As a water layer with significantly reduced dissolved oxygen(DO)in the ocean,the oxygen minimum zone(OMZ)plays a crucial role in regulating marine organism distribution,global material cycles,and climate change.Based ...As a water layer with significantly reduced dissolved oxygen(DO)in the ocean,the oxygen minimum zone(OMZ)plays a crucial role in regulating marine organism distribution,global material cycles,and climate change.Based on a systematic review of recent studies on OMZ,this paper summarizes the DO thresholds,structural characteristics,distribution patterns,formation and maintenance mechanisms,and driving factors of OMZ in the ocean in the context of global change.The DO thresholds of OMZ typically range from 20 to 100μmol L^(-1).Specifically,the threshold is mostly 20μmol L^(-1) in regions with intense OMZ,such as the Eastern Pacific and Northern Indian Oceans,while it is mostly 100μmol L^(-1) in regions with mild OMZ,including the Western Pacific and Atlantic.In terms of structure,the OMZ is mainly composed of three parts:the upper oxycline,the lower oxycline,and the OMZ core.Significant differences exist in the horizontal and vertical distributions of OMZ across different regions.OMZ is mainly concentrated in tropical and subtropical regions,with the widest distribution in the eastern tropical North Pacific.The upper boundary of OMZ is shallower(50-150 m)in significantly affected regions,whereas it is below 200 m in less affected regions.The formation of OMZ is governed by the continuous consumption of DO in the ocean interior,and the water exchange restriction caused by seawater stratification,whereas the maintenance of the hypoxic state of OMZ relies on two positive feedbacks:increased microbial oxygen consumption due to reduced animal feeding,and increased oxygen consumption by anaerobic metabolic products.In the context of global change,rising temperature is the main driver of OMZ expansion,reducing O_(2) solubility,increasing respiration and decomposition rates,and enhancing seawater stratification.Additionally,the structure and evolution of OMZ is also profoundly affected by ocean circulation such as thermohaline circulation,wind-driven circulation,and upwelling,as well as changes in wind stress,mesoscale eddies and freshwater flux.Future research should focus on establishing OMZ gradient thresholds and classification criteria based on the law of deoxygenation,improving the systematic understanding of the temporal and spatial variations of OMZ,and continuously strengthening studies on OMZ in the Western Pacific.展开更多
Mega low Earth orbit(LEO)satellite networks serve as effective complements to terrestrial networks.However,the dual mobility of users and LEO satellites makes inter-satellite handovers more frequent for users.Moreover...Mega low Earth orbit(LEO)satellite networks serve as effective complements to terrestrial networks.However,the dual mobility of users and LEO satellites makes inter-satellite handovers more frequent for users.Moreover,there are both ascending and descending segments in widely deployed walker-delta constellations.Even if the locations of users do not change,when the access satellites of the communicating parties are not in the same ascending or descending segment,the end-to-end latency between them will increase.To address this challenge,the self-decision handover(SDH)strategy and the joint decision handover(JDH)strategy are proposed,and they both incorporate the routing hops as a crucial handover criterion to minimize the end-to-end latency.In addition,the shortest route hop-count algorithm is designed to assist in the handover decision-making process.Simulations demonstrate that the proposed handover strategies outperform the traditional handover strategies in terms of the number of handovers and end-to-end latency.展开更多
In this study,three specific scenarios of a novel accelerator light source mechanism called steady-state microbunching(SSMB)were studied:longitudinal weak focusing,longitudinal strong focusing,and generalized longitud...In this study,three specific scenarios of a novel accelerator light source mechanism called steady-state microbunching(SSMB)were studied:longitudinal weak focusing,longitudinal strong focusing,and generalized longitudinal strong focusing(GLSF).At present,GLSF is the most promising method for realizing high-power short-wavelength coherent radiation with mild requirements on modulation laser power.Its essence is to exploit the ultrasmall natural vertical emittance of an electron beam in a planar storage ring for efficient microbunching formation,like a partial transverse-longitudinal emittance exchange in the optical laser wavelength range.Based on an in-depth investigation of related beam physics,a solution for a GLSF SSMB storage ring that can deliver 1 kW average-power EUV light is presented.The work in this paper,such as the generalized Courant–Snyder formalism,analysis of theoretical minimum emittances,transverse-longitudinal coupling dynamics,and derivation of the bunching factor and modulation strengths for laser-induced microbunching schemes,is expected to be useful not only for the development of SSMB but also for future accelerator light sources in general that demand increasingly precise electron beam phase space manipulations.展开更多
Climate change is altering river regimes in mountainous regions,affecting water availability and the functioning of aquatic ecosystems.In the Andes Mountains,characterizing the natural flow regime is essential for est...Climate change is altering river regimes in mountainous regions,affecting water availability and the functioning of aquatic ecosystems.In the Andes Mountains,characterizing the natural flow regime is essential for establishing operational conditions that balance multiple water uses(irrigation,supply,hydropower)with the conservation of high-elevation ecosystems in the context of increasing hydroclimatic variability.This study analyzes extreme hydrological conditions in nivoglacial rivers of the upper Mendoza River Basin(Argentina),using indicators of magnitude,frequency,duration,and timing of high(HP)and low(LP)pulses.Daily flow records from the Cuevas,Vacas,Tupungato,and Mendoza Rivers were used to define eight ecologically relevant extreme hydrological parameters over the period 1956–2023.The results reveal a reduction in the magnitude of extreme flows since 2010(−30%to–55%)and significant delays in their timing,with maximum and minimum flow shifting by 15–20 days later in recent decades.The duration of LP events increased by 120%–240%in the Cuevas,Tupungato,and Mendoza Rivers,while in the Tupungato River,HP events tended to occur less frequently but with longer durations.These changes are associated with a 0.1℃decade^(−1)rise in mean temperature and a∼25%decrease in precipitation since 2009.Such trends have major implications for water resource management and the resilience of high-Andean ecosystems under climate warming.展开更多
Minimum quantity lubrication(MQL),as a new sustainable and eco-friendly alternative cooling/lubrication technology that addresses the limitations of dry and wet machining,utilizes a small amount of lubricant or coolan...Minimum quantity lubrication(MQL),as a new sustainable and eco-friendly alternative cooling/lubrication technology that addresses the limitations of dry and wet machining,utilizes a small amount of lubricant or coolant to reduce friction,tool wear,and heat during cutting processes.MQL technique has witnessed significant developments in recent years,such as combining MQL with other sustainable techniques to achieve optimum results,using biodegradable lubricants,and innovations in nozzle designs and delivery methods.This review presents an in-depth analysis of machining characteristics(e.g.,cutting forces,temperature,tool wear,chip morphology and surface integrity,etc.)and sustainability characteristics(e.g.,energy consumption,carbon emissions,processing time,machining cost,etc.)of conventional MQL and hybrid MQL techniques like cryogenic MQL,Ranque-Hilsch vortex tube MQL,nanofluids MQL,hybrid nanofluid MQL and ultrasonic vibration assisted MQL in machining of aeronautical materials.Subsequently,the latest research and developments are analyzed and summarized in the field of MQL,and provide a detailed comparison between each technique,considering advantages,challenges,and limitations in practical implementation.In addition,this review serves as a valuable source for researchers and engineers to optimize machining processes while minimizing environmental impact and operational costs.Ultimately,the potential future aspects of MQL for research and industrial execution are discussed.展开更多
In the practice of healthcare,patient-reported outcomes(PROs)and PRO measures(PROMs)are used as an attempt to observe the changes in complex clinical situations.They guide us in making decisions based on the evidence ...In the practice of healthcare,patient-reported outcomes(PROs)and PRO measures(PROMs)are used as an attempt to observe the changes in complex clinical situations.They guide us in making decisions based on the evidence regarding patient care by recording the change in outcomes for a particular treatment to a given condition and finally to understand whether a patient will benefit from a particular treatment and to quantify the treatment effect.For any PROM to be usable in health care,we need it to be reliable,encapsulating the points of interest with the potential to detect any real change.Using structured outcome measures routinely in clinical practice helps the physician to understand the functional limitation of a patient that would otherwise not be clear in an office interview,and this allows the physician and patient to have a meaningful conver-sation as well as a customized plan for each patient.Having mentioned the rationale and the benefits of PROMs,understanding the quantification process is crucial before embarking on management decisions.A better interpretation of change needs to identify the treatment effect based on clinical relevance for a given condition.There are a multiple set of measurement indices to serve this effect and most of them are used interchangeably without clear demarcation on their differences.This article details the various quantification metrics used to evaluate the treatment effect using PROMs,their limitations and the scope of usage and implementation in clinical practice.展开更多
In shale reservoirs,fluids are often confined within nanopores,leading to apparent effects on the properties and phase behavior of the fluid.However,previous studies have primarily focused on the effect of capillary p...In shale reservoirs,fluids are often confined within nanopores,leading to apparent effects on the properties and phase behavior of the fluid.However,previous studies have primarily focused on the effect of capillary pressure or adsorption on well performance,and only a very limited number of studies have researched the complex and coupled impact of confinement on capillarity,adsorption,and interactions between fluid molecules and pore walls.Therefore,in this study,an effective method is developed for evaluating the coupled effects of nanopore confinement on CO_(2) injection performance.First,a comprehensive thermodynamic model that incorporates adsorption,capillary pressure,and molecule-wall interaction in nanopores by modifying the Peng-Robinson equation of state(PR-EOS)is proposed.Subsequently,the calculated critical properties of different components are validated against experimental measured data,illustrating that the developed model can accurately predict the properties of the components of CO_(2)-hydrocarbon systems.Numerical simulations of field-scale case studies were then performed and calibrated using a modified phase equilibrium model.Typical fluid properties were inputted to investigate the effect of nanopore confinement on the CO_(2) injection performance.The results of this study show that the ultimate recovery factor increases by approximately 4.61%at a pore size of 10 nm,indicating that nanopore confinement is advantageous to well performance.Light hydrocarbons undergo more intense mass transfer than heavy hydrocarbons.Furthermore,as the pore radius decreased from 100 nm to 10 nm,the CO_(2) storage coefficient increased by 2.8%.The findings of this study deepen the collective understanding of the effect of nanopore confinement on CO_(2) displacement and storage,which has significant field-scale applications.展开更多
Fracture(fault)reactivation can lead to dynamic geological hazards including earthquakes,rock collapses,landslides,and rock bursts.True triaxial compression tests were conducted to analyze the fracture reactivation pr...Fracture(fault)reactivation can lead to dynamic geological hazards including earthquakes,rock collapses,landslides,and rock bursts.True triaxial compression tests were conducted to analyze the fracture reactivation process under two different orientations of σ_(2),i.e.σ_(2) parallel to the fracture plane(Scheme 2)and σ_(2) cutting through the fracture plane(Scheme 3),under varying σ_(3) from 10 MPa to 40 MPa.The peak or fracture reactivation strength,deformation,failure mode,and post-peak mechanical behavior of intact(Scheme 1)and pre-fractured(Schemes 2 and 3)specimens were also compared.Results show that for intact specimens,the stress remains nearly constant in the residual sliding stage with no stick-slip,and the newly formed fracture surface only propagates along the σ_(2) direction when σ_(3) ranges from 10 MPa to 30 MPa,while it extends along both σ_(2) and σ_(3) directions when σ_(3) increases to 40 MPa;for the pre-fractured specimens,the fractures are usually reactivated under all the σ_(3) levels in Scheme 2,but fracture reactivation only occurs when σ_(3) is greater than 25 MPa in Scheme 3,below which new faulting traversing the original macro fracture occurs.In all the test schemes,both ε_(2) and ε_(3) experience an accumulative process of elongation,after which an abrupt change occurs at the point of the final failure;the degree of this change is dependent on the orientation of the new faulting or the slip direction of the original fracture,and it is generally more than 10 times larger in the slip direction of the original fracture than in the non-slip direction.Besides,the differential stress(peak stress)required for reactivation and the post-peak stress drop increase with increasing σ_(3).Post-peak stress drop and residual strength in Scheme 3 are generally greater than those in Scheme 2 at the same σ_(3) value.Our study clearly shows that intermediate principal stress orientation not only affects the fracture reactivation strength but also influences the slip deformation and failure modes.These new findings facilitate the mitigation of dynamic geological hazards associated with fracture and fault slip.展开更多
Arctic sea-ice extent reaches its minimum each year in September. On 11 September 2023 the minimum was 4.969 million square kilometers(mill.km^(2)). This was not a record low, which occurred in 2012, when the minimum ...Arctic sea-ice extent reaches its minimum each year in September. On 11 September 2023 the minimum was 4.969 million square kilometers(mill.km^(2)). This was not a record low, which occurred in 2012, when the minimum was 4.175 mill.km^(2), 0.794 mill.km^(2) less than the minimum in 2023. However, the ice extent had decreased by 0.432 mill.km^(2) compared with 2022. Nevertheless, the summer melting in 2023 was remarkably less than expected when considering the strong heat waves in the atmosphere and ocean, with record temperatures set around the world. In general, there is a high correlation between the long-term decrease in sea-ice extent and the increasing CO_(2) in the atmosphere, where the increase of CO_(2) in recent decades explains about 80% of the decrease in sea ice in September, while the remainder is caused by natural variability.展开更多
Solar cycles are fundamental to astrophysics,space exploration,technological infrastructure,and Earth's climate.A better understanding of these cycles and their history can aid in risk mitigation on Earth,while al...Solar cycles are fundamental to astrophysics,space exploration,technological infrastructure,and Earth's climate.A better understanding of these cycles and their history can aid in risk mitigation on Earth,while also deepening our knowledge of stellar physics and solar system dynamics.Determining the solar cycles between 1600 and 1700-especially the post-1645 Maunder Minimum,characterized by significantly reduced solar activity-poses challenges to existing solar activity proxies.This study utilizes a new red equatorial auroral catalog from ancient Korean texts to establish solar cycle patterns from 1623 to 1700.Remarkably,a further reevaluation of the solar cycles between 1610 and 1755 identified a total of 13 cycles,diverging from the widely accepted record of 12 cycles during that time.This research enhances our understanding of historical solar activity,and underscores the importance of integrating diverse historical sources into modern analyses.展开更多
Currently,the International Maritime Organization(IMO)has approved and implemented the assessment requirement for Minimum Propulsion Power(MPP)of ships in adverse sea conditions.The assessment method and relevant infl...Currently,the International Maritime Organization(IMO)has approved and implemented the assessment requirement for Minimum Propulsion Power(MPP)of ships in adverse sea conditions.The assessment method and relevant influence factors will have a vital impact on ship's design and operation.On the other hand,MPP is essentially a criterion for manoeuvring safety at actual seas.However,the practical assessment methods adopted in IMO guidelines do not directly and accurately account for ship's coursekeeping ability in severe seas.A time-domain comprehensive method with supplementary course-keeping ability criteria has been proposed in the authors'preliminary research.Based on an updated mathematical model and criteria,this paper presents more detailed elaborations,results and discussions on the time-domain method,including the comparative analyses with a power line method and two steady-state equilibrium methods based on IMO guidelines and draft.Discussions on the influences of key factors,involving criterion conditions and calculation parameters,are also presented.The results indicate that different methods exhibit varying advantages and complexity in MPP assessment,thus constituting a multi-level assessment framework for MPP.In particular,the time-domain comprehensive assessment has a higher accuracy with more realistic description of manoeuvre behaviors,capable of offering a solution for the ships that cannot meet other assessments,or for the assessment requiring additional course-keeping ability.Furthermore,an expanded range of wave direction sets a stricter but potentially necessary requirement,while using the self-propulsion factors at low speeds can eliminate the unnecessary conservation of assessment result caused by those at design speed.展开更多
For a graph G,a vertex is said to be pendant if its neighborhood contains exactly one vertex.In this paper,we determine the extremal graphs among all n-vertex graphs with the minimum spectral radius andβpendant verti...For a graph G,a vertex is said to be pendant if its neighborhood contains exactly one vertex.In this paper,we determine the extremal graphs among all n-vertex graphs with the minimum spectral radius andβpendant vertices,whereβe{1,2,3,4,n-3,n-2,n-1}.展开更多
Cranes used at sea have some shortcomings in terms of flexibility,efficiency,and safety.Therefore,a floating multi-robot coordinated towing system is planned to fulfill the offshore towing requirements.It is difficult...Cranes used at sea have some shortcomings in terms of flexibility,efficiency,and safety.Therefore,a floating multi-robot coordinated towing system is planned to fulfill the offshore towing requirements.It is difficult to study the stability of a floating multi-robot coordinated towing system by ancient strategies.First,the minimum tension of the rope and the minimum singular value of the stiffness matrix were separately used to analyze the load stability.The advantages and disadvantages of the two methods were discussed.Then,the two stability analysis methods were normalized and weighted to obtain the method based on minimum tension and minimum singular to comprehensively analyze the stability of the load.Finally,the effect of different weighting coefficients on the load stability was analyzed,which led to a reasonable weighting coefficient to evaluate the load stability by comparing with a single analysis method.The research results provide a basis for the motion planning and coordinated control of the towing system.展开更多
As the manufacturing industry shifts toward environmentally sustainable practices,grinding—a high-precision pro-cessing method—is commonly used to ensure final workpiece dimensions and surface quality.The greening o...As the manufacturing industry shifts toward environmentally sustainable practices,grinding—a high-precision pro-cessing method—is commonly used to ensure final workpiece dimensions and surface quality.The greening of grind-ing processes has emerged as an important challenge for both academia and industry.Numerous studies proposing different methods for sustainable grinding have increased rapidly;however,the technical mechanisms and develop-ment trends remain unclear.This paper applies bibliometric methods to analyze relevant articles published on WOS from 2008 to 2023.Results show that China has the highest number of publications(45.38%),with research institu-tions primarily located in China,India,and Brazil.Among publishing journals,70%are classified as Q2 or above.Addi-tionally,popular authors and influential articles in this field are identified.Keyword frequency and hotspot literature analysis reveal that research focuses primarily on minimal quantity lubrication(MQL)grinding,especially using biolubricants and nanoparticles to improve grinding performance.This article reviews the mechanisms and effects of biolubricants and nanoparticles in MQL.It further examines how multi-energy field applications enhance MQL by influencing droplet atomization,wettability,and machining performance.A low-temperature field improves the heat exchange capacity of MQL droplets,while an electrostatic field enhances droplet contact angles and disper-sion.Ultrasonic energy enhances the atomization of biolubricants,and magnetic fields facilitate nanoparticle penetra-tion into the grinding zone,reducing grinding forces.Additionally,innovations in grinding wheel structures and solid lubrication grinding can reduce grinding temperatures and forces.This paper presents a comprehensive review of eco-friendly grinding development hotspots,providing technical support and theoretical guidance for academia and industry.展开更多
The use of Minimum Quantity Lubrication(MQL)with bio-lubricants has been extensively studied in aerospace sustainable manufacturing.Enhanced MQL technologies have been proposed to reduce tool wear and improve workpiec...The use of Minimum Quantity Lubrication(MQL)with bio-lubricants has been extensively studied in aerospace sustainable manufacturing.Enhanced MQL technologies have been proposed to reduce tool wear and improve workpiece surface integrity by increasing lubricant activity.However,the relationship between enhancement behavior,physicochemical properties of biolubricants,and processability remains unclear,presenting challenges for MQL technologies,particularly with difficult-to-machine materials.To address this gap,this paper provides an in-depth mechanism analysis and a comprehensive quantitative evaluation of the machinability of enhanced MQL technologies,considering chemistry,molecular dynamics,fluid dynamics,tribology,and heat transfer.Firstly,the cooling and lubrication enhancement mechanisms of nano-lubricants were systematically summarized.focusing on molecular structure.physical properties,and preparation processes.Secondly,the atomization enhancement mechanism of Electrostatic Minimum Quantity Lubrication(EMQL)was analyzed.revealing a 49%reduction in PM2.5 concentration during the atomization process compared to conventional MQL.Thirdly,the transport and infiltration enhancement mechanisms of bio-lubricants in cutting and grinding zones were summarized,incorporating electromagnetic fields and ultrasound-assisted processes.Finally,for cutting and grinding applications involving difficult-to-machine materials in aerospace,the optimized machinability of enhanced MQL technologies was concluded,showing a 50.1%increase in lubricant heat transfer coefficient and a 31.6%decrease in grinding temperature compared to standard MQL.This paper aims to help scientists understand the effective mechanisms,formulate process specifications,and identify future development trends in this technology.展开更多
Conventional adaptive filtering algorithms often exhibit performance degradation when processing multipath interference in raw echoes of spaceborne synthetic aperture radar(SAR)systems due to anomalous outliers,manife...Conventional adaptive filtering algorithms often exhibit performance degradation when processing multipath interference in raw echoes of spaceborne synthetic aperture radar(SAR)systems due to anomalous outliers,manifesting as insufficient convergence and low estimation accuracy.To address this issue,this study proposes a novel robust adaptive filtering algorithm,namely the M-estimation-based minimum error entropy with affine projection(APMMEE)algorithm.This algorithm inherits the joint multi-data-block update mechanism of the affine projection algorithm,enabling rapid adaptation to the dynamic characteristics of raw echoes and achieving fast convergence.Meanwhile,it incorporates the M-estimation-based minimum error entropy(MMEE)criterion,which weights error samples in raw echoes through M-estimation functions,effectively suppressing outlier interference during the algorithm update.Both the system identification simulations and practical multipath interference suppression experiments using raw echoes demonstrate that the proposed APMMEE algorithm exhibits superior filtering performance.展开更多
Dengue is a mosquito-borne disease that is rampant worldwide,with up to 70%of cases reported to be asymptomatic during epidemics.In this paper,a reaction-diffusion dengue model with asymptomatic carrier transmission i...Dengue is a mosquito-borne disease that is rampant worldwide,with up to 70%of cases reported to be asymptomatic during epidemics.In this paper,a reaction-diffusion dengue model with asymptomatic carrier transmission is investigated.We aim to study the existence,nonexistence and minimum wave speed of traveling wave solutions to the model.The results show that the existence and nonexistence of traveling wave solutions are fully determined by the threshold values,which are,the basic reproduction number R0 and critical wave speed c^(*)>0.Specifically,when R0>1 and the wave speed c≥c^(*),the existence of the traveling wave solution is obtained by using Schauder's fixed point theorem and Lyapunov functional.It is proven that the model has no nontrivial traveling wave solutions for R0≤1 or R0>1 and 0<c<c^(*)by employing comparison principle and limit theory.As a consequence,we conclude that the critical wave speed c^(*)is the minimum wave speed of the model.Finally,numerical simulations are carried out to illustrate the effects of several important parameters on the minimum wave speed.展开更多
The interactions between fire,ecosystems,and climate are complex.Tropical ecosystems have dominated global active fires nowadays,yet its causes,mechanisms,and consequences remain relatively poorly understood.To in-ves...The interactions between fire,ecosystems,and climate are complex.Tropical ecosystems have dominated global active fires nowadays,yet its causes,mechanisms,and consequences remain relatively poorly understood.To in-vestigate temporal response of remotely-sensed active fires to intra-annual climate change,several 1-km datasets,including the Moderate-resolution Imaging Spectroradiometer Collection 6(MODIS C6)active fires and the Cli-matologies at High Resolution for the Earth’s Land Surface Areas(CHELSA)climate variables,were gathered to examine the climatic characteristics of active fire incidences,fire-climate correlations,and the average monthly response of active fire occurrences to climate change using the Geographic Information System(GIS)Fishnet tool,Theil-Sen Median slope estimation,Mann-Kendall significance test,and Pearson’s correlation.We concluded that climate variables’trends of nearly two-decade active fires displayed varied degrees of increment in precipitation(Pre),temperature(Tas),and surface downwelling shortwave radiation(Rsds)and inconsistent decrement in near-surface relative humidity(Hurs)and near-surface wind speed(sfcWind).MODIS multi-year(2003-2018)active fires were moderately to strongly correlated negatively with Pre and Hurs at 10 km grid-resolution but positively with sfcWind and Rsds,showing marked geographical variations in correlation direction and strength.The most significant finding is the newly observed inverse relationship between active fires and precipitation on both sides of the equator.High occurrence areas of active fires regularly appear back and forth along with latitudinal changes(at one-degree intervals)in monthly minimum precipitation between the tropical Northern and Southern Hemispheres.The present study contributes to exploring the underlying mechanism of fire-climate interactions against the backdrop of climate warming.展开更多
This paper proposes an extension of the Modified-Plant ADRC(MP-ADRC)strategy to broaden its application to minimum phase dynamical systems.The main features of the MP-ADRC method are the inclusion of a constant gain i...This paper proposes an extension of the Modified-Plant ADRC(MP-ADRC)strategy to broaden its application to minimum phase dynamical systems.The main features of the MP-ADRC method are the inclusion of a constant gain in series with the plant output error and a linear filter in parallel with the overall error system.These structural changes do not influence the input/output dynamics of the original plant,but are intentionally introduced to modify the dynamics to be estimated by the extended state observer(ESO)and,thus,promote an increase in the robustness of the method.Some advantages can also be attributed to the proposed methodology,such as(i)the design procedures of both the controller and the ESO only require knowledge of the sign(±)of the plant input channel coefficient(or control gain);(ii)the plant control input is generated directly by a single ESO state variable.Despite the advantages and the characteristics of MP-ADRC mentioned earlier,closed-loop stability cannot be guaranteed when it is applied to dynamical systems that have finite zeros.To overcome this difficulty,this work introduces an extension in the MP-ADRC method.It basically consists of rewriting the minimum phase plant dynamics according to its relative order,and then follows with the design of the ESO by conveniently increasing the number of ESO state variables.The simulation results are also presented to illustrate the application of the proposed method.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42206135,42476204)the Shandong Provincial Natural Science Foundation(Grant Nos.ZR2025MS664,ZR2025MS611,ZR2022QD019).
文摘As a water layer with significantly reduced dissolved oxygen(DO)in the ocean,the oxygen minimum zone(OMZ)plays a crucial role in regulating marine organism distribution,global material cycles,and climate change.Based on a systematic review of recent studies on OMZ,this paper summarizes the DO thresholds,structural characteristics,distribution patterns,formation and maintenance mechanisms,and driving factors of OMZ in the ocean in the context of global change.The DO thresholds of OMZ typically range from 20 to 100μmol L^(-1).Specifically,the threshold is mostly 20μmol L^(-1) in regions with intense OMZ,such as the Eastern Pacific and Northern Indian Oceans,while it is mostly 100μmol L^(-1) in regions with mild OMZ,including the Western Pacific and Atlantic.In terms of structure,the OMZ is mainly composed of three parts:the upper oxycline,the lower oxycline,and the OMZ core.Significant differences exist in the horizontal and vertical distributions of OMZ across different regions.OMZ is mainly concentrated in tropical and subtropical regions,with the widest distribution in the eastern tropical North Pacific.The upper boundary of OMZ is shallower(50-150 m)in significantly affected regions,whereas it is below 200 m in less affected regions.The formation of OMZ is governed by the continuous consumption of DO in the ocean interior,and the water exchange restriction caused by seawater stratification,whereas the maintenance of the hypoxic state of OMZ relies on two positive feedbacks:increased microbial oxygen consumption due to reduced animal feeding,and increased oxygen consumption by anaerobic metabolic products.In the context of global change,rising temperature is the main driver of OMZ expansion,reducing O_(2) solubility,increasing respiration and decomposition rates,and enhancing seawater stratification.Additionally,the structure and evolution of OMZ is also profoundly affected by ocean circulation such as thermohaline circulation,wind-driven circulation,and upwelling,as well as changes in wind stress,mesoscale eddies and freshwater flux.Future research should focus on establishing OMZ gradient thresholds and classification criteria based on the law of deoxygenation,improving the systematic understanding of the temporal and spatial variations of OMZ,and continuously strengthening studies on OMZ in the Western Pacific.
基金supported by the State Key Laboratory of Micro-Spacecraft Rapid Design and Intelligent Cluster(MS01240103)the National Natural Science Foundation of China(62071146,62431009)+2 种基金the National 2011 Collaborative Innovation Center of Wireless Communication Technologies(2242022k60006)the Research Project Fund of Songjiang Laboratory(SL20230104)Heilongjiang Province Postdoctoral General Foundation(LBH-Z22133)。
文摘Mega low Earth orbit(LEO)satellite networks serve as effective complements to terrestrial networks.However,the dual mobility of users and LEO satellites makes inter-satellite handovers more frequent for users.Moreover,there are both ascending and descending segments in widely deployed walker-delta constellations.Even if the locations of users do not change,when the access satellites of the communicating parties are not in the same ascending or descending segment,the end-to-end latency between them will increase.To address this challenge,the self-decision handover(SDH)strategy and the joint decision handover(JDH)strategy are proposed,and they both incorporate the routing hops as a crucial handover criterion to minimize the end-to-end latency.In addition,the shortest route hop-count algorithm is designed to assist in the handover decision-making process.Simulations demonstrate that the proposed handover strategies outperform the traditional handover strategies in terms of the number of handovers and end-to-end latency.
基金supported by the National Key Research and Development Program of China(No.2022YFA1603401)National Natural Science Foundation of China(Nos.12035010 and 12342501)+1 种基金Beijing Outstanding Young Scientist Program(No.JWZQ20240101006)the Tsinghua University Dushi Program.
文摘In this study,three specific scenarios of a novel accelerator light source mechanism called steady-state microbunching(SSMB)were studied:longitudinal weak focusing,longitudinal strong focusing,and generalized longitudinal strong focusing(GLSF).At present,GLSF is the most promising method for realizing high-power short-wavelength coherent radiation with mild requirements on modulation laser power.Its essence is to exploit the ultrasmall natural vertical emittance of an electron beam in a planar storage ring for efficient microbunching formation,like a partial transverse-longitudinal emittance exchange in the optical laser wavelength range.Based on an in-depth investigation of related beam physics,a solution for a GLSF SSMB storage ring that can deliver 1 kW average-power EUV light is presented.The work in this paper,such as the generalized Courant–Snyder formalism,analysis of theoretical minimum emittances,transverse-longitudinal coupling dynamics,and derivation of the bunching factor and modulation strengths for laser-induced microbunching schemes,is expected to be useful not only for the development of SSMB but also for future accelerator light sources in general that demand increasingly precise electron beam phase space manipulations.
基金National Scientific and Technical Research Council of Argentina(CONICET),Grant/Award Number:PIBAA2022-202328720210100485CO。
文摘Climate change is altering river regimes in mountainous regions,affecting water availability and the functioning of aquatic ecosystems.In the Andes Mountains,characterizing the natural flow regime is essential for establishing operational conditions that balance multiple water uses(irrigation,supply,hydropower)with the conservation of high-elevation ecosystems in the context of increasing hydroclimatic variability.This study analyzes extreme hydrological conditions in nivoglacial rivers of the upper Mendoza River Basin(Argentina),using indicators of magnitude,frequency,duration,and timing of high(HP)and low(LP)pulses.Daily flow records from the Cuevas,Vacas,Tupungato,and Mendoza Rivers were used to define eight ecologically relevant extreme hydrological parameters over the period 1956–2023.The results reveal a reduction in the magnitude of extreme flows since 2010(−30%to–55%)and significant delays in their timing,with maximum and minimum flow shifting by 15–20 days later in recent decades.The duration of LP events increased by 120%–240%in the Cuevas,Tupungato,and Mendoza Rivers,while in the Tupungato River,HP events tended to occur less frequently but with longer durations.These changes are associated with a 0.1℃decade^(−1)rise in mean temperature and a∼25%decrease in precipitation since 2009.Such trends have major implications for water resource management and the resilience of high-Andean ecosystems under climate warming.
基金financially supported by the National Natural Science Foundation of China(Nos.92160301,92060203,52175415,and 52205475)the Science Center for Gas Turbine Project(Nos.P2022-AB-IV-002-001 and P2023-B-IV-003-001)+2 种基金the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Superior Postdoctoral Project of Jiangsu Province(No.2022ZB215)the National Key Laboratory of Science and Technology on Helicopter Transmission in NUAA(No.HTL-A-22G12).
文摘Minimum quantity lubrication(MQL),as a new sustainable and eco-friendly alternative cooling/lubrication technology that addresses the limitations of dry and wet machining,utilizes a small amount of lubricant or coolant to reduce friction,tool wear,and heat during cutting processes.MQL technique has witnessed significant developments in recent years,such as combining MQL with other sustainable techniques to achieve optimum results,using biodegradable lubricants,and innovations in nozzle designs and delivery methods.This review presents an in-depth analysis of machining characteristics(e.g.,cutting forces,temperature,tool wear,chip morphology and surface integrity,etc.)and sustainability characteristics(e.g.,energy consumption,carbon emissions,processing time,machining cost,etc.)of conventional MQL and hybrid MQL techniques like cryogenic MQL,Ranque-Hilsch vortex tube MQL,nanofluids MQL,hybrid nanofluid MQL and ultrasonic vibration assisted MQL in machining of aeronautical materials.Subsequently,the latest research and developments are analyzed and summarized in the field of MQL,and provide a detailed comparison between each technique,considering advantages,challenges,and limitations in practical implementation.In addition,this review serves as a valuable source for researchers and engineers to optimize machining processes while minimizing environmental impact and operational costs.Ultimately,the potential future aspects of MQL for research and industrial execution are discussed.
文摘In the practice of healthcare,patient-reported outcomes(PROs)and PRO measures(PROMs)are used as an attempt to observe the changes in complex clinical situations.They guide us in making decisions based on the evidence regarding patient care by recording the change in outcomes for a particular treatment to a given condition and finally to understand whether a patient will benefit from a particular treatment and to quantify the treatment effect.For any PROM to be usable in health care,we need it to be reliable,encapsulating the points of interest with the potential to detect any real change.Using structured outcome measures routinely in clinical practice helps the physician to understand the functional limitation of a patient that would otherwise not be clear in an office interview,and this allows the physician and patient to have a meaningful conver-sation as well as a customized plan for each patient.Having mentioned the rationale and the benefits of PROMs,understanding the quantification process is crucial before embarking on management decisions.A better interpretation of change needs to identify the treatment effect based on clinical relevance for a given condition.There are a multiple set of measurement indices to serve this effect and most of them are used interchangeably without clear demarcation on their differences.This article details the various quantification metrics used to evaluate the treatment effect using PROMs,their limitations and the scope of usage and implementation in clinical practice.
基金supported by National Natural Science Foundation of China(Nos.52474052 and 52074248)Young Elite Scientists Sponsorship Program by Beijing Association for Science and Technology,China(No.BYESS2023414)Scientific Research Innovation Capability Support Project for Young Faculty,China(No.ZYGXQNJSKYCXNLZCXM-E14).
文摘In shale reservoirs,fluids are often confined within nanopores,leading to apparent effects on the properties and phase behavior of the fluid.However,previous studies have primarily focused on the effect of capillary pressure or adsorption on well performance,and only a very limited number of studies have researched the complex and coupled impact of confinement on capillarity,adsorption,and interactions between fluid molecules and pore walls.Therefore,in this study,an effective method is developed for evaluating the coupled effects of nanopore confinement on CO_(2) injection performance.First,a comprehensive thermodynamic model that incorporates adsorption,capillary pressure,and molecule-wall interaction in nanopores by modifying the Peng-Robinson equation of state(PR-EOS)is proposed.Subsequently,the calculated critical properties of different components are validated against experimental measured data,illustrating that the developed model can accurately predict the properties of the components of CO_(2)-hydrocarbon systems.Numerical simulations of field-scale case studies were then performed and calibrated using a modified phase equilibrium model.Typical fluid properties were inputted to investigate the effect of nanopore confinement on the CO_(2) injection performance.The results of this study show that the ultimate recovery factor increases by approximately 4.61%at a pore size of 10 nm,indicating that nanopore confinement is advantageous to well performance.Light hydrocarbons undergo more intense mass transfer than heavy hydrocarbons.Furthermore,as the pore radius decreased from 100 nm to 10 nm,the CO_(2) storage coefficient increased by 2.8%.The findings of this study deepen the collective understanding of the effect of nanopore confinement on CO_(2) displacement and storage,which has significant field-scale applications.
基金funding support from the National Nature Science Foundation of China(Grant No.42272334)the National Key Research and Development Program of China(Grant No.2022YFE0137200)the Taishan Scholars Program(Grant No.2019RKB01083).
文摘Fracture(fault)reactivation can lead to dynamic geological hazards including earthquakes,rock collapses,landslides,and rock bursts.True triaxial compression tests were conducted to analyze the fracture reactivation process under two different orientations of σ_(2),i.e.σ_(2) parallel to the fracture plane(Scheme 2)and σ_(2) cutting through the fracture plane(Scheme 3),under varying σ_(3) from 10 MPa to 40 MPa.The peak or fracture reactivation strength,deformation,failure mode,and post-peak mechanical behavior of intact(Scheme 1)and pre-fractured(Schemes 2 and 3)specimens were also compared.Results show that for intact specimens,the stress remains nearly constant in the residual sliding stage with no stick-slip,and the newly formed fracture surface only propagates along the σ_(2) direction when σ_(3) ranges from 10 MPa to 30 MPa,while it extends along both σ_(2) and σ_(3) directions when σ_(3) increases to 40 MPa;for the pre-fractured specimens,the fractures are usually reactivated under all the σ_(3) levels in Scheme 2,but fracture reactivation only occurs when σ_(3) is greater than 25 MPa in Scheme 3,below which new faulting traversing the original macro fracture occurs.In all the test schemes,both ε_(2) and ε_(3) experience an accumulative process of elongation,after which an abrupt change occurs at the point of the final failure;the degree of this change is dependent on the orientation of the new faulting or the slip direction of the original fracture,and it is generally more than 10 times larger in the slip direction of the original fracture than in the non-slip direction.Besides,the differential stress(peak stress)required for reactivation and the post-peak stress drop increase with increasing σ_(3).Post-peak stress drop and residual strength in Scheme 3 are generally greater than those in Scheme 2 at the same σ_(3) value.Our study clearly shows that intermediate principal stress orientation not only affects the fracture reactivation strength but also influences the slip deformation and failure modes.These new findings facilitate the mitigation of dynamic geological hazards associated with fracture and fault slip.
文摘Arctic sea-ice extent reaches its minimum each year in September. On 11 September 2023 the minimum was 4.969 million square kilometers(mill.km^(2)). This was not a record low, which occurred in 2012, when the minimum was 4.175 mill.km^(2), 0.794 mill.km^(2) less than the minimum in 2023. However, the ice extent had decreased by 0.432 mill.km^(2) compared with 2022. Nevertheless, the summer melting in 2023 was remarkably less than expected when considering the strong heat waves in the atmosphere and ocean, with record temperatures set around the world. In general, there is a high correlation between the long-term decrease in sea-ice extent and the increasing CO_(2) in the atmosphere, where the increase of CO_(2) in recent decades explains about 80% of the decrease in sea ice in September, while the remainder is caused by natural variability.
基金supported by the National Natural Science Foundation of China (42388101)the CAS Youth Interdisciplinary Team (JCTD-2021-05)funded by the Youth Innovation Promotion Association, Chinese Academy of Sciences.
文摘Solar cycles are fundamental to astrophysics,space exploration,technological infrastructure,and Earth's climate.A better understanding of these cycles and their history can aid in risk mitigation on Earth,while also deepening our knowledge of stellar physics and solar system dynamics.Determining the solar cycles between 1600 and 1700-especially the post-1645 Maunder Minimum,characterized by significantly reduced solar activity-poses challenges to existing solar activity proxies.This study utilizes a new red equatorial auroral catalog from ancient Korean texts to establish solar cycle patterns from 1623 to 1700.Remarkably,a further reevaluation of the solar cycles between 1610 and 1755 identified a total of 13 cycles,diverging from the widely accepted record of 12 cycles during that time.This research enhances our understanding of historical solar activity,and underscores the importance of integrating diverse historical sources into modern analyses.
文摘Currently,the International Maritime Organization(IMO)has approved and implemented the assessment requirement for Minimum Propulsion Power(MPP)of ships in adverse sea conditions.The assessment method and relevant influence factors will have a vital impact on ship's design and operation.On the other hand,MPP is essentially a criterion for manoeuvring safety at actual seas.However,the practical assessment methods adopted in IMO guidelines do not directly and accurately account for ship's coursekeeping ability in severe seas.A time-domain comprehensive method with supplementary course-keeping ability criteria has been proposed in the authors'preliminary research.Based on an updated mathematical model and criteria,this paper presents more detailed elaborations,results and discussions on the time-domain method,including the comparative analyses with a power line method and two steady-state equilibrium methods based on IMO guidelines and draft.Discussions on the influences of key factors,involving criterion conditions and calculation parameters,are also presented.The results indicate that different methods exhibit varying advantages and complexity in MPP assessment,thus constituting a multi-level assessment framework for MPP.In particular,the time-domain comprehensive assessment has a higher accuracy with more realistic description of manoeuvre behaviors,capable of offering a solution for the ships that cannot meet other assessments,or for the assessment requiring additional course-keeping ability.Furthermore,an expanded range of wave direction sets a stricter but potentially necessary requirement,while using the self-propulsion factors at low speeds can eliminate the unnecessary conservation of assessment result caused by those at design speed.
文摘For a graph G,a vertex is said to be pendant if its neighborhood contains exactly one vertex.In this paper,we determine the extremal graphs among all n-vertex graphs with the minimum spectral radius andβpendant vertices,whereβe{1,2,3,4,n-3,n-2,n-1}.
基金the National Natural Science Foundation of China(No.51965032)the Natural Science Foundation of Gansu Province(No.22JR5RA319)+1 种基金the Science and Technology Foundation of Gansu Province(No.21YF5WA060)the Excellent Doctoral Student Foundation of Gansu Province(No.23JRRA842)。
文摘Cranes used at sea have some shortcomings in terms of flexibility,efficiency,and safety.Therefore,a floating multi-robot coordinated towing system is planned to fulfill the offshore towing requirements.It is difficult to study the stability of a floating multi-robot coordinated towing system by ancient strategies.First,the minimum tension of the rope and the minimum singular value of the stiffness matrix were separately used to analyze the load stability.The advantages and disadvantages of the two methods were discussed.Then,the two stability analysis methods were normalized and weighted to obtain the method based on minimum tension and minimum singular to comprehensively analyze the stability of the load.Finally,the effect of different weighting coefficients on the load stability was analyzed,which led to a reasonable weighting coefficient to evaluate the load stability by comparing with a single analysis method.The research results provide a basis for the motion planning and coordinated control of the towing system.
基金Supported by National Natural Science Foundation of China(Grant Nos.52375447,52305477 and 52105457)Shandong Provincial Natural Science Foundation(Grant Nos.ZR2023QE057,ZR2024QE100 and ZR2024ME255)+2 种基金Qingdao Municipal Science and Technology Planning Park Cultivation Plan(Grant No.23-1-5-yqpy-17-qy)Shandong Provincial Science and Technology SMEs Innovation Capacity Improvement Project(Grant No.2022TSGC1115)the Special Fund of Taishan Scholars。
文摘As the manufacturing industry shifts toward environmentally sustainable practices,grinding—a high-precision pro-cessing method—is commonly used to ensure final workpiece dimensions and surface quality.The greening of grind-ing processes has emerged as an important challenge for both academia and industry.Numerous studies proposing different methods for sustainable grinding have increased rapidly;however,the technical mechanisms and develop-ment trends remain unclear.This paper applies bibliometric methods to analyze relevant articles published on WOS from 2008 to 2023.Results show that China has the highest number of publications(45.38%),with research institu-tions primarily located in China,India,and Brazil.Among publishing journals,70%are classified as Q2 or above.Addi-tionally,popular authors and influential articles in this field are identified.Keyword frequency and hotspot literature analysis reveal that research focuses primarily on minimal quantity lubrication(MQL)grinding,especially using biolubricants and nanoparticles to improve grinding performance.This article reviews the mechanisms and effects of biolubricants and nanoparticles in MQL.It further examines how multi-energy field applications enhance MQL by influencing droplet atomization,wettability,and machining performance.A low-temperature field improves the heat exchange capacity of MQL droplets,while an electrostatic field enhances droplet contact angles and disper-sion.Ultrasonic energy enhances the atomization of biolubricants,and magnetic fields facilitate nanoparticle penetra-tion into the grinding zone,reducing grinding forces.Additionally,innovations in grinding wheel structures and solid lubrication grinding can reduce grinding temperatures and forces.This paper presents a comprehensive review of eco-friendly grinding development hotspots,providing technical support and theoretical guidance for academia and industry.
基金supported by the following organizations:the Special Fund of Taishan Scholars Project(No.tsqn202211179)the National Natural Science Foundation of China(No.52105457)+2 种基金Young Talent of Lifting engineering for Science and Technology in Shandong,China(No.SDAST2021qt12)the National Natural Science Foundation of China(No.52375447)China Postdoctoral Science Foundation Funded Project(No.2023M732826).
文摘The use of Minimum Quantity Lubrication(MQL)with bio-lubricants has been extensively studied in aerospace sustainable manufacturing.Enhanced MQL technologies have been proposed to reduce tool wear and improve workpiece surface integrity by increasing lubricant activity.However,the relationship between enhancement behavior,physicochemical properties of biolubricants,and processability remains unclear,presenting challenges for MQL technologies,particularly with difficult-to-machine materials.To address this gap,this paper provides an in-depth mechanism analysis and a comprehensive quantitative evaluation of the machinability of enhanced MQL technologies,considering chemistry,molecular dynamics,fluid dynamics,tribology,and heat transfer.Firstly,the cooling and lubrication enhancement mechanisms of nano-lubricants were systematically summarized.focusing on molecular structure.physical properties,and preparation processes.Secondly,the atomization enhancement mechanism of Electrostatic Minimum Quantity Lubrication(EMQL)was analyzed.revealing a 49%reduction in PM2.5 concentration during the atomization process compared to conventional MQL.Thirdly,the transport and infiltration enhancement mechanisms of bio-lubricants in cutting and grinding zones were summarized,incorporating electromagnetic fields and ultrasound-assisted processes.Finally,for cutting and grinding applications involving difficult-to-machine materials in aerospace,the optimized machinability of enhanced MQL technologies was concluded,showing a 50.1%increase in lubricant heat transfer coefficient and a 31.6%decrease in grinding temperature compared to standard MQL.This paper aims to help scientists understand the effective mechanisms,formulate process specifications,and identify future development trends in this technology.
基金supported by Shandong Provincial Natural Science Foundation(No.ZR2022MF314).
文摘Conventional adaptive filtering algorithms often exhibit performance degradation when processing multipath interference in raw echoes of spaceborne synthetic aperture radar(SAR)systems due to anomalous outliers,manifesting as insufficient convergence and low estimation accuracy.To address this issue,this study proposes a novel robust adaptive filtering algorithm,namely the M-estimation-based minimum error entropy with affine projection(APMMEE)algorithm.This algorithm inherits the joint multi-data-block update mechanism of the affine projection algorithm,enabling rapid adaptation to the dynamic characteristics of raw echoes and achieving fast convergence.Meanwhile,it incorporates the M-estimation-based minimum error entropy(MMEE)criterion,which weights error samples in raw echoes through M-estimation functions,effectively suppressing outlier interference during the algorithm update.Both the system identification simulations and practical multipath interference suppression experiments using raw echoes demonstrate that the proposed APMMEE algorithm exhibits superior filtering performance.
基金supported by the National Natural Science Foundation of China(12271317,11871316)。
文摘Dengue is a mosquito-borne disease that is rampant worldwide,with up to 70%of cases reported to be asymptomatic during epidemics.In this paper,a reaction-diffusion dengue model with asymptomatic carrier transmission is investigated.We aim to study the existence,nonexistence and minimum wave speed of traveling wave solutions to the model.The results show that the existence and nonexistence of traveling wave solutions are fully determined by the threshold values,which are,the basic reproduction number R0 and critical wave speed c^(*)>0.Specifically,when R0>1 and the wave speed c≥c^(*),the existence of the traveling wave solution is obtained by using Schauder's fixed point theorem and Lyapunov functional.It is proven that the model has no nontrivial traveling wave solutions for R0≤1 or R0>1 and 0<c<c^(*)by employing comparison principle and limit theory.As a consequence,we conclude that the critical wave speed c^(*)is the minimum wave speed of the model.Finally,numerical simulations are carried out to illustrate the effects of several important parameters on the minimum wave speed.
基金funded by National Natural Science Foundation of China(Grants No.42371282 and 42130508)the Second Ti-betan Plateau Scientific Expedition and Research Program(Grant No.2019QZKK1006)Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2020055)。
文摘The interactions between fire,ecosystems,and climate are complex.Tropical ecosystems have dominated global active fires nowadays,yet its causes,mechanisms,and consequences remain relatively poorly understood.To in-vestigate temporal response of remotely-sensed active fires to intra-annual climate change,several 1-km datasets,including the Moderate-resolution Imaging Spectroradiometer Collection 6(MODIS C6)active fires and the Cli-matologies at High Resolution for the Earth’s Land Surface Areas(CHELSA)climate variables,were gathered to examine the climatic characteristics of active fire incidences,fire-climate correlations,and the average monthly response of active fire occurrences to climate change using the Geographic Information System(GIS)Fishnet tool,Theil-Sen Median slope estimation,Mann-Kendall significance test,and Pearson’s correlation.We concluded that climate variables’trends of nearly two-decade active fires displayed varied degrees of increment in precipitation(Pre),temperature(Tas),and surface downwelling shortwave radiation(Rsds)and inconsistent decrement in near-surface relative humidity(Hurs)and near-surface wind speed(sfcWind).MODIS multi-year(2003-2018)active fires were moderately to strongly correlated negatively with Pre and Hurs at 10 km grid-resolution but positively with sfcWind and Rsds,showing marked geographical variations in correlation direction and strength.The most significant finding is the newly observed inverse relationship between active fires and precipitation on both sides of the equator.High occurrence areas of active fires regularly appear back and forth along with latitudinal changes(at one-degree intervals)in monthly minimum precipitation between the tropical Northern and Southern Hemispheres.The present study contributes to exploring the underlying mechanism of fire-climate interactions against the backdrop of climate warming.
基金supported in part by the Brazilian research agencies CNPq and CAPESby the Fundação Carlos Chagas Filho de AmparoàPesquisa do Estado do Rio de Janeiro,FAPERJ-Brasil(Project E-26/210.425/2024).
文摘This paper proposes an extension of the Modified-Plant ADRC(MP-ADRC)strategy to broaden its application to minimum phase dynamical systems.The main features of the MP-ADRC method are the inclusion of a constant gain in series with the plant output error and a linear filter in parallel with the overall error system.These structural changes do not influence the input/output dynamics of the original plant,but are intentionally introduced to modify the dynamics to be estimated by the extended state observer(ESO)and,thus,promote an increase in the robustness of the method.Some advantages can also be attributed to the proposed methodology,such as(i)the design procedures of both the controller and the ESO only require knowledge of the sign(±)of the plant input channel coefficient(or control gain);(ii)the plant control input is generated directly by a single ESO state variable.Despite the advantages and the characteristics of MP-ADRC mentioned earlier,closed-loop stability cannot be guaranteed when it is applied to dynamical systems that have finite zeros.To overcome this difficulty,this work introduces an extension in the MP-ADRC method.It basically consists of rewriting the minimum phase plant dynamics according to its relative order,and then follows with the design of the ESO by conveniently increasing the number of ESO state variables.The simulation results are also presented to illustrate the application of the proposed method.
