The effect of antibacterial adhesive on the biological corrosion resistance of mortar in seawater environment was studied by means of scanning electron microscope,thermogravimetric analysis,X-ray diffraction,Fourier t...The effect of antibacterial adhesive on the biological corrosion resistance of mortar in seawater environment was studied by means of scanning electron microscope,thermogravimetric analysis,X-ray diffraction,Fourier transform infrared spectroscopy,and ultra-depth microscope.The results show that the antibacterial adhesive can effectively inhibit the growth of sulfur-oxidizing bacteria in seawater,hinder their metabolism to produce biological sulfate,and reduce the formation of destructive product gypsum.The mineral composition and thermal analysis showed that the peak value of plaster diffraction peak and the mass loss of plaster dehydration in antibacterial adhesive group were significantly lower than those in blank group(without protective coating group).In addition,the electric flux of chloride ions(>400 C)in the blank group of mortar samples was higher than that in the antibacterial adhesive group(<200 C),indicating that the antibacterial adhesive can effectively reduce the permeability of chloride ions in mortar,and thus hinder the Cl-erosion in seawater.展开更多
Cirrus clouds play a crucial role in the energy balance of the Earth-atmosphere system.We investigated the spatiotemporal variations of cirrus over the South China Sea(SCS)using satellite data(MOD08,MYD08,CALIPSO)and ...Cirrus clouds play a crucial role in the energy balance of the Earth-atmosphere system.We investigated the spatiotemporal variations of cirrus over the South China Sea(SCS)using satellite data(MOD08,MYD08,CALIPSO)and reanalysis data(MERRA-2)from March 2007 to February 2015(eight years).The horizontal distribution reveals lower cirrus fraction values in the northern SCS and higher values in the southern region,with minima observed in March and April and maxima sequentially occurring in August(northern SCS,NSCS),September(middle SCS,MSCS),and December(southern SCS,SSCS).Vertically,the cirrus fraction peaks in summer and reaches its lowest levels in spring.Opaque cirrus dominates during summer in the NSCS and MSCS,comprising 53.6%and 55.9%,respectively,while the SSCS exhibits a higher frequency of opaque cirrus relative to other cloud types.Subvisible cirrus clouds have the lowest frequency year-round,whereas thin cirrus is most prominent in winter in the NSCS(46.3%)and in spring in the MSCS(45.3%).A case study from September 2021 further explores the influence of ice crystal habits on brightness temperature(BT)over the SCS.Simulations utilizing five ice crystal shapes from the ARTS DDA(Atmospheric Radiative Transfer Simulator Discrete Dipole Approximation)database and the RTTOV 12.4 radiative transfer model reveal that the 8-column-aggregate shape best represents BT in the NSCS and SSCS,while the large-block-aggregate shape performs better in the SSCS.展开更多
Low-velocity impact tests are carried out to explore the energy absorption characteristics of bio-inspired lattices,mimicking the architecture of the marine sponge organism Euplectella aspergillum.These sea sponge-ins...Low-velocity impact tests are carried out to explore the energy absorption characteristics of bio-inspired lattices,mimicking the architecture of the marine sponge organism Euplectella aspergillum.These sea sponge-inspired lattice structures feature a square-grid 2D lattice with double diagonal bracings and are additively manufactured via digital light processing(DLP).The collapse strength and energy absorption capacity of sea sponge lattice structures are evaluated under various impact conditions and are compared to those of their constituent square-grid and double diagonal lattices.This study demonstrates that sea sponge lattices can achieve an 11-fold increase in energy absorption compared to the square-grid lattice,due to the stabilizing effect of the double diagonal bracings prompting the structure to collapse layer-bylayer under impact.By adjusting the thickness ratio in the sea sponge lattice,up to 76.7%increment in energy absorption is attained.It is also shown that sea-sponge lattices outperform well-established energy-absorbing materials of equal weight,such as hexagonal honeycombs,confirming their significant potential for impact mitigation.Additionally,this research highlights the enhancements in energy absorption achieved by adding a small amount(0.015 phr)of Multi-Walled Carbon Nanotubes(MWCNTs)to the photocurable resin,thus unlocking new possibilities for the design of innovative lightweight structures with multifunctional attributes.展开更多
While reinforcement learning-based underwater acoustic adaptive modulation shows promise for enabling environment-adaptive communication as supported by extensive simulation-based research,its practical performance re...While reinforcement learning-based underwater acoustic adaptive modulation shows promise for enabling environment-adaptive communication as supported by extensive simulation-based research,its practical performance remains underexplored in field investigations.To evaluate the practical applicability of this emerging technique in adverse shallow sea channels,a field experiment was conducted using three communication modes:orthogonal frequency division multiplexing(OFDM),M-ary frequency-shift keying(MFSK),and direct sequence spread spectrum(DSSS)for reinforcement learning-driven adaptive modulation.Specifically,a Q-learning method is used to select the optimal modulation mode according to the channel quality quantified by signal-to-noise ratio,multipath spread length,and Doppler frequency offset.Experimental results demonstrate that the reinforcement learning-based adaptive modulation scheme outperformed fixed threshold detection in terms of total throughput and average bit error rate,surpassing conventional adaptive modulation strategies.展开更多
针对某柴油皮卡发动机噪声大、隔声性能不足问题,提出一种基于统计能量分析(statistical energy analysis,SEA)与发动机噪声衰减结合的噪声优化方法。首先,建立了一种基于不同厚度材料插入损失与表面吸声系数的整车SEA模型;其次,提出了...针对某柴油皮卡发动机噪声大、隔声性能不足问题,提出一种基于统计能量分析(statistical energy analysis,SEA)与发动机噪声衰减结合的噪声优化方法。首先,建立了一种基于不同厚度材料插入损失与表面吸声系数的整车SEA模型;其次,提出了一种发动机噪声衰减的评估方法,通过实测与SEA仿真进行对标,保证了SEA模型的精确性;然后,基于SEA模型进行能量贡献度占比分析,识别了发动机噪声传递的关键路径;最后,通过优化前围隔音垫、翼子板隔断、中通道隔音垫及侧窗玻璃等关键零件,发动机噪声衰减量提升2 dB~5 dB,道路加速工况车内500 Hz以上噪声优化1 dB~5 dB,语言清晰度提升4%~12%AI。展开更多
Drought across Northwest China in late spring has exerted a vital effect on the local climate and agricultural production,and has been alleviated during the past decades.This study explored the influence of the preced...Drought across Northwest China in late spring has exerted a vital effect on the local climate and agricultural production,and has been alleviated during the past decades.This study explored the influence of the preceding Arctic sea ice on the May drought in Northwest China caused by the precipitation deficit.Further analysis indicated that when the Greenland Sea ice concentration is abnormally high during February to April,the dry conditions in Northwest China tend to be alleviated.The increase of sea ice in the Greenland Sea can excite a meridional circulation,which causes sea surface temperature(SST)anomalies in the North Atlantic via the sea-air interaction,manifested as significant warm SST anomalies over the south of Greenland and the subtropical North Atlantic,but negative SST anomalies over the west of the Azores.This abnormal SST pattern maintains to May and triggers a zonal wave train from the North Atlantic through Scandinavia and Central Asia to Northwest China,leading to abnormal cyclones in Northwest China.Consequently,Northwest China experiences a more humid climate than usual.展开更多
Deep sea,with rich oil,gas,and mineral resources,plays an increasingly crucial role in scientific and industrial realms.However,the highly corrosive feature of deep sea hinders further exploration and development,whic...Deep sea,with rich oil,gas,and mineral resources,plays an increasingly crucial role in scientific and industrial realms.However,the highly corrosive feature of deep sea hinders further exploration and development,which requires metal materials with robust corrosion resistance.This review covers an in-depth and all-around overview of the up-to-date advances in corrosion and protection of metals in deep-sea environment.Firstly,the unique characteristics of deep-sea environment are summarized in detail.Subsequently,the corrosion performances of metals in both in situ and simulated deep-sea environments are illustrated systematically.Furthermore,corrosion prevent strategies of metals,including sacrificial anode protection,organic coatings,as well as coatings achieved by physical vapor deposition(PVD coatings),are highlighted.Finally,we outline current challenges and development trends of corrosion and protection of metals in deep-sea environment in the future.The purpose of this review is not only to summarize the recent progress on metal corrosion and protection in deep sea,but also to aid us in understanding them more comprehensively and deeply in a short time,so as to boost their fast development.展开更多
This study investigates the influence of major climatic modes on the interannual variability of the annual minimum extent of Antarctic sea ice.It shows that the Southern Annular Mode(SAM),the Indian Ocean Dipole(IOD),...This study investigates the influence of major climatic modes on the interannual variability of the annual minimum extent of Antarctic sea ice.It shows that the Southern Annular Mode(SAM),the Indian Ocean Dipole(IOD),and the El Niño-Southern Oscillation(ENSO),along with the total sea ice condition during the preceding spring,serve as precursor signals of February sea ice extent(SIE).These climate modes interact,energizing the Pacific-South American pattern(PSA),which deepens and shifts the Amundsen Sea Low(ASL)westward in spring.This pattern generates a dipole sea ice anomaly characterized by an increase in sea ice in the northern Ross Sea but a decrease in ice in the Bellingshausen and northern Weddell Seas.However,as the season transitions into summer,the ASL exerts a pronounced delayed effect,contributing to widespread sea ice loss across West Antarctica.Strong southerly winds on the western flank of the ASL push sea ice away from the inner Ross Sea,exposing coastal waters that absorb solar radiation,thereby accelerating ice melt through positive ice-albedo feedback.Simultaneously,northwesterly winds on the eastern flank transport warm air toward the Bellingshausen and northern Weddell Seas,intensifying ice loss in these regions.Furthermore,the active PSA is accompanied by a tripole sea surface temperature pattern characterized by warming in the Weddell Sea,which promotes continued ice melt.The co-occurrence of an exceptionally positive SAM,a La Niña,and a strong negative IOD during spring 2022,combined with lower-than-normal total spring SIE,ultimately contributed to the record-low Antarctic SIE observed in February 2023.展开更多
The ocean serves as a repository for various types of artificial nanoparticles.Nanoplastics(NPs)and nano zinc oxide(nZnO),which are frequently employed in personal care products and food packaging materials,are likely...The ocean serves as a repository for various types of artificial nanoparticles.Nanoplastics(NPs)and nano zinc oxide(nZnO),which are frequently employed in personal care products and food packaging materials,are likely simultaneously released and eventually into the ocean with surface runoff.Therefore,their mutual influence and shared destiny in marine environment cannot be ignored.This study examined how nanomaterials interacted and transported through sea sand in various salinity conditions.Results showed that NPs remained dispersed in brine,while nZnO formed homoaggregates.In seawater of 35 practical salinity units(PSU),nZnO formed heteroaggregates with NPs,inhibiting NPs mobility and decreasing the recovered mass percentage(Meff)from 24.52%to 12.65%.In 3.5 PSU brackish water,nZnO did not significantly aggregate with NPs,and thus barely affected their mobility.However,NPs greatly enhanced nZnO transport with Meff increasing from 14.20%to 25.08%,attributed to the carrier effect of higher mobility NPs.Cotransport from brackishwater to seawater was simulated in salinity change experiments and revealed a critical salinity threshold of 10.4 PSU,below which the mobility of NPs was not affected by coexisting nZnO and above which nZnO strongly inhibited NP transport.This study highlights the importance of considering the mutual influence and shared destiny of artificial nanoparticles in the marine environment and how their interaction and cotransport are dependent on changes in seawater salinity.展开更多
As one of the strongest convection bands in the Southern Hemisphere,the South Pacific Convergence Zone(SPCZ)substantially influences the variabilities in the atmospheric circulation and Antarctic climate.In this study...As one of the strongest convection bands in the Southern Hemisphere,the South Pacific Convergence Zone(SPCZ)substantially influences the variabilities in the atmospheric circulation and Antarctic climate.In this study,it is revealed that the intensity of the SPCZ can change the characteristics of sea ice in the West Antarctica during austral autumn,which is significantly independent of the El Niño-Southern Oscillation(ENSO).Observational and numerical results suggest that a stronger-than-usual SPCZ can generate a poleward-propagating Rossby wave train along a great circular route and induce a weakening of the Amundsen Sea Low(ASL)near West Antarctica,which may somewhat offset the teleconnections exerted by ENSO.These changes in the strength and zonal extent of ASL is noticeable and robustly lead to a tripole response of sea-ice perturbations in the Ross,Amundsen,and Weddell Seas.We find that the wind-driven dynamical processes determine the local sea-ice changes,while the influence from thermodynamic processes is trivial.This research underscores the need to consider the SPCZ variability for a comprehensive understanding of sea-ice changes in West Antarctica on interannual timescales.展开更多
As a crucial component of the Earth’s climate system,Antarctic sea ice has demonstrated significant variability over the satellite era.Here,we identify a remarkable decadal transition in the total Antarctic Sea Ice E...As a crucial component of the Earth’s climate system,Antarctic sea ice has demonstrated significant variability over the satellite era.Here,we identify a remarkable decadal transition in the total Antarctic Sea Ice Extent(SIE).The stage from 1979 to 2006 is characterized by high-frequency(i.e.,seasonal to interannual)temporal variability in SIE and zonal asymmetry in Sea Ice Concentration(SIC),which is primarily under the control of the Amundsen Sea Low(ASL).After 2007,however,sea ice changes exhibit a more spatially homogeneous pattern in SIC and a more temporally long-lasting mode in SIE.Further analysis reveals that sea ice-ocean interaction plays a major role in the low-frequency(i.e.,multiannual)variability of Antarctic sea ice from 2007−22.The related physical process is inferred to manifest as a strong coupling between the surface and the subsurface ocean layers,involving enhanced vertical convection and the downward delivery of the surface anomalies related to ice melting and freezing processes,thus maintaining the SIE anomalies for a longer time.Furthermore,this process mainly occurs in the Amundsen-Bellingshausen Sea(ABS)sector,and the weakened subsurface ocean stratification is the key factor triggering the coupling process in this region.We find that the Circumpolar Deep Water(CDW)over the ABS sector continued to shoal before 2007 and remained stable thereafter.It is speculated that the shoaling of the CDW may be a possible driver leading to the weakening of the subsurface stratification.展开更多
Hyperlipidemia constitutes a critical factor in the pathogenesis of vascular disease and gut microbiota dysbiosis.This study aims to investigate the role of sea buckthorn fruit oil(SBFO)in ameliorating hyperlipidemia,...Hyperlipidemia constitutes a critical factor in the pathogenesis of vascular disease and gut microbiota dysbiosis.This study aims to investigate the role of sea buckthorn fruit oil(SBFO)in ameliorating hyperlipidemia,modulating gut microbiota,and elucidating the underlying mechanisms of its lipid-lowering effects.SBFO intervention in hyperlipidemic mice significantly reduced body weight and visceral adiposity index while mitigating symptoms associated with hyperlipidemia,including dyslipidemia,infla mmation,liver damage,and endothelial dysfunction.Real-time quantitative PCR and Western blot analyses revealed that SBFO enhanced the response of free fatty acid oxidation and breakdown(adenosine 5'-monophosphateactivated protein kinaseα,carnitine palmitoyltransferase1a,peroxisome proliferator-activated receptorα,and peroxisome proliferator-activated receptorγ)while suppressing the synthesis of triglycerides and fatty acids(sterol-regulatory element binding protein 1,fatty acid synthase,and acetyl CoA carboxylase)at the gene and protein expression levels.Moreover,SBFO intervention enriched the gut microbiota of hyperlipidemic mice by increasing the relative abundances of Lactobacillus,Faecalibaculum,and Allobaculum,while decreasing the Firmicutes/Bacteroidetes ratio.These findings suggest that SBFO exhibits promising therapeutic potential in attenuating hyperlipidemia in mice through the regulation of lipid metabolism and modulation of gut microbiota.展开更多
Southerly moisture surges over the central South China Sea(SCS)are characterized by the strengthening of lowlevel southerlies that transport moisture northward from the Pacific or Indian Oceans to South China.These su...Southerly moisture surges over the central South China Sea(SCS)are characterized by the strengthening of lowlevel southerlies that transport moisture northward from the Pacific or Indian Oceans to South China.These surge events typically occur for days in the early-summer season(from April to June)and can lead to heavy rains in South China.This study categorizes surge events into three types of flow patterns and examines their multiscale variations and impacts on rainfall.The first type occurs mainly in April,with the southeasterlies enhanced by a deepening trough in South China and the western Pacific subtropical high established over the SCS.The second type of surge events mostly appears in June,featuring the prevailing southwesterlies of summer monsoon from the Indian Ocean during the active phases of intraseasonal oscillations.Most surge events exhibit semi-diurnal variations with morning and afternoon peaks of northward moisture fluxes.Specifically,the first type features a dominant afternoon peak,while the second type shows a dominant early-morning peak,which is induced by thermal contrast between the Indochina Peninsula and the SCS.In general,the surge events enhance moisture convergence and increase rainfall downstream in South China,but they show some regional differences.The second type strengthens moisture convergence and rainfall in coastal regions with a morning peak.In contrast,the first type enhances inland rainfall with a morning peak,while moisture divergence dominates coastal regions.The third type of surge events denotes transitional conditions between the first two types,in terms of atmospheric circulations,diurnal cycles,and rainfall patterns.These results highlight a diversity of regional moisture surges and related rainfall ranging from diurnal to sub-seasonal scales.展开更多
The Fushan Depression is one of the petroliferous depressions in the Beibuwan Basin,South China Sea.Previous studies have preliminarily explored the origin and source of crude oils in some areas of this depression.Nev...The Fushan Depression is one of the petroliferous depressions in the Beibuwan Basin,South China Sea.Previous studies have preliminarily explored the origin and source of crude oils in some areas of this depression.Nevertheless,no systematic investigations on the classification and origin of oils and hy-drocarbon migration processes have been made for the entire petroleum system in this depression,which has significantly hindered the hydrocarbon exploration in the region.A total of 32 mudstone and 58 oil samples from the Fushan Depression were analyzed to definite the detailed oil-source correlation within the sequence and sedimentary framework.The organic matter of third member of Paleogene Liushagang Formation(Els(3))source rocks,both deltaic and lacustrine mudstone,are algal-dominated with high abundance of C_(23)tricyclic terpane and C_(30)4-methylsteranes.The deltaic source rocks occur-ring in the first member(Els_(1))and second member(Els_(2))of the Paleogene Liushagang Formation are characterized by high abundance of C_(19+20)tricyclic terpane and oleanane,reflecting a more terrestrial plants contribution.While lacustrine source rocks of Els_(1)and Els_(2)display the reduced input of terrige-nous organic matter with relatively low abundance of C 19+20 tricyclic terpane and oleanane.Three types of oils were identified by their biomarker compositions in this study.Most of the oils discovered in the Huachang and Bailian Els_(1)reservoir belong to group A and were derived from lacustrine source rocks of Els_(1)and Els_(2).Group B oils are found within the Els_(1)and Els_(2)reservoirs,showing a close relation to the deltaic source rocks of Els_(1)and Els_(2),respectively.Group C oils,occurring in the Els3 reservoirs,have a good affinity with the Els3 source rocks.The spatial distribution and accumulation of different groups of oils are mainly controlled by the sedimentary facies and specific structural conditions.The Els_(2)reservoir in the Yong'an area belonging to Group B oil,are adjacent to the source kitchen and could be considered as the favorable exploration area in the future.展开更多
Synthetic aperture radar(SAR)aboard SEASAT was first launched in 1978.At the beginning of the 21st century,the Chinese remote sensing community recognized the urgent need to develop domestic SAR capabilities.Unlike sc...Synthetic aperture radar(SAR)aboard SEASAT was first launched in 1978.At the beginning of the 21st century,the Chinese remote sensing community recognized the urgent need to develop domestic SAR capabilities.Unlike scatterometers and al-timeters,space-borne SAR offers high-resolution images of the ocean,regardless of weather conditions or time of day.SAR imagery provides rich information about the sea surface,capturing complicated dynamic processes in the upper layers of the ocean,particular-ly in relation to tropical cyclones.Over the past four decades,the advantages of SAR have been increasingly recognized,leading to notable marine applications,especially in the development of algorithms for retrieving wind and wave data from SAR images.This study reviews the history,progress,and future outlook of SAR-based monitoring of sea surface wind and waves.In particular,the ap-plicability of various SAR wind and wave algorithms is systematically investigated,with a particular focus on their performance un-der extreme sea conditions.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.52278269,52278268,52178264)Tianjin Outstanding Young Scholars Science Fund Project(No.22JCJQJC00020)Key Project of Tianjin Natural Science Foundation(No.23JCZDJC00430)。
文摘The effect of antibacterial adhesive on the biological corrosion resistance of mortar in seawater environment was studied by means of scanning electron microscope,thermogravimetric analysis,X-ray diffraction,Fourier transform infrared spectroscopy,and ultra-depth microscope.The results show that the antibacterial adhesive can effectively inhibit the growth of sulfur-oxidizing bacteria in seawater,hinder their metabolism to produce biological sulfate,and reduce the formation of destructive product gypsum.The mineral composition and thermal analysis showed that the peak value of plaster diffraction peak and the mass loss of plaster dehydration in antibacterial adhesive group were significantly lower than those in blank group(without protective coating group).In addition,the electric flux of chloride ions(>400 C)in the blank group of mortar samples was higher than that in the antibacterial adhesive group(<200 C),indicating that the antibacterial adhesive can effectively reduce the permeability of chloride ions in mortar,and thus hinder the Cl-erosion in seawater.
基金supported by the National Natural Science Foundation of China(Grant Nos.42027804,41775026,and 41075012)。
文摘Cirrus clouds play a crucial role in the energy balance of the Earth-atmosphere system.We investigated the spatiotemporal variations of cirrus over the South China Sea(SCS)using satellite data(MOD08,MYD08,CALIPSO)and reanalysis data(MERRA-2)from March 2007 to February 2015(eight years).The horizontal distribution reveals lower cirrus fraction values in the northern SCS and higher values in the southern region,with minima observed in March and April and maxima sequentially occurring in August(northern SCS,NSCS),September(middle SCS,MSCS),and December(southern SCS,SSCS).Vertically,the cirrus fraction peaks in summer and reaches its lowest levels in spring.Opaque cirrus dominates during summer in the NSCS and MSCS,comprising 53.6%and 55.9%,respectively,while the SSCS exhibits a higher frequency of opaque cirrus relative to other cloud types.Subvisible cirrus clouds have the lowest frequency year-round,whereas thin cirrus is most prominent in winter in the NSCS(46.3%)and in spring in the MSCS(45.3%).A case study from September 2021 further explores the influence of ice crystal habits on brightness temperature(BT)over the SCS.Simulations utilizing five ice crystal shapes from the ARTS DDA(Atmospheric Radiative Transfer Simulator Discrete Dipole Approximation)database and the RTTOV 12.4 radiative transfer model reveal that the 8-column-aggregate shape best represents BT in the NSCS and SSCS,while the large-block-aggregate shape performs better in the SSCS.
基金supported by the Khalifa University of Science and Technology internal grants(Nos.2021-CIRA-109,2020-CIRA-007,and 2020-CIRA-024).
文摘Low-velocity impact tests are carried out to explore the energy absorption characteristics of bio-inspired lattices,mimicking the architecture of the marine sponge organism Euplectella aspergillum.These sea sponge-inspired lattice structures feature a square-grid 2D lattice with double diagonal bracings and are additively manufactured via digital light processing(DLP).The collapse strength and energy absorption capacity of sea sponge lattice structures are evaluated under various impact conditions and are compared to those of their constituent square-grid and double diagonal lattices.This study demonstrates that sea sponge lattices can achieve an 11-fold increase in energy absorption compared to the square-grid lattice,due to the stabilizing effect of the double diagonal bracings prompting the structure to collapse layer-bylayer under impact.By adjusting the thickness ratio in the sea sponge lattice,up to 76.7%increment in energy absorption is attained.It is also shown that sea-sponge lattices outperform well-established energy-absorbing materials of equal weight,such as hexagonal honeycombs,confirming their significant potential for impact mitigation.Additionally,this research highlights the enhancements in energy absorption achieved by adding a small amount(0.015 phr)of Multi-Walled Carbon Nanotubes(MWCNTs)to the photocurable resin,thus unlocking new possibilities for the design of innovative lightweight structures with multifunctional attributes.
基金funding from the National Key Research and Development Program of China(No.2018YFE0110000)the National Natural Science Foundation of China(No.11274259,No.11574258)the Science and Technology Commission Foundation of Shanghai(21DZ1205500)in support of the present research.
文摘While reinforcement learning-based underwater acoustic adaptive modulation shows promise for enabling environment-adaptive communication as supported by extensive simulation-based research,its practical performance remains underexplored in field investigations.To evaluate the practical applicability of this emerging technique in adverse shallow sea channels,a field experiment was conducted using three communication modes:orthogonal frequency division multiplexing(OFDM),M-ary frequency-shift keying(MFSK),and direct sequence spread spectrum(DSSS)for reinforcement learning-driven adaptive modulation.Specifically,a Q-learning method is used to select the optimal modulation mode according to the channel quality quantified by signal-to-noise ratio,multipath spread length,and Doppler frequency offset.Experimental results demonstrate that the reinforcement learning-based adaptive modulation scheme outperformed fixed threshold detection in terms of total throughput and average bit error rate,surpassing conventional adaptive modulation strategies.
基金supported by the National Natural Science Foun-dation of China [grant numbers 41991281 and 42005028]。
文摘Drought across Northwest China in late spring has exerted a vital effect on the local climate and agricultural production,and has been alleviated during the past decades.This study explored the influence of the preceding Arctic sea ice on the May drought in Northwest China caused by the precipitation deficit.Further analysis indicated that when the Greenland Sea ice concentration is abnormally high during February to April,the dry conditions in Northwest China tend to be alleviated.The increase of sea ice in the Greenland Sea can excite a meridional circulation,which causes sea surface temperature(SST)anomalies in the North Atlantic via the sea-air interaction,manifested as significant warm SST anomalies over the south of Greenland and the subtropical North Atlantic,but negative SST anomalies over the west of the Azores.This abnormal SST pattern maintains to May and triggers a zonal wave train from the North Atlantic through Scandinavia and Central Asia to Northwest China,leading to abnormal cyclones in Northwest China.Consequently,Northwest China experiences a more humid climate than usual.
基金the National Key R&D Program of China(No.2022YFB3808800)the National Natural Science Foundation of China(Nos.52301406 and 52375219)+2 种基金the Natural Science Foundation of Zhejiang Province(No.LR21E050001)the China Postdoctoral Science Foundation(No.2023M733600)the Ningbo Natural Science Foundation(No.2023J329).
文摘Deep sea,with rich oil,gas,and mineral resources,plays an increasingly crucial role in scientific and industrial realms.However,the highly corrosive feature of deep sea hinders further exploration and development,which requires metal materials with robust corrosion resistance.This review covers an in-depth and all-around overview of the up-to-date advances in corrosion and protection of metals in deep-sea environment.Firstly,the unique characteristics of deep-sea environment are summarized in detail.Subsequently,the corrosion performances of metals in both in situ and simulated deep-sea environments are illustrated systematically.Furthermore,corrosion prevent strategies of metals,including sacrificial anode protection,organic coatings,as well as coatings achieved by physical vapor deposition(PVD coatings),are highlighted.Finally,we outline current challenges and development trends of corrosion and protection of metals in deep-sea environment in the future.The purpose of this review is not only to summarize the recent progress on metal corrosion and protection in deep sea,but also to aid us in understanding them more comprehensively and deeply in a short time,so as to boost their fast development.
基金supported by the National Natural Science Foundation of China (Grant Nos.42288101 and 42375045)
文摘This study investigates the influence of major climatic modes on the interannual variability of the annual minimum extent of Antarctic sea ice.It shows that the Southern Annular Mode(SAM),the Indian Ocean Dipole(IOD),and the El Niño-Southern Oscillation(ENSO),along with the total sea ice condition during the preceding spring,serve as precursor signals of February sea ice extent(SIE).These climate modes interact,energizing the Pacific-South American pattern(PSA),which deepens and shifts the Amundsen Sea Low(ASL)westward in spring.This pattern generates a dipole sea ice anomaly characterized by an increase in sea ice in the northern Ross Sea but a decrease in ice in the Bellingshausen and northern Weddell Seas.However,as the season transitions into summer,the ASL exerts a pronounced delayed effect,contributing to widespread sea ice loss across West Antarctica.Strong southerly winds on the western flank of the ASL push sea ice away from the inner Ross Sea,exposing coastal waters that absorb solar radiation,thereby accelerating ice melt through positive ice-albedo feedback.Simultaneously,northwesterly winds on the eastern flank transport warm air toward the Bellingshausen and northern Weddell Seas,intensifying ice loss in these regions.Furthermore,the active PSA is accompanied by a tripole sea surface temperature pattern characterized by warming in the Weddell Sea,which promotes continued ice melt.The co-occurrence of an exceptionally positive SAM,a La Niña,and a strong negative IOD during spring 2022,combined with lower-than-normal total spring SIE,ultimately contributed to the record-low Antarctic SIE observed in February 2023.
基金supported by the National Natural Science Foundation of China (No.22176148)the Shanghai Rising-Star Program (No.23QB1406400)+1 种基金the Fundamental Research Funds for the Central Universities of Tongji University (No.2023-3-ZD-02)supported by the program INTPART (Plastic Pollution,No.275172)funded by the Research Council of Norway.
文摘The ocean serves as a repository for various types of artificial nanoparticles.Nanoplastics(NPs)and nano zinc oxide(nZnO),which are frequently employed in personal care products and food packaging materials,are likely simultaneously released and eventually into the ocean with surface runoff.Therefore,their mutual influence and shared destiny in marine environment cannot be ignored.This study examined how nanomaterials interacted and transported through sea sand in various salinity conditions.Results showed that NPs remained dispersed in brine,while nZnO formed homoaggregates.In seawater of 35 practical salinity units(PSU),nZnO formed heteroaggregates with NPs,inhibiting NPs mobility and decreasing the recovered mass percentage(Meff)from 24.52%to 12.65%.In 3.5 PSU brackish water,nZnO did not significantly aggregate with NPs,and thus barely affected their mobility.However,NPs greatly enhanced nZnO transport with Meff increasing from 14.20%to 25.08%,attributed to the carrier effect of higher mobility NPs.Cotransport from brackishwater to seawater was simulated in salinity change experiments and revealed a critical salinity threshold of 10.4 PSU,below which the mobility of NPs was not affected by coexisting nZnO and above which nZnO strongly inhibited NP transport.This study highlights the importance of considering the mutual influence and shared destiny of artificial nanoparticles in the marine environment and how their interaction and cotransport are dependent on changes in seawater salinity.
基金supported by the National Natural Science Foundation of China(Grant No.42375024).
文摘As one of the strongest convection bands in the Southern Hemisphere,the South Pacific Convergence Zone(SPCZ)substantially influences the variabilities in the atmospheric circulation and Antarctic climate.In this study,it is revealed that the intensity of the SPCZ can change the characteristics of sea ice in the West Antarctica during austral autumn,which is significantly independent of the El Niño-Southern Oscillation(ENSO).Observational and numerical results suggest that a stronger-than-usual SPCZ can generate a poleward-propagating Rossby wave train along a great circular route and induce a weakening of the Amundsen Sea Low(ASL)near West Antarctica,which may somewhat offset the teleconnections exerted by ENSO.These changes in the strength and zonal extent of ASL is noticeable and robustly lead to a tripole response of sea-ice perturbations in the Ross,Amundsen,and Weddell Seas.We find that the wind-driven dynamical processes determine the local sea-ice changes,while the influence from thermodynamic processes is trivial.This research underscores the need to consider the SPCZ variability for a comprehensive understanding of sea-ice changes in West Antarctica on interannual timescales.
基金supported by the National Natural Science Foundation China(Grant No.42176222).
文摘As a crucial component of the Earth’s climate system,Antarctic sea ice has demonstrated significant variability over the satellite era.Here,we identify a remarkable decadal transition in the total Antarctic Sea Ice Extent(SIE).The stage from 1979 to 2006 is characterized by high-frequency(i.e.,seasonal to interannual)temporal variability in SIE and zonal asymmetry in Sea Ice Concentration(SIC),which is primarily under the control of the Amundsen Sea Low(ASL).After 2007,however,sea ice changes exhibit a more spatially homogeneous pattern in SIC and a more temporally long-lasting mode in SIE.Further analysis reveals that sea ice-ocean interaction plays a major role in the low-frequency(i.e.,multiannual)variability of Antarctic sea ice from 2007−22.The related physical process is inferred to manifest as a strong coupling between the surface and the subsurface ocean layers,involving enhanced vertical convection and the downward delivery of the surface anomalies related to ice melting and freezing processes,thus maintaining the SIE anomalies for a longer time.Furthermore,this process mainly occurs in the Amundsen-Bellingshausen Sea(ABS)sector,and the weakened subsurface ocean stratification is the key factor triggering the coupling process in this region.We find that the Circumpolar Deep Water(CDW)over the ABS sector continued to shoal before 2007 and remained stable thereafter.It is speculated that the shoaling of the CDW may be a possible driver leading to the weakening of the subsurface stratification.
基金supported by the National Natural Science Foundation of China(31201416)Programme of Introducing Talents of Discipline to Universities(B17018)。
文摘Hyperlipidemia constitutes a critical factor in the pathogenesis of vascular disease and gut microbiota dysbiosis.This study aims to investigate the role of sea buckthorn fruit oil(SBFO)in ameliorating hyperlipidemia,modulating gut microbiota,and elucidating the underlying mechanisms of its lipid-lowering effects.SBFO intervention in hyperlipidemic mice significantly reduced body weight and visceral adiposity index while mitigating symptoms associated with hyperlipidemia,including dyslipidemia,infla mmation,liver damage,and endothelial dysfunction.Real-time quantitative PCR and Western blot analyses revealed that SBFO enhanced the response of free fatty acid oxidation and breakdown(adenosine 5'-monophosphateactivated protein kinaseα,carnitine palmitoyltransferase1a,peroxisome proliferator-activated receptorα,and peroxisome proliferator-activated receptorγ)while suppressing the synthesis of triglycerides and fatty acids(sterol-regulatory element binding protein 1,fatty acid synthase,and acetyl CoA carboxylase)at the gene and protein expression levels.Moreover,SBFO intervention enriched the gut microbiota of hyperlipidemic mice by increasing the relative abundances of Lactobacillus,Faecalibaculum,and Allobaculum,while decreasing the Firmicutes/Bacteroidetes ratio.These findings suggest that SBFO exhibits promising therapeutic potential in attenuating hyperlipidemia in mice through the regulation of lipid metabolism and modulation of gut microbiota.
基金Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)National Natural Science Foundation of China(42475003)Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(SML2023SP209)。
文摘Southerly moisture surges over the central South China Sea(SCS)are characterized by the strengthening of lowlevel southerlies that transport moisture northward from the Pacific or Indian Oceans to South China.These surge events typically occur for days in the early-summer season(from April to June)and can lead to heavy rains in South China.This study categorizes surge events into three types of flow patterns and examines their multiscale variations and impacts on rainfall.The first type occurs mainly in April,with the southeasterlies enhanced by a deepening trough in South China and the western Pacific subtropical high established over the SCS.The second type of surge events mostly appears in June,featuring the prevailing southwesterlies of summer monsoon from the Indian Ocean during the active phases of intraseasonal oscillations.Most surge events exhibit semi-diurnal variations with morning and afternoon peaks of northward moisture fluxes.Specifically,the first type features a dominant afternoon peak,while the second type shows a dominant early-morning peak,which is induced by thermal contrast between the Indochina Peninsula and the SCS.In general,the surge events enhance moisture convergence and increase rainfall downstream in South China,but they show some regional differences.The second type strengthens moisture convergence and rainfall in coastal regions with a morning peak.In contrast,the first type enhances inland rainfall with a morning peak,while moisture divergence dominates coastal regions.The third type of surge events denotes transitional conditions between the first two types,in terms of atmospheric circulations,diurnal cycles,and rainfall patterns.These results highlight a diversity of regional moisture surges and related rainfall ranging from diurnal to sub-seasonal scales.
基金funded by the South Oil Exploration and Development Company of PetroChina(2021-HNYJ-010).
文摘The Fushan Depression is one of the petroliferous depressions in the Beibuwan Basin,South China Sea.Previous studies have preliminarily explored the origin and source of crude oils in some areas of this depression.Nevertheless,no systematic investigations on the classification and origin of oils and hy-drocarbon migration processes have been made for the entire petroleum system in this depression,which has significantly hindered the hydrocarbon exploration in the region.A total of 32 mudstone and 58 oil samples from the Fushan Depression were analyzed to definite the detailed oil-source correlation within the sequence and sedimentary framework.The organic matter of third member of Paleogene Liushagang Formation(Els(3))source rocks,both deltaic and lacustrine mudstone,are algal-dominated with high abundance of C_(23)tricyclic terpane and C_(30)4-methylsteranes.The deltaic source rocks occur-ring in the first member(Els_(1))and second member(Els_(2))of the Paleogene Liushagang Formation are characterized by high abundance of C_(19+20)tricyclic terpane and oleanane,reflecting a more terrestrial plants contribution.While lacustrine source rocks of Els_(1)and Els_(2)display the reduced input of terrige-nous organic matter with relatively low abundance of C 19+20 tricyclic terpane and oleanane.Three types of oils were identified by their biomarker compositions in this study.Most of the oils discovered in the Huachang and Bailian Els_(1)reservoir belong to group A and were derived from lacustrine source rocks of Els_(1)and Els_(2).Group B oils are found within the Els_(1)and Els_(2)reservoirs,showing a close relation to the deltaic source rocks of Els_(1)and Els_(2),respectively.Group C oils,occurring in the Els3 reservoirs,have a good affinity with the Els3 source rocks.The spatial distribution and accumulation of different groups of oils are mainly controlled by the sedimentary facies and specific structural conditions.The Els_(2)reservoir in the Yong'an area belonging to Group B oil,are adjacent to the source kitchen and could be considered as the favorable exploration area in the future.
基金supported by the National Nat-ural Science Foundation of China(No.42376174)the Natural Science Foundation of Shanghai(No.23ZR 1426900).
文摘Synthetic aperture radar(SAR)aboard SEASAT was first launched in 1978.At the beginning of the 21st century,the Chinese remote sensing community recognized the urgent need to develop domestic SAR capabilities.Unlike scatterometers and al-timeters,space-borne SAR offers high-resolution images of the ocean,regardless of weather conditions or time of day.SAR imagery provides rich information about the sea surface,capturing complicated dynamic processes in the upper layers of the ocean,particular-ly in relation to tropical cyclones.Over the past four decades,the advantages of SAR have been increasingly recognized,leading to notable marine applications,especially in the development of algorithms for retrieving wind and wave data from SAR images.This study reviews the history,progress,and future outlook of SAR-based monitoring of sea surface wind and waves.In particular,the ap-plicability of various SAR wind and wave algorithms is systematically investigated,with a particular focus on their performance un-der extreme sea conditions.
