100China School of Information Technology Deakin UniversityGeelongVIC 3220Australia

Single image super resolution(SISR)is an important research content in the field of computer vision and image processing.With the rapid development of deep neural networks,different image super-resolution models have emerged.Compared to some traditional SISR methods,deep learning-based methods can complete the super-resolution tasks through a single image.In addition,compared with the SISR methods using traditional convolutional neural networks,SISR based on generative adversarial networks(GAN)has achieved the most advanced visual performance.In this review,we first explore the challenges faced by SISR and introduce some common datasets and evaluation metrics.Then,we review the improved network structures and loss functions of GAN-based perceptual SISR.Subsequently,the advantages and disadvantages of different networks are analyzed by multiple comparative experiments.Finally,we summarize the paper and look forward to the future development trends of GAN-based perceptual SISR.

关键词： Single image super-resolution generative adversarial networks deep learning computer vision

Apparent relationships between anthropogenic factors and climate change indicators and POPs deposition in a lacustrine system

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Journal of Environmental Sciences 2019年第9期31卷 174-182页

作者： Hanxiao Zhang Shouliang Huo Kevin M. Yeager Chaocan Li Beidou Xi Jingtian zhang Zhuoshi He Chunzi Ma State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental Science Beijing 100012 China Department Earth and Environmental Sciences University of Kentucky Lexington KY 40506 USA

Climate change and anthropogenic activities are expected to impact the environmental behaviors and fates of persistent organic pollutants(POPs), however, quantitative studies on these combined factors are scarce. In this study, dichlorodiphenyltrichloroethane(DDTs), polycyclic aromatic hydrocarbons(PAHs), and polychlorinated biphenyls(PCBs)were used as examples to identify how and when those factors may be related to the deposition of POPs in the sediment of Lake Chaohu, China, using generalized additive models(GAMs). Three historical trends of DDT, PAH, and PCB deposition were delineated in a dated sediment core encompassing ~100 years of historical record: a steady state or gradually increasing stage, a rapidly increasing stage, and a declining stage. The GAM results showed that aquatic total phosphorus(TP) concentrations and regional GDP(anthropogenic factors) were dominant contributors to POP accumulation rates in the lake sediment. The fitted relationships between air temperature and sedimentary DDT and PAH concentrations were linear and negative, while a positive linear relationship was found for PCBs, suggesting that Lake Chaohu may have become a net source for DDTs and PAHs, and a sink for PCBs, under a progressively warming climate.

关键词： POPs Lake sediment Generalized additive models Climate change

Magnetosphere response to the IMF turning from north to south

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Earth and Planetary Physics 2019年第1期3卷 8-16页

作者： JianYong Lu Hanxiao Zhang Ming Wang ChunLi Gu HaiYan Guan Institute of Space Weather School of Math & Statistics Nanjing University of Information Science & Technology Beijing Institute of Applied Meteorology School of Remote Sensing & Geomatics Engineering Nanjing University of Information Science & Technology

In this paper, the Space Weather Modeling Framework(SWMF) is used to simulate the real-time response of the magnetosphere to a solar wind event on June 5, 1998, in which the interplanetary magnetic field shifted its direction from north to south.Since most current models do not take into account convective effects of the inner magnetosphere, we first study the importance of Rice Convection Model(RCM) in the global model.We then focus on the following four aspects of the magnetosphere's response: the magnetosphere's density distribution, the structure of its magnetic field lines, the area of the polar cap boundary, and the corresponding ionospheric current change.We find that(1) when the IMF changes from north to south in this event, high magnetosheath density is observed to flow downstream along the magnetopause with the solar wind; low-latitude reconnection at dayside occurs under the southward IMF, while the magnetic field lines in the tail lobe caudal, caused by the nightside high latitude reconnection, extend into the interplanetary space.Open magnetic field lines exist simultaneously at both high and low latitudes at the magnetopause;(2) the area of the polar cap is obviously increased if the IMF turns from the north to the south; this observation is highly consistent with empirical observations;(3) the ionospheric field align current in the northern hemisphere is stronger than in the southern hemisphere and also increases as the IMF changes from north to south.SWMF with the Rice Convection effect provides reliable modeling of the magnetospheric and ionospheric response to this solar wind variation.

关键词： magnetosphere global MHD simulation polar cap magnetic reconnection

A Historical Sedimentary Record of Mercury in a Shallow Eutrophic Lake: Impacts of Human Activities and Climate Change

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Engineering 2019年第2期5卷 296-304页

作者： Hanxiao Zhang Shouliang Huo Kevin M. Yeager Beidou Xi Jingtian zhang Fengchang Wu State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental Science Beijing 100012 China Department of Earth and Environmental Sciences University of Kentucky Lexington KY 40506 USA

Mercury and its derivatives are hazardous environmental pollutants and could affect the aquatic ecosystems and human health by biomagnification. Lake sediments can provide important historical information regarding changes in pollution levels and thus trace anthropogenic or natural influences. This research investigates the 100-year history of mercury (Hg) deposition in sediments from Chao Lake, a shallow eutrophic lake in China. The results indicate that the Hg deposition history can be separated into three stages (pre-1960s, 1960s–1980s, and post-1980s) over the last 100 years. Before the 1960s, Hg concentrations in the sediment cores varied little and had no spatial difference. Since the 1960s, the concentration of Hg began to increase gradually, and showed a higher concentration of contamination in the western half of the lake region than in the eastern half of the lake region due to all kinds of centralized human-input sources. The influences of anthropogenic factors and hydrological change are revealed by analyzing correlations between Hg and heavy metals (Fe, Co, Cr, Cu, Mn, Pb, and Zn), stable carbon and nitrogen isotopes (d13C and d15N), nutrients, particle sizes, and meteorological factors. The results show that Hg pollution intensified after the 1960s, mainly due to hydrological change, rapid regional development and urbanization, and the proliferation of anthropogenic Hg sources. Furthermore, the temperature, wind speed, and evaporation are found to interactively influence the environmental behaviors and environmental fate of Hg.

关键词： Lake sediment Mercury Vertical distribution Anthropogenic activities

Size-Dependent Oxidation-Induced Phase Engineering for MOFs Derivatives Via Spatial Confinement Strategy Toward Enhanced Microwave Absorption

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Nano-Micro Letters 2022年第6期14卷 294-307页

作者： hanxiao Xu Guozheng zhang Yi Wang Mingqiang Ning Bo Ouyang Yang Zhao Ying Huang Panbo Liu School of Chemistry and Chemical Engineering μNorthwestern Polytechnical UniversityXi’an 710129People’s Republic of China Key Laboratory of Magnetic Materials and Devices Ningbo Institute of Materials Technology&EngineeringChinese Academy of SciencesNingbo 315201People’s Republic of China MIIT Key Laboratory of Semiconductor Microstructure and Quantum Sensing Nanjing University of Science and TechnologyNanjing 210094People’s Republic of China Department of Mechanical and Materials Engineering University of Western OntarioLondonON N6A 5B9Canada

Precisely reducing the size of metal-organic frameworks(MOFs)derivatives is an effective strategy to manipulate their phase engineering owing to size-dependent oxidation;however,the underlying relationship between the size of derivatives and phase engineering has not been clarified so far.Herein,a spatial confined growth strategy is proposed to encapsulate small-size MOFs derivatives into hollow carbon nanocages.It realizes that the hollow cavity shows a significant spatial confinement effect on the size of confined MOFs crystals and subsequently affects the dielectric polarization due to the phase hybridization with tunable coherent interfaces and heterojunctions owing to size-dependent oxidation motion,yielding to satisfied microwave attenuation with an optimal reflection loss of-50.6 d B and effective bandwidth of 6.6 GHz.Meanwhile,the effect of phase hybridization on dielectric polarization is deeply visualized,and the simulated calculation and electron holograms demonstrate that dielectric polarization is shown to be dominant dissipation mechanism in determining microwave absorption.This spatial confined growth strategy provides a versatile methodology for manipulating the size of MOFs derivatives and the understanding of size-dependent oxidation-induced phase hybridization offers a precise inspiration in optimizing dielectric polarization and microwave attenuation in theory.

关键词： Size-dependent oxidation Phase engineering Coherent interface Dielectric polarization Electron holography

Heteroatoms-doped carbon nanocages with enhanced dipolar and defective polarization toward light-weight microwave absorbers

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Nano Research 2022年第10期15卷 8705-8713页

作者： hanxiao Xu Guozheng zhang Yi Wang Yiruo Wang Huanlei Wang Ying Huang Panbo Liu School of Chemistry and Chemical Engineering Northwestern Polytechnical UniversityXi’an 710129China School of Materials Science and Engineering Ocean University of ChinaQingdao 266100China

Light-weight and exceptional microwave absorption are two vital characteristics for microwave absorbers in practical applications,but still face challenges.Herein,we employ a sacrificial template strategy to fabricate heteroatoms-doped carbon nanocages(CNs)via chemical vapor deposition,in which heteroatoms are simultaneously doped into the carbon frameworks by bubbling flowing source liquid.Compared with CNs,doped heteroatoms,accompanied with the inevitably defective arrangements in the lattice,not only decrease the electrical conductivity and balance the impedance characteristics,but also introduce structuralchemical defects and trigger dominant dipolar/defect polarization.As a result,both the minimum reflection loss(R_(L,min))and effective absorption bandwidth(EAB)greatly increase at an ultralow filler loading of 5 wt.%owing to internal hollow void and high specific surface area.The R_(L,min) values reach−53.6,−43.2,and−50.1 dB for N-CNs,S-CNs,and N,S-CNs with the corresponding EAB of 4.9,2.5,and 3.1 GHz,respectively.Furthermore,this work provides an effective strategy for the construction of heteroatoms-doped hollow carbon frameworks in large-scale production and the obtained doped carbon nanocages can be used as light-weight and high-performance microwave absorbers.

关键词： carbon nanocages hollow structure heteroatoms dipolar resonance microwave absorption

Single-photon-level light storage with distributed Rydberg excitations in cold atoms

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Frontiers of physics 2022年第2期17卷 25-32页

作者： Hanxiao Zhang Jinhui Wu M.Artoni G.C.La Rocca Center for Quantum Sciences and School of Physics Northeast Normal UniversityChangchun 130024China Department of Engineering and Information Technology and Istituto Nazionale di Ottica(INO-CNR) Brescia University25133 BresciaItaly Scuola Normale Superiore and CNISM 56126 PisaItaly

We present an improved version of the superatom(SA)model to examine the slow-light dynamics of a few-photons signal field in cold Rydberg atoms with van der Waals(vdW)interactions.A main feature of this version is that it promises consistent estimations on total Rydberg excitations based on dynamic equations of SAs or atoms.We consider two specific cases in which the incident signal field contains more photons with a smaller detuning or less photons with a larger detuning so as to realize the single-photon-level light storage.It is found that vdW interactions play a significant role even for the slow-light dynamics of a single-photon signal field as distributed Rydberg excitations are inevitable in the picture of dark-state polariton.Moreover,the stored(retrieved)signal field exhibits a clearly asymmetric(more symmetric)profile because its leading and trailing edges undergo different(identical)traveling journeys,and higher storage/retrieval efficiencies with well preserved profiles apply only to weaker and well detuned signal fields.These findings are crucial to understand the nontrivial interplay of single-photon-level light storage and distributed Rydberg excitations.

关键词： few-photons light storage distributed Rydberg excitation cold Rydberg atom improved superatom model