Revealing regional climate changes is vital for policymaking activities related to climate change adaptation and mitigation.South China is a well-developed region with a dense population,but the level of uncertainty i...Revealing regional climate changes is vital for policymaking activities related to climate change adaptation and mitigation.South China is a well-developed region with a dense population,but the level of uncertainty in climate projections remains to be evaluated in detail.In this study,we comprehensively assessed the historical simulations and future projections of climate change in South China based on CMIP5/CMIP6 models.We show evidence that CMIP5/CMIP6 models can skillfully reproduce the observed distributions of annual/seasonal mean temperature but show much lower skill for precipitation.CMIP6 outperforms CMIP5 in the historical simulations,as evidenced by more models with lower bias magnitude and higher skill scores.During 2021–2100,the annual mean temperature over South China is projected to increase significantly at a rate of 0.53(0.42–0.63)and 0.59(0.52–0.66)℃(10 yr)^(-1),while precipitation is projected to increase slightly at a rate of 0.78(0.15–1.56)and 1.52(0.91–2.30)%(10 yr)^(-1),under the RCP8.5 and SSP5-8.5 scenarios,respectively.CMIP6 models project larger annual/seasonal mean temperature and precipitation trends than CMIP5 models under equivalent scenarios.The temperature in South China is projected to increase robustly by more than1.5℃during 2041–2060 under RCP4.5 and SSP2-4.5,but by 4.5℃during 2081–2100,under RCP8.5 and SSP5-8.5 with respect to 1850–1900.The uncertainty in temperature projections is mainly dominated by model uncertainty and scenario uncertainty,while internal uncertainty contributes some of the uncertainty during the near-term.The uncertainty in precipitation projection stems mainly from internal uncertainty and model uncertainty.For both the temperature and precipitation projection uncertainty,the relative sizes of contributions from the main contributors vary with time and show obvious seasonal differences.展开更多
A prior observational study indicated an asymmetric link between sea surface temperature(SST)in the Tasman Sea and ENSO during austral summer.Specifically,El Niño is associated with a dipolar SST anomaly pattern,...A prior observational study indicated an asymmetric link between sea surface temperature(SST)in the Tasman Sea and ENSO during austral summer.Specifically,El Niño is associated with a dipolar SST anomaly pattern,featuring warming in the northwest and cooling in the southeast,whereas La Niña corresponds to basin-scale warming.This study employs the experiments of coupled models from the sixth phase of the Coupled Model Intercomparison Project(CMIP6)to assess ENSO’s impact on Tasman Sea SST.While all 15 models capture the observed dipolar SST anomalies(SSTAs)in the Tasman Sea during El Niño years,only 7 models capture the basin-scale warmth in the Tasman Sea during La Niña years.Consequently,the models are bifurcated into two groups:group-one models yield one physically reasonable asymmetric connection as observed,including the asymmetry of oceanic heat transport,especially the Ekman meridional transport anomalies induced by zonal wind stress driven by the asymmetric atmospheric circulation over the Tasman Sea.However,due to abnormal responses to ENSO and systematic biases in model simulations,including jet and storm tracks,oceanic heat fluxes,ocean currents,and SST,the group-two models fail to reproduce the asymmetric connection between the Tasman Sea and ENSO.This study not only validates the observational asymmetric connection of SSTAs in the Tasman Sea with respect to the two opposite ENSO phases,but also provides evidence and clues to reduce the bias in group-two models.展开更多
The magnitude of El Nino determines the level of its global impact.Yet,how well our state-of-the-art models simulate this key aspect of El Nino is not well documented.Previous studies tend to ignore El Nino-Southern O...The magnitude of El Nino determines the level of its global impact.Yet,how well our state-of-the-art models simulate this key aspect of El Nino is not well documented.Previous studies tend to ignore El Nino-Southern Oscillation(ENSO)asymmetry and equate the variance of ENSO to the magnitude of El Nino.Moreover,previous evaluations are more focused on the surface manifestation of El Nino.Here,we quantify the magnitudes of El Nino and La Nina separately,both at the surface and subsurface levels.At the surface,we find that while the magnitude of La Nina events in most models is generally stronger than observed,the magnitude of El Nino is more diverse to observations.In fact,in many models,El Nino is weaker than observed.This bias in the magnitude of El Nino is more pronounced in the subsurface.We attribute this weakness in the subsurface to the generally weaker coupling strength and the apparent stronger ENSO at the surface to a lack of sufficiently strong negative feedback from the surface heat flux in the models.When normalized by the variance of ENSO,the lack of exceptionally strong El Nino events in the models is more common and pronounced.We further studied the lifespan of El Nino and La Nina events and have found that multi-year duration is not confined to just La Nina events.There are also El Nino events that last more than one year.Moreover,we have found that multi-year long La Nina events tend to occur over the decades with strong El Nino events.The study also briefly explores the impact of global warming on the duration of ENSO events through the use of a simple model and simulations by CMIP6 models.It has been found that the frequency of multi-year El Nino and La Nina events increases with global warming.展开更多
Against the backdrop of climate change,the activity of tropical cyclones(TCs)has captured widespread attention.Observational datasets indicate a declining trend in the genesis longitude of western North Pacific(WNP)TC...Against the backdrop of climate change,the activity of tropical cyclones(TCs)has captured widespread attention.Observational datasets indicate a declining trend in the genesis longitude of western North Pacific(WNP)TCs.This study investigates the zonal changes of WNP TCs with CMIP6-HighResMIP models.These models capture the genesis density of WNP TCs fairly well.The results reveal a westward shift in TC genesis longitude.This trend is associated with the significant reduction in the TC frequency over the southeastern WNP.The study also discusses changes in large-scale circulation patterns and the impact of the strengthening Pacific Walker circulation.展开更多
Pronounced climatic differences occur over subtropical South China(SC)and tropical South China Sea(SCS)and understanding the key cloud-radiation characteristics is essential to simulating East Asian climate.This study...Pronounced climatic differences occur over subtropical South China(SC)and tropical South China Sea(SCS)and understanding the key cloud-radiation characteristics is essential to simulating East Asian climate.This study investigated cloud fractions and cloud radiative effects(CREs)over SC and SCS simulated by CMIP6 atmospheric models.Remarkable differences in cloud-radiation characteristics appeared over these two regions.In observations,considerable amounts of low-middle level clouds and cloud radiative cooling effect appeared over SC.In contrast,high clouds prevailed over SCS,where longwave and shortwave CREs offset each other,resulting in a weaker net cloud radiative effect(NCRE).The models underestimated NCRE over SC mainly due to weaker shortwave CRE and less cloud fractions.Conversely,most models overestimated NCRE over SCS because of stronger shortwave CRE and weaker longwave CRE.Regional CREs were closely linked to their dominant cloud fractions.Both observations and simulations showed a negative spatial correlation between total(low)cloud fraction and shortwave CRE over SC,especially in winter,and exhibited a positive correlation between high cloud fraction and longwave CRE over these two regions.Compared with SCS,most models overestimated the spatial correlation between low(high)cloud fraction and SWCRE(LWCRE)over SC,with larger bias ranges among models,indicating the exaggerated cloud radiative cooling(warming)effect caused by low(high)clouds.Moreover,most models struggled to describe regional ascent and its connection with CREs over SC while they can better reproduce these connections over SCS.This study further suggests that reasonable circulation conditions are crucial to simulating well cloud-radiation characteristics over the East Asian regions.展开更多
Due to the different microstructures caused by the heat source effect,welding joints exhibit significant differences in mechanical properties compared to the base material.Precise characterization of the constitutive ...Due to the different microstructures caused by the heat source effect,welding joints exhibit significant differences in mechanical properties compared to the base material.Precise characterization of the constitutive characteristics of the welded joint requires a large number of repetitive experiments,which are costly,inefficient,and have limited accuracy improvements.This paper proposes an integrated experimental-simulation-based inverse calibration method,which establishes a calibration optimization problem based on the corresponding constitutive model and a finite element calculation model built by the distribution of hardness in the weldment.Using the global tensile force-displacement curve of the MIG-welded 6005A-T6 aluminum alloy specimen and the experimental data of local deformation with time change obtained from DIC(Digital Image Correlation),the parameters involved in the constitutive models are optimized accordingly.This method can directly obtain the constitutive characteristics of the weldment under conditions of limited experiments and insufficient data.Additionally,the adaptability of the constitutive model to the calibration method and the influence of optimization results are discussed and analyzed.The results indicate that the global force-displacement response of the non-saturated Ramberg-Osgood(R-O)model is in the best agreement with that of the experimental data,and the energy error is only 2.62%,followed by the MPL model,while the saturation-based Voce model shows the largest simulation error in terms of the presented object.Furthermore,the simulation results of R-O,Voce,and MPL models in the local area are far superior to traditional fitting methods.展开更多
A novel digital twin(DT)enabled channel model for 6G vehicular communications in Beijing Central Business District(Beijing CBD)is proposed,which can support the design of intelligent transportation systems(ITSs).A DT ...A novel digital twin(DT)enabled channel model for 6G vehicular communications in Beijing Central Business District(Beijing CBD)is proposed,which can support the design of intelligent transportation systems(ITSs).A DT space for Beijing CBD is constructed,and two typical transportation periods,i.e.,peak and off-peak hours,are considered to characterize the vehicular communication channel better.Based on the constructed DT space,a DT-enabled vehicular communication dataset is developed,including light detection and ranging(LiDAR)point clouds,RGB images,and channel information.With the assistance of LiDAR point clouds and RGB images,the scatterer parameters,including number,distance,angle,power,and velocity,are analyzed under different transportation periods.The channel non-stationarity and consistency are mimicked in the proposed model.The key channel statistical properties are derived and simulated.Compared to ray-tracing(RT)results,the accuracy of the proposed model is verified.展开更多
In Saharan climates,greenhouses face extreme diurnal temperature fluctuations that generate thermal stress,reduce crop productivity,and hinder sustainable agricultural practices.Passive thermal storage using Phase Cha...In Saharan climates,greenhouses face extreme diurnal temperature fluctuations that generate thermal stress,reduce crop productivity,and hinder sustainable agricultural practices.Passive thermal storage using Phase Change Materials(PCM)is a promising solution to stabilize microclimatic conditions.This study aims to evaluate experimentally and numerically the effectiveness of PCM integration for moderating greenhouse temperature fluctuations under Saharan climatic conditions.Two identical greenhouse prototypes were constructed in Ghardaia,Algeria:a reference greenhouse and a PCM-integrated greenhouse using calcium chloride hexahydrate(CaCl_(2)⋅6H_(2)O).Thermal performance was assessed during a five-day experimental period(7–11May 2025)under severe ambient conditions.To complement this,a Nonlinear Auto-Regressive with eXogenous inputs(NARX)neural network model was developed and trained using a larger dataset(7–25 May 2025)to predict greenhouse thermal dynamics.The PCM greenhouse reduced peak daytime air temperature by an average of 8.14℃and decreased the diurnal temperature amplitude by 53.6%compared to the reference greenhouse.The NARX model achieved high predictive accuracy(R^(2)=0.990,RMSE=0.425℃,MAE=0.223℃,MBE=0.008℃),capturing both sensible and latent heat transfer mechanisms,including PCM melting and solidification.The combined experimental and predictive modeling results confirm the potential of PCM integration as an effective passive thermal regulation strategy for greenhouses in arid regions.This approach enhances microclimatic stability,improves energy efficiency,and supports the sustainability of protected agriculture under extreme climatic conditions.展开更多
A“water”accelerated metal-free catalytic system has been discovered for the Mukaiyama-aldol reaction.The system involves the use of B(C_(6)F_(5))_(3) as a catalyst,which is water-tolerant and able to activate the ca...A“water”accelerated metal-free catalytic system has been discovered for the Mukaiyama-aldol reaction.The system involves the use of B(C_(6)F_(5))_(3) as a catalyst,which is water-tolerant and able to activate the carbonyl group through a hydrogen bonding network generated by the catalyst.This activation method allows the reactions to be performed with very low catalyst loading,as low as 0.5 mol%.The scope of substrates is broad and a wide variety of functional groups are well tolerated.Diverse aliphatic aldehydes,aromatic aldehydes,unsaturated aldehydes and aromatic ketones coupled with silyl enol ethers/silyl ketone acetals to generate their correspondingβ-hydroxy carbonyl compounds in moderate to good yields.This discovery represents a significant advancement in the field of organic synthesis,as it provides a new,practical and sustainable solution for carbon-carbon bond formation in water.展开更多
Both the attribution of historical change and future projections of droughts rely heavily on climate modeling. However,reasonable drought simulations have remained a challenge, and the related performances of the curr...Both the attribution of historical change and future projections of droughts rely heavily on climate modeling. However,reasonable drought simulations have remained a challenge, and the related performances of the current state-of-the-art Coupled Model Intercomparison Project phase 6(CMIP6) models remain unknown. Here, both the strengths and weaknesses of CMIP6 models in simulating droughts and corresponding hydrothermal conditions in drylands are assessed.While the general patterns of simulated meteorological elements in drylands resemble the observations, the annual precipitation is overestimated by ~33%(with a model spread of 2.3%–77.2%), along with an underestimation of potential evapotranspiration(PET) by ~32%(17.5%–47.2%). The water deficit condition, measured by the difference between precipitation and PET, is 50%(29.1%–71.7%) weaker than observations. The CMIP6 models show weaknesses in capturing the climate mean drought characteristics in drylands, particularly with the occurrence and duration largely underestimated in the hyperarid Afro-Asian areas. Nonetheless, the drought-associated meteorological anomalies, including reduced precipitation, warmer temperatures, higher evaporative demand, and increased water deficit conditions, are reasonably reproduced. The simulated magnitude of precipitation(water deficit) associated with dryland droughts is overestimated by 28%(24%) compared to observations. The observed increasing trends in drought fractional area,occurrence, and corresponding meteorological anomalies during 1980–2014 are reasonably reproduced. Still, the increase in drought characteristics, associated precipitation and water deficit are obviously underestimated after the late 1990s,especially for mild and moderate droughts, indicative of a weaker response of dryland drought changes to global warming in CMIP6 models. Our results suggest that it is imperative to employ bias correction approaches in drought-related studies over drylands by using CMIP6 outputs.展开更多
The diurnal temperature range(DTR)serves as a vital indicator reflecting both natural climate variability and anthropogenic climate change.This study investigates the historical and projected multitemporal DTR variati...The diurnal temperature range(DTR)serves as a vital indicator reflecting both natural climate variability and anthropogenic climate change.This study investigates the historical and projected multitemporal DTR variations over the Tibetan Plateau.It assesses 23 climate models from phase 6 of the Coupled Model Intercomparison Project(CMIP6)using CN05.1 observational data as validation,evaluating their ability to simulate DTR over the Tibetan Plateau.Then,the evolution of DTR over the Tibetan Plateau under different shared socioeconomic pathway(SSP)scenarios for the near,middle,and long term of future projection are analyzed using 11 selected robustly performing models.Key findings reveal:(1)Among the models examined,BCC-CSM2-MR,EC-Earth3,EC-Earth3-CC,EC-Earth3-Veg,EC-Earth3-Veg-LR,FGOALS-g3,FIO-ESM-2-0,GFDL-ESM4,MPI-ESM1-2-HR,MPI-ESM1-2-LR,and INM-CM5-0 exhibit superior integrated simulation capability for capturing the spatiotemporal variability of DTR over the Tibetan Plateau.(2)Projection indicates a slightly increasing trend in DTR on the Tibetan Plateau in the SSP1-2.6 scenario,and decreasing trends in the SSP2-4.5,SSP3-7.0,and SPP5-8.5 scenarios.In certain areas,such as the southeastern edge of the Tibetan Plateau,western hinterland of the Tibetan Plateau,southern Kunlun,and the Qaidam basins,the changes in DTR are relatively large.(3)Notably,the warming rate of maximum temperature under SSP2-4.5,SSP3-7.0,and SPP5-8.5 is slower compared to that of minimum temperature,and it emerges as the primary contributor to the projected decrease in DTR over the Tibetan Plateau in the future.展开更多
Background:The active components of Horcha-6 were identified using liquid chromatography with tandem mass spectrometry.Also,we investigated the potential mechanisms that explain why Horcha-6 may be effective in treati...Background:The active components of Horcha-6 were identified using liquid chromatography with tandem mass spectrometry.Also,we investigated the potential mechanisms that explain why Horcha-6 may be effective in treating migraines through the use of network pharmacology and a rat migraine model.Methods:After identifying the active components of Horcha-6,the corresponding genes of the active components’target were obtained from the Universal Protein database,and a“compound-target-disease”network was constructed using Cytoscape 3.9.0 software.For the in vivo experiments,nitroglycerin was injected intraperitoneally into rats to create a migraine model.Pre-treatment with Horcha-6 was administered orally for 14 days,and rats were subjected to migraine-related behavior tests.RNA sequencing was performed to identify the gene expression regulated by Horcha-6 in the trigeminal nerve.Results:A total of 903 chemical components of Horcha-6 have been collected in the liquid chromatography with tandem mass spectrometry.We discovered 55 of the Horcha-6 bio-active components that were evaluated based on their Percent Human Oral Absorption(≥30%)and DL values(≥0.185)on the traditional Chinese medicine systems pharmacology database.The“compound-target-disease”network contained 163 intersection targets with the migraine state.Gene Ontology analysis indicated that these components significantly regulated the immune response,vascular function,oxidative stress,etc.When Kyoto Encyclopedia of Genes and Genomes enrichment analysis was performed,we observed that most of the target genes were significantly enriched in the inflammation and neuro-related signaling pathway,toll-like receptor signaling pathway,neuroactive ligand-receptor interaction,etc.These predictions were further demonstrated via in vivo animal model experiments.The RNA sequencing results showed that 41 genes were down-regulated(P<0.05)and 86 genes were up-regulated(P<0.05)in the Horcha-6 treated group compared with the untreated group.Those genes were mainly involved in neuromodulation,vascular function,and hormone metabolism.Conclusion:The 55 bio-active components in Horcha-6 regulate inflammation,hormone metabolism,and neurotransmitters and have potential as a therapy to treat migraines.展开更多
Future 6G communications are envisioned to enable a large catalogue of pioneering applications.These will range from networked Cyber-Physical Systems to edge computing devices,establishing real-time feedback control l...Future 6G communications are envisioned to enable a large catalogue of pioneering applications.These will range from networked Cyber-Physical Systems to edge computing devices,establishing real-time feedback control loops critical for managing Industry 5.0 deployments,digital agriculture systems,and essential infrastructures.The provision of extensive machine-type communications through 6G will render many of these innovative systems autonomous and unsupervised.While full automation will enhance industrial efficiency significantly,it concurrently introduces new cyber risks and vulnerabilities.In particular,unattended systems are highly susceptible to trust issues:malicious nodes and false information can be easily introduced into control loops.Additionally,Denialof-Service attacks can be executed by inundating the network with valueless noise.Current anomaly detection schemes require the entire transformation of the control software to integrate new steps and can only mitigate anomalies that conform to predefined mathematical models.Solutions based on an exhaustive data collection to detect anomalies are precise but extremely slow.Standard models,with their limited understanding of mobile networks,can achieve precision rates no higher than 75%.Therefore,more general and transversal protection mechanisms are needed to detect malicious behaviors transparently.This paper introduces a probabilistic trust model and control algorithm designed to address this gap.The model determines the probability of any node to be trustworthy.Communication channels are pruned for those nodes whose probability is below a given threshold.The trust control algorithmcomprises three primary phases,which feed themodel with three different probabilities,which are weighted and combined.Initially,anomalous nodes are identified using Gaussian mixture models and clustering technologies.Next,traffic patterns are studied using digital Bessel functions and the functional scalar product.Finally,the information coherence and content are analyzed.The noise content and abnormal information sequences are detected using a Volterra filter and a bank of Finite Impulse Response filters.An experimental validation based on simulation tools and environments was carried out.Results show the proposed solution can successfully detect up to 92%of malicious data injection attacks.展开更多
The subtropical North and South Pacific Meridional Modes(NPMM and SPMM)are well known precursors of El Niño-Southern Oscillation(ENSO).However,relationship between them is not constant.In the early 1980,the relat...The subtropical North and South Pacific Meridional Modes(NPMM and SPMM)are well known precursors of El Niño-Southern Oscillation(ENSO).However,relationship between them is not constant.In the early 1980,the relationship experienced an interdecadal transition.Changes in this connection can be attributed mainly to the phase change of the Pacific decadal oscillation(PDO).During the positive phase of PDO,a shallower thermocline in the central Pacific is responsible for the stronger trade wind charging(TWC)mechanism,which leads to a stronger equatorial subsurface temperature evolution.This dynamic process strengthens the connection between NPMM and ENSO.Associated with the negative phase of PDO,a shallower thermocline over southeastern Pacific allows an enhanced wind-evaporation-SST(WES)feedback,strengthening the connection between SPMM and ENSO.Using 35 Coupled Model Intercomparison Project Phase 6(CMIP6)models,we examined the NPMM/SPMM performance and its connection with ENSO in the historical runs.The great majority of CMIP6 models can reproduce the pattern of NPMM and SPMM well,but they reveal discrepant ENSO and NPMM/SPMM relationship.The intermodal uncertainty for the connection of NPMM-ENSO is due to different TWC mechanism.A stronger TWC mechanism will enhance NPMM forcing.For SPMM,few models can simulate a good relationship with ENSO.The intermodel spread in the relationship of SPMM and ENSO owing to SST bias in the southeastern Pacific,as WES feedback is stronger when the southeastern Pacific is warmer.展开更多
基金jointly supported by the Joint Funds of the National Natural Science Foundation of China(Grant No.U2242203)the National Natural Science Foundation of China(Grant No.41905070)+4 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2021A1515011421,2023A1515240067,2023B1515020009)the National Key R&D Program of China(Grant No.2018YFC1505801)supported by the Guangdong Provincial Marine Meteorology Science Data Center(2024B1212070014)the China Meteorology Administration Key Innovation Team of Tropical Meteorology(Grant No.CMA2023ZD08)State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences(Project No.LTO2311)。
文摘Revealing regional climate changes is vital for policymaking activities related to climate change adaptation and mitigation.South China is a well-developed region with a dense population,but the level of uncertainty in climate projections remains to be evaluated in detail.In this study,we comprehensively assessed the historical simulations and future projections of climate change in South China based on CMIP5/CMIP6 models.We show evidence that CMIP5/CMIP6 models can skillfully reproduce the observed distributions of annual/seasonal mean temperature but show much lower skill for precipitation.CMIP6 outperforms CMIP5 in the historical simulations,as evidenced by more models with lower bias magnitude and higher skill scores.During 2021–2100,the annual mean temperature over South China is projected to increase significantly at a rate of 0.53(0.42–0.63)and 0.59(0.52–0.66)℃(10 yr)^(-1),while precipitation is projected to increase slightly at a rate of 0.78(0.15–1.56)and 1.52(0.91–2.30)%(10 yr)^(-1),under the RCP8.5 and SSP5-8.5 scenarios,respectively.CMIP6 models project larger annual/seasonal mean temperature and precipitation trends than CMIP5 models under equivalent scenarios.The temperature in South China is projected to increase robustly by more than1.5℃during 2041–2060 under RCP4.5 and SSP2-4.5,but by 4.5℃during 2081–2100,under RCP8.5 and SSP5-8.5 with respect to 1850–1900.The uncertainty in temperature projections is mainly dominated by model uncertainty and scenario uncertainty,while internal uncertainty contributes some of the uncertainty during the near-term.The uncertainty in precipitation projection stems mainly from internal uncertainty and model uncertainty.For both the temperature and precipitation projection uncertainty,the relative sizes of contributions from the main contributors vary with time and show obvious seasonal differences.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFF0805101)the National Natural Science Founda-tion of China(Grant Nos.42376250 and 42405068).
文摘A prior observational study indicated an asymmetric link between sea surface temperature(SST)in the Tasman Sea and ENSO during austral summer.Specifically,El Niño is associated with a dipolar SST anomaly pattern,featuring warming in the northwest and cooling in the southeast,whereas La Niña corresponds to basin-scale warming.This study employs the experiments of coupled models from the sixth phase of the Coupled Model Intercomparison Project(CMIP6)to assess ENSO’s impact on Tasman Sea SST.While all 15 models capture the observed dipolar SST anomalies(SSTAs)in the Tasman Sea during El Niño years,only 7 models capture the basin-scale warmth in the Tasman Sea during La Niña years.Consequently,the models are bifurcated into two groups:group-one models yield one physically reasonable asymmetric connection as observed,including the asymmetry of oceanic heat transport,especially the Ekman meridional transport anomalies induced by zonal wind stress driven by the asymmetric atmospheric circulation over the Tasman Sea.However,due to abnormal responses to ENSO and systematic biases in model simulations,including jet and storm tracks,oceanic heat fluxes,ocean currents,and SST,the group-two models fail to reproduce the asymmetric connection between the Tasman Sea and ENSO.This study not only validates the observational asymmetric connection of SSTAs in the Tasman Sea with respect to the two opposite ENSO phases,but also provides evidence and clues to reduce the bias in group-two models.
基金The National Natural Science Foundation of China under contract No.42250710154。
文摘The magnitude of El Nino determines the level of its global impact.Yet,how well our state-of-the-art models simulate this key aspect of El Nino is not well documented.Previous studies tend to ignore El Nino-Southern Oscillation(ENSO)asymmetry and equate the variance of ENSO to the magnitude of El Nino.Moreover,previous evaluations are more focused on the surface manifestation of El Nino.Here,we quantify the magnitudes of El Nino and La Nina separately,both at the surface and subsurface levels.At the surface,we find that while the magnitude of La Nina events in most models is generally stronger than observed,the magnitude of El Nino is more diverse to observations.In fact,in many models,El Nino is weaker than observed.This bias in the magnitude of El Nino is more pronounced in the subsurface.We attribute this weakness in the subsurface to the generally weaker coupling strength and the apparent stronger ENSO at the surface to a lack of sufficiently strong negative feedback from the surface heat flux in the models.When normalized by the variance of ENSO,the lack of exceptionally strong El Nino events in the models is more common and pronounced.We further studied the lifespan of El Nino and La Nina events and have found that multi-year duration is not confined to just La Nina events.There are also El Nino events that last more than one year.Moreover,we have found that multi-year long La Nina events tend to occur over the decades with strong El Nino events.The study also briefly explores the impact of global warming on the duration of ENSO events through the use of a simple model and simulations by CMIP6 models.It has been found that the frequency of multi-year El Nino and La Nina events increases with global warming.
基金supported by a key project of the National Natural Science Foundation of China[grant number 42192563]。
文摘Against the backdrop of climate change,the activity of tropical cyclones(TCs)has captured widespread attention.Observational datasets indicate a declining trend in the genesis longitude of western North Pacific(WNP)TCs.This study investigates the zonal changes of WNP TCs with CMIP6-HighResMIP models.These models capture the genesis density of WNP TCs fairly well.The results reveal a westward shift in TC genesis longitude.This trend is associated with the significant reduction in the TC frequency over the southeastern WNP.The study also discusses changes in large-scale circulation patterns and the impact of the strengthening Pacific Walker circulation.
基金Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)National Natural Science Foundation of China(72293604,42275026)Open Grants of the State Key Laboratory of Severe Weather(2023LASW-B09)。
文摘Pronounced climatic differences occur over subtropical South China(SC)and tropical South China Sea(SCS)and understanding the key cloud-radiation characteristics is essential to simulating East Asian climate.This study investigated cloud fractions and cloud radiative effects(CREs)over SC and SCS simulated by CMIP6 atmospheric models.Remarkable differences in cloud-radiation characteristics appeared over these two regions.In observations,considerable amounts of low-middle level clouds and cloud radiative cooling effect appeared over SC.In contrast,high clouds prevailed over SCS,where longwave and shortwave CREs offset each other,resulting in a weaker net cloud radiative effect(NCRE).The models underestimated NCRE over SC mainly due to weaker shortwave CRE and less cloud fractions.Conversely,most models overestimated NCRE over SCS because of stronger shortwave CRE and weaker longwave CRE.Regional CREs were closely linked to their dominant cloud fractions.Both observations and simulations showed a negative spatial correlation between total(low)cloud fraction and shortwave CRE over SC,especially in winter,and exhibited a positive correlation between high cloud fraction and longwave CRE over these two regions.Compared with SCS,most models overestimated the spatial correlation between low(high)cloud fraction and SWCRE(LWCRE)over SC,with larger bias ranges among models,indicating the exaggerated cloud radiative cooling(warming)effect caused by low(high)clouds.Moreover,most models struggled to describe regional ascent and its connection with CREs over SC while they can better reproduce these connections over SCS.This study further suggests that reasonable circulation conditions are crucial to simulating well cloud-radiation characteristics over the East Asian regions.
基金Supported by National Natural Science Foundation of China(Grant Nos.52202431,52172353)Talent Fund of Beijing Jiaotong University of China(Grant No.2024XKRC044).
文摘Due to the different microstructures caused by the heat source effect,welding joints exhibit significant differences in mechanical properties compared to the base material.Precise characterization of the constitutive characteristics of the welded joint requires a large number of repetitive experiments,which are costly,inefficient,and have limited accuracy improvements.This paper proposes an integrated experimental-simulation-based inverse calibration method,which establishes a calibration optimization problem based on the corresponding constitutive model and a finite element calculation model built by the distribution of hardness in the weldment.Using the global tensile force-displacement curve of the MIG-welded 6005A-T6 aluminum alloy specimen and the experimental data of local deformation with time change obtained from DIC(Digital Image Correlation),the parameters involved in the constitutive models are optimized accordingly.This method can directly obtain the constitutive characteristics of the weldment under conditions of limited experiments and insufficient data.Additionally,the adaptability of the constitutive model to the calibration method and the influence of optimization results are discussed and analyzed.The results indicate that the global force-displacement response of the non-saturated Ramberg-Osgood(R-O)model is in the best agreement with that of the experimental data,and the energy error is only 2.62%,followed by the MPL model,while the saturation-based Voce model shows the largest simulation error in terms of the presented object.Furthermore,the simulation results of R-O,Voce,and MPL models in the local area are far superior to traditional fitting methods.
基金supported in part by the National Natural Science Foundation of China under Grant Nos.62371273,62125101 and 62341101the Taishan Scholars Program under Grant No.tsqn202312307+7 种基金the Young Elite Scientists Sponsorship Program by CAST under Grant No.YESS20230372the Shandong Natural Science Foundation under Grant No.ZR2023YQ058the New Cornerstone Science Foundation through the Xplorer Prizethe Xiaomi Young Talents Programthe open research fund of National Mobile Communications Research Laboratory,Southeast University under Grant No.2025D04the China National Postdoctoral Program for Innovative Talents under Grant No.BX20240007the China Postdoctoral Science Foundation under Grant No.2024M760111the Beijing Natural Science Foundation under Grant No.4254067。
文摘A novel digital twin(DT)enabled channel model for 6G vehicular communications in Beijing Central Business District(Beijing CBD)is proposed,which can support the design of intelligent transportation systems(ITSs).A DT space for Beijing CBD is constructed,and two typical transportation periods,i.e.,peak and off-peak hours,are considered to characterize the vehicular communication channel better.Based on the constructed DT space,a DT-enabled vehicular communication dataset is developed,including light detection and ranging(LiDAR)point clouds,RGB images,and channel information.With the assistance of LiDAR point clouds and RGB images,the scatterer parameters,including number,distance,angle,power,and velocity,are analyzed under different transportation periods.The channel non-stationarity and consistency are mimicked in the proposed model.The key channel statistical properties are derived and simulated.Compared to ray-tracing(RT)results,the accuracy of the proposed model is verified.
文摘In Saharan climates,greenhouses face extreme diurnal temperature fluctuations that generate thermal stress,reduce crop productivity,and hinder sustainable agricultural practices.Passive thermal storage using Phase Change Materials(PCM)is a promising solution to stabilize microclimatic conditions.This study aims to evaluate experimentally and numerically the effectiveness of PCM integration for moderating greenhouse temperature fluctuations under Saharan climatic conditions.Two identical greenhouse prototypes were constructed in Ghardaia,Algeria:a reference greenhouse and a PCM-integrated greenhouse using calcium chloride hexahydrate(CaCl_(2)⋅6H_(2)O).Thermal performance was assessed during a five-day experimental period(7–11May 2025)under severe ambient conditions.To complement this,a Nonlinear Auto-Regressive with eXogenous inputs(NARX)neural network model was developed and trained using a larger dataset(7–25 May 2025)to predict greenhouse thermal dynamics.The PCM greenhouse reduced peak daytime air temperature by an average of 8.14℃and decreased the diurnal temperature amplitude by 53.6%compared to the reference greenhouse.The NARX model achieved high predictive accuracy(R^(2)=0.990,RMSE=0.425℃,MAE=0.223℃,MBE=0.008℃),capturing both sensible and latent heat transfer mechanisms,including PCM melting and solidification.The combined experimental and predictive modeling results confirm the potential of PCM integration as an effective passive thermal regulation strategy for greenhouses in arid regions.This approach enhances microclimatic stability,improves energy efficiency,and supports the sustainability of protected agriculture under extreme climatic conditions.
基金financial support from the Start-up Grant of Nanjing Tech University(Nos.38274017103,38037037)financial support from Distinguished University Professor grant(Nanyang Technological University)+1 种基金the Agency for Science,Technology and Research(A∗STAR)under its MTC Individual Research Grants(No.M21K2c0114)RIE2025 MTC Programmatic Fund(No.M22K9b0049).
文摘A“water”accelerated metal-free catalytic system has been discovered for the Mukaiyama-aldol reaction.The system involves the use of B(C_(6)F_(5))_(3) as a catalyst,which is water-tolerant and able to activate the carbonyl group through a hydrogen bonding network generated by the catalyst.This activation method allows the reactions to be performed with very low catalyst loading,as low as 0.5 mol%.The scope of substrates is broad and a wide variety of functional groups are well tolerated.Diverse aliphatic aldehydes,aromatic aldehydes,unsaturated aldehydes and aromatic ketones coupled with silyl enol ethers/silyl ketone acetals to generate their correspondingβ-hydroxy carbonyl compounds in moderate to good yields.This discovery represents a significant advancement in the field of organic synthesis,as it provides a new,practical and sustainable solution for carbon-carbon bond formation in water.
基金supported by Ministry of Science and Technology of China (Grant No. 2018YFA0606501)National Natural Science Foundation of China (Grant No. 42075037)+1 种基金Key Laboratory Open Research Program of Xinjiang Science and Technology Department (Grant No. 2022D04009)the National Key Scientific and Technological Infrastructure project “Earth System Numerical Simulation Facility” (EarthLab)。
文摘Both the attribution of historical change and future projections of droughts rely heavily on climate modeling. However,reasonable drought simulations have remained a challenge, and the related performances of the current state-of-the-art Coupled Model Intercomparison Project phase 6(CMIP6) models remain unknown. Here, both the strengths and weaknesses of CMIP6 models in simulating droughts and corresponding hydrothermal conditions in drylands are assessed.While the general patterns of simulated meteorological elements in drylands resemble the observations, the annual precipitation is overestimated by ~33%(with a model spread of 2.3%–77.2%), along with an underestimation of potential evapotranspiration(PET) by ~32%(17.5%–47.2%). The water deficit condition, measured by the difference between precipitation and PET, is 50%(29.1%–71.7%) weaker than observations. The CMIP6 models show weaknesses in capturing the climate mean drought characteristics in drylands, particularly with the occurrence and duration largely underestimated in the hyperarid Afro-Asian areas. Nonetheless, the drought-associated meteorological anomalies, including reduced precipitation, warmer temperatures, higher evaporative demand, and increased water deficit conditions, are reasonably reproduced. The simulated magnitude of precipitation(water deficit) associated with dryland droughts is overestimated by 28%(24%) compared to observations. The observed increasing trends in drought fractional area,occurrence, and corresponding meteorological anomalies during 1980–2014 are reasonably reproduced. Still, the increase in drought characteristics, associated precipitation and water deficit are obviously underestimated after the late 1990s,especially for mild and moderate droughts, indicative of a weaker response of dryland drought changes to global warming in CMIP6 models. Our results suggest that it is imperative to employ bias correction approaches in drought-related studies over drylands by using CMIP6 outputs.
基金supported by The Second Tibetan Plateau Scientific Expedition and Research(STEP)program(Grant No.2019QZKK0102)the National Natural Science Foundation of China(Grant No.41975135)+1 种基金the Natural Science Foundation of Sichuan,China(Grant No.2022NSFSC1092)funded by the China Scholarship Council。
文摘The diurnal temperature range(DTR)serves as a vital indicator reflecting both natural climate variability and anthropogenic climate change.This study investigates the historical and projected multitemporal DTR variations over the Tibetan Plateau.It assesses 23 climate models from phase 6 of the Coupled Model Intercomparison Project(CMIP6)using CN05.1 observational data as validation,evaluating their ability to simulate DTR over the Tibetan Plateau.Then,the evolution of DTR over the Tibetan Plateau under different shared socioeconomic pathway(SSP)scenarios for the near,middle,and long term of future projection are analyzed using 11 selected robustly performing models.Key findings reveal:(1)Among the models examined,BCC-CSM2-MR,EC-Earth3,EC-Earth3-CC,EC-Earth3-Veg,EC-Earth3-Veg-LR,FGOALS-g3,FIO-ESM-2-0,GFDL-ESM4,MPI-ESM1-2-HR,MPI-ESM1-2-LR,and INM-CM5-0 exhibit superior integrated simulation capability for capturing the spatiotemporal variability of DTR over the Tibetan Plateau.(2)Projection indicates a slightly increasing trend in DTR on the Tibetan Plateau in the SSP1-2.6 scenario,and decreasing trends in the SSP2-4.5,SSP3-7.0,and SPP5-8.5 scenarios.In certain areas,such as the southeastern edge of the Tibetan Plateau,western hinterland of the Tibetan Plateau,southern Kunlun,and the Qaidam basins,the changes in DTR are relatively large.(3)Notably,the warming rate of maximum temperature under SSP2-4.5,SSP3-7.0,and SPP5-8.5 is slower compared to that of minimum temperature,and it emerges as the primary contributor to the projected decrease in DTR over the Tibetan Plateau in the future.
基金supported by grants The Natural Science Foundation of Inner Mongolia(2019MS08104)The Natural Science Foundation of Inner Mongolia(2022ZD09)The Central Government Guiding Special Funds for Development of Local Science and Technology(2020ZY0020).
文摘Background:The active components of Horcha-6 were identified using liquid chromatography with tandem mass spectrometry.Also,we investigated the potential mechanisms that explain why Horcha-6 may be effective in treating migraines through the use of network pharmacology and a rat migraine model.Methods:After identifying the active components of Horcha-6,the corresponding genes of the active components’target were obtained from the Universal Protein database,and a“compound-target-disease”network was constructed using Cytoscape 3.9.0 software.For the in vivo experiments,nitroglycerin was injected intraperitoneally into rats to create a migraine model.Pre-treatment with Horcha-6 was administered orally for 14 days,and rats were subjected to migraine-related behavior tests.RNA sequencing was performed to identify the gene expression regulated by Horcha-6 in the trigeminal nerve.Results:A total of 903 chemical components of Horcha-6 have been collected in the liquid chromatography with tandem mass spectrometry.We discovered 55 of the Horcha-6 bio-active components that were evaluated based on their Percent Human Oral Absorption(≥30%)and DL values(≥0.185)on the traditional Chinese medicine systems pharmacology database.The“compound-target-disease”network contained 163 intersection targets with the migraine state.Gene Ontology analysis indicated that these components significantly regulated the immune response,vascular function,oxidative stress,etc.When Kyoto Encyclopedia of Genes and Genomes enrichment analysis was performed,we observed that most of the target genes were significantly enriched in the inflammation and neuro-related signaling pathway,toll-like receptor signaling pathway,neuroactive ligand-receptor interaction,etc.These predictions were further demonstrated via in vivo animal model experiments.The RNA sequencing results showed that 41 genes were down-regulated(P<0.05)and 86 genes were up-regulated(P<0.05)in the Horcha-6 treated group compared with the untreated group.Those genes were mainly involved in neuromodulation,vascular function,and hormone metabolism.Conclusion:The 55 bio-active components in Horcha-6 regulate inflammation,hormone metabolism,and neurotransmitters and have potential as a therapy to treat migraines.
基金funding by Comunidad de Madrid within the framework of the Multiannual Agreement with Universidad Politécnica de Madrid to encourage research by young doctors(PRINCE project).
文摘Future 6G communications are envisioned to enable a large catalogue of pioneering applications.These will range from networked Cyber-Physical Systems to edge computing devices,establishing real-time feedback control loops critical for managing Industry 5.0 deployments,digital agriculture systems,and essential infrastructures.The provision of extensive machine-type communications through 6G will render many of these innovative systems autonomous and unsupervised.While full automation will enhance industrial efficiency significantly,it concurrently introduces new cyber risks and vulnerabilities.In particular,unattended systems are highly susceptible to trust issues:malicious nodes and false information can be easily introduced into control loops.Additionally,Denialof-Service attacks can be executed by inundating the network with valueless noise.Current anomaly detection schemes require the entire transformation of the control software to integrate new steps and can only mitigate anomalies that conform to predefined mathematical models.Solutions based on an exhaustive data collection to detect anomalies are precise but extremely slow.Standard models,with their limited understanding of mobile networks,can achieve precision rates no higher than 75%.Therefore,more general and transversal protection mechanisms are needed to detect malicious behaviors transparently.This paper introduces a probabilistic trust model and control algorithm designed to address this gap.The model determines the probability of any node to be trustworthy.Communication channels are pruned for those nodes whose probability is below a given threshold.The trust control algorithmcomprises three primary phases,which feed themodel with three different probabilities,which are weighted and combined.Initially,anomalous nodes are identified using Gaussian mixture models and clustering technologies.Next,traffic patterns are studied using digital Bessel functions and the functional scalar product.Finally,the information coherence and content are analyzed.The noise content and abnormal information sequences are detected using a Volterra filter and a bank of Finite Impulse Response filters.An experimental validation based on simulation tools and environments was carried out.Results show the proposed solution can successfully detect up to 92%of malicious data injection attacks.
基金Supported by the National Natural Science Foundation of China(NSFC)(No.41976027)。
文摘The subtropical North and South Pacific Meridional Modes(NPMM and SPMM)are well known precursors of El Niño-Southern Oscillation(ENSO).However,relationship between them is not constant.In the early 1980,the relationship experienced an interdecadal transition.Changes in this connection can be attributed mainly to the phase change of the Pacific decadal oscillation(PDO).During the positive phase of PDO,a shallower thermocline in the central Pacific is responsible for the stronger trade wind charging(TWC)mechanism,which leads to a stronger equatorial subsurface temperature evolution.This dynamic process strengthens the connection between NPMM and ENSO.Associated with the negative phase of PDO,a shallower thermocline over southeastern Pacific allows an enhanced wind-evaporation-SST(WES)feedback,strengthening the connection between SPMM and ENSO.Using 35 Coupled Model Intercomparison Project Phase 6(CMIP6)models,we examined the NPMM/SPMM performance and its connection with ENSO in the historical runs.The great majority of CMIP6 models can reproduce the pattern of NPMM and SPMM well,but they reveal discrepant ENSO and NPMM/SPMM relationship.The intermodal uncertainty for the connection of NPMM-ENSO is due to different TWC mechanism.A stronger TWC mechanism will enhance NPMM forcing.For SPMM,few models can simulate a good relationship with ENSO.The intermodel spread in the relationship of SPMM and ENSO owing to SST bias in the southeastern Pacific,as WES feedback is stronger when the southeastern Pacific is warmer.
