A Storm Water Pumping Station funded by the World Bank is under construction and commissioning,of which the earthing system design is a crucial part for the electrical design.Based on IEEE and BS standards,this articl...A Storm Water Pumping Station funded by the World Bank is under construction and commissioning,of which the earthing system design is a crucial part for the electrical design.Based on IEEE and BS standards,this article fully introduces the analysis methodology and calculation of the system within the framework of the World Bank supported project.A solution of this practical case satisfied with the requirements of international standards is shown in order to bring experience and convenience for engineers who are dedicated to projects abroad.展开更多
This paper presents and tests three earthing systems (TT, TN and IT) for Micro-Grid (MG) protection against various fault types when the MG transferred to the islanding mode. The main contribution of this work is incl...This paper presents and tests three earthing systems (TT, TN and IT) for Micro-Grid (MG) protection against various fault types when the MG transferred to the islanding mode. The main contribution of this work is including the models of all micro sources which interfaced to the MG by power electronic inverters. Inverters in turns are provided with current limiters and this also included with the inverter models to exactly simulate the real situation in the MG during fault times. Results proved that the most suitable earthing system for MG protection during the islanding mode is the TN earthing system. That system leads to a suitable amount of fault current sufficient to activate over current pro-tection relays. With using TN earthing system, touch voltages at the faulted bus and all other consumer’s buses are less than the safety limited values during islanding mode. For the two others earthing systems (TT and IT), fault currents are small and nearly equal to the over load currents which make over current protection relay can not differentiate between fault currents and overload currents. All models of micro sources, earthing systems, inverters and control schemes are built using Matlab?/Simulink? environment.展开更多
This paper presents, tests and compares three earthing systems (TT, TN and IT) for Micro-Grid (MG) protection against various fault types during the connected mode. The main contribution of this work is including the ...This paper presents, tests and compares three earthing systems (TT, TN and IT) for Micro-Grid (MG) protection against various fault types during the connected mode. The main contribution of this work is including the models of all the micro sources which interfaced to the MG by power electronic inverters. Inverters in turns are provided with current limiters and this also included in the inverter models to exactly simulate the real situation in the MG during fault times. Results proved that the most suitable earthing system for MG protection during the connecting mode is the TN earthing system. That system leads to a suitable amount of fault current sufficient to activate over current protection relays. With using TN system, Touch voltages at the faulted bus and all other consumer’s buses are less than the safety limited value if current limiter is included with the transformer of the main grid which connects MG. For the two others earthing systems (TT and IT), fault current is small and nearly equal to the over load current which make over current protection relay can not differentiate between fault current and overload current. All models of micro sources, earthing systems, inverters, main grid and control schemes are built using Matlab?/Simulink? environment.展开更多
The UHVDC transmission line transports large-capacity power, and its safety operation has very important rule on the safe operation of grid. Currently, in the DC transmission system, the earthing electrode line has th...The UHVDC transmission line transports large-capacity power, and its safety operation has very important rule on the safe operation of grid. Currently, in the DC transmission system, the earthing electrode line has the functions of ground potential fixing and bipolar imbalance current circulation during the operation of bipolar balance. Therefore the monitoring to the earthing electrode line operation is very essential. This article firstly introduced the current situation of the research on the earthing electrode line fault location method, then built the relevant PSCAD/EMTDC model for simulation verification of the current using Time Domain Reflectometry for the UHVDC earthing electrode line, and at last analyzed the reasons for the formation of the blind monitoring zones.展开更多
The rail weighbridge system of a railway freight station is introduced firstly, and then the earthing method for protection of the rail weighbridge system against lightning based on YLG-60 equipotential bonding surge ...The rail weighbridge system of a railway freight station is introduced firstly, and then the earthing method for protection of the rail weighbridge system against lightning based on YLG-60 equipotential bonding surge protection device is shown.展开更多
The reaction of carbon-free oxide-based(corundum,spinel,zirconia,and mullite)submerged entry nozzle(SEN)lining with rare earth inclusions and its anti-clogging effects under near working conditions were systematically...The reaction of carbon-free oxide-based(corundum,spinel,zirconia,and mullite)submerged entry nozzle(SEN)lining with rare earth inclusions and its anti-clogging effects under near working conditions were systematically studied.A variety of lining composite test methods were innovatively used to ensure the consistency of test conditions.The experimental results showed that the mullite(acidic oxide)has strong reactivity with rare earth inclusions,and the spinel(basic oxide)has stable chemical properties and weak reactivity with rare earth inclusions.Because alumina is one of the main reactants of clogging formation,corundum is not suitable for SEN lining.There are less clogs on the surface of zirconia,but it will be exsoluted and unstable.Therefore,solving the problem of zirconia exsolution will greatly strengthen its application in SEN lining.展开更多
The magnesium based metal hydrogen storage composite system Mg(NH_(2))_(2)-2LiH has a theoretical hydro-gen storage capacity of 5.6 wt.%and is a promising hydrogen storage material for vehicles.However,its application...The magnesium based metal hydrogen storage composite system Mg(NH_(2))_(2)-2LiH has a theoretical hydro-gen storage capacity of 5.6 wt.%and is a promising hydrogen storage material for vehicles.However,its application is limited due to serious thermodynamic and kinetic barriers.Introducing efficient catalysts is an effective method to improve the hydrogen storage performance of Mg(NH_(2))_(2)-2LiH.This article in-vestigates for the first time the use of nano rare earth oxide CeO_(2)(~44.5 nm)as an efficient modifier,achieving comprehensive regulation of the hydrogen storage performance of Mg(NH_(2))_(2)-2LiH composite system through oxygen vacancy driven catalysis.The modification mechanism of nano CeO_(2) is also sys-tematically studied using density functional theory(DFT)calculations and experimental results.Research has shown that the comprehensive hydrogen storage performance of the Mg(NH_(2))_(2)-2LiH-5 wt.%CeO_(2) composite system is optimal,with high hydrogen absorption and desorption kinetics and reversible per-formance.The initial hydrogen absorption and desorption temperatures of the composite system were significantly reduced from 110/130℃to 65/80℃,and the release of by-product ammonia was signifi-cantly inhibited.Under the conditions of 170℃/50 min and 180℃/100 min,4.37 wt.%of hydrogen can be rapidly absorbed and released.After 10 cycles of hydrogen release,the hydrogen cycle retention rate increased from 85%to nearly 100%.Further mechanistic studies have shown that the nano CeO_(2-x) gen-erated in situ during hydrogen evolution can effectively weaken the Mg-N and N-H bonds of Mg(NH_(2))_(2),exhibiting good catalytic effects.Meanwhile,oxygen vacancies provide a fast pathway for the diffusion of hydrogen atoms in the composite system.In addition,nano CeO_(2-x) can effectively inhibit the polycrys-talline transformation of the hydrogen evolving product Li_(2)MgN_(2)H_(2) in the system at high temperatures,reducing the difficulty of re-hydrogenation of the system.This study provides an innovative perspective for the efficient modification of magnesium based metal hydrogen storage composite materials using rare earth based catalysts,and also provides a reference for regulating the comprehensive hydrogen storage performance of hydrogen storage materials using rare earth catalysts with oxygen vacancies.展开更多
The recovery of rare earths from industrial rare earth leaching solution is typically achieved through the ammonium carbonate precipitation method,which presents challenges in terms of prolonged production cycle and a...The recovery of rare earths from industrial rare earth leaching solution is typically achieved through the ammonium carbonate precipitation method,which presents challenges in terms of prolonged production cycle and ammonia nitrogen pollution.The present study explored the synthesis of crystalline yttrium carbonate in a sodium carbonate system,employing a conventional mother liquor derived from yttrium chloride.The growth of yttrium carbonate was explored through the lens of density functional theory(DFT)calculations,unveiling a novel perspective on its formation mechanism.The synthesized yttrium carbonate demonstrates enhanced crystallinity,with a D50value of 19.75μm achieved under reaction conditions comprising a temperature of 60℃,stirring rate of 200 r/min,feeding rate of 4 mL/min,and aging time of 30 h.The molar ratio for precipitation is set at 1.6:1.The morphology of yttrium carbonate undergoes a transition from needle-like structures to sheet-like formations,ultimately culminating in the formation of spherical aggregates.The variation in surface energy among distinct crystal planes and CO_(3)^(2-)configurations within crystal cells accounts for this phenomenon.The DFT calculations unveil a progression of growth and trans formation in yttrium carbonate,commencing from a one-dimensional configuration and culminating in a multidimensional morphology.展开更多
This study details a comprehensive approach focusing on the effective separation of light rare earth elements(REEs)via solvent extraction technique.A stock solution containing lanthanum,cerium,neodymium,praseodymium,a...This study details a comprehensive approach focusing on the effective separation of light rare earth elements(REEs)via solvent extraction technique.A stock solution containing lanthanum,cerium,neodymium,praseodymium,and samarium was prepared by dissolving their pure mixed oxide(reclaimed from spent Ni-MH batteries)in a diluted HCl solution.Key extractants,including bis(2,4,4-trimethylpentyl)phosphinic acid(Cyanex 272),Cyanex 572,trialkylphosphine oxide(Cyanex 923),and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester(PC 88A),along with tributyl phosphate(TBP)as a phase modifier,were utilized to form organic systems.The extraction behavior and separability of these systems at various pH levels as well as their extraction mechanisms were investigated.The results demonstrated a direct relationship between the extraction trend and the experimental pH value,with enhanced selectivity when TBP was added.Notably,Nd and Pr exhibited similar extraction behaviors,with minor deviations from Ce,making their separation difficult to achieve.Sm extraction followed a distinct trend,allowing for its separation from other elements at pH≤2.In contrast,La exhibited a low affinity for coordination with extractants when pH was≤3.5,facilitating the separation of other elements from La,which could then be isolated in the raffinate.Among the studied organic systems,combinations of Cyanex 572 and PC 88A with TBP demonstrated superior performance in element separation.Optimum separation factors were calculated withβ_(Ce/La)=12,βNd/La=87,β_(Pr/La)=127,andβ_(Sm/La)=3191 for the former,andβ_(Sm/Ce)=54,β_(Sm/Nd)=20,andβ_(Sm/Pr)=14 for the latter.These findings provide valuable insights for selecting extraction systems and designing experiments for the effective solvent extraction separation of light REEs from their mixture.展开更多
The Vietnamese Mekong Delta(VMD),a critical agricultural hub,faces recurrent flooding that poses substantial threats to livelihoods and productivity.Ben Tre province,with its low-lying coastal terrain,is particularly ...The Vietnamese Mekong Delta(VMD),a critical agricultural hub,faces recurrent flooding that poses substantial threats to livelihoods and productivity.Ben Tre province,with its low-lying coastal terrain,is particularly vulnerable.Effective risk management and sustainable agricultural development necessitate a thorough understanding of these flood dynamics.This study leveraged the Google Earth Engine(GEE)platform and Sentinel-1 Synthetic Aperture Radar(SAR)imagery to analyze flood inundation patterns and their impacts on diverse agricultural land uses in Ben Tre province from 2015 to 2023.The methodology involved SAR data pre-processing,Otsu thresholding for water body delineation from VH polarization data and change detection using a 2020 land use map to quantify annual flooded areas and their impact on specific agricultural categories.The total inundated area peaked in 2018 at 58,334 ha,a significant increase from 27,934 ha in 2015,before stabilizing around 42,000–44,000 ha in 2021–2023.Flooded agricultural land mirrored this trend,increasing from 18,615 ha(2015)to a peak of 39,514 ha(2018),then decreasing to 28,841 ha(2023).Notably,wet rice cultivation experienced a 37.8%increase in its flooded area over the study period,while other annual crops and perennial crops saw increases of 38.9% and 68.4%,respectively.This research demonstrates the GEE platform’s efficacy with Sentinel-1 SAR for robust,long-term flood monitoring and impact assessment,revealing escalating flood pressure on key agricultural systems and an expansion of flooding beyond traditional low-lying zones,providing crucial data for adaptive land use planning.展开更多
In this work,Au loading and micro-morphology regulation were used to synergistically enhance the gas sensing properties of LaFeO_(3)-based materials.2 wt%Au:LaFeO_(3)prepared by electrostatic spinning method has a res...In this work,Au loading and micro-morphology regulation were used to synergistically enhance the gas sensing properties of LaFeO_(3)-based materials.2 wt%Au:LaFeO_(3)prepared by electrostatic spinning method has a response of 38.26 for 1 ppm H_(2)S and 5.32 for 1 ppm HCHO at 120℃.Over a one-month period,the response of 2 wt%Au:LaFeO_(3)decreases by just 0.52%for H_(2)S and 2.07%for HCHO,demonstrating excellent long-term stability.Additionally,for H_(2)S and HCHO at concentrations ranging from 0.1to 1 ppm,all the response-recovery time is within 40 s.2 wt%Au:LaFeO_(3)also shows excellent gas selectivity and humidity resistance.This outstanding gas sensing performance might be attributed to the catalytic sensitization effect of Au NPs,as well as the largest specific surface area,porosity,and the smallest grain size of 2 wt%Au:LaFeO_(3)hollow nanotube.To further enhance gas selectivity and recognition capability of 2 wt%Au:LaFeO_(3)for H_(2)S and HCHO,a machine learning model combining a backpropagation(BP)neural network with response-recovery feature data extracted through principal component analysis(PCA)was trained.This model accurately identified and detected individual gases in a mixture of H_(2)S and HCHO,with an error rate of less than 10%.This work demonstrates the synergistic enhancement of gas sensing properties through Au loading and micro-morphology regulation,offering a novel approach for detecting and identifying gases with cross-responsiveness using non-sensor arrays.展开更多
The health of cropland systems is directly related to the degree of food security guarantee,and the‘quantity-quality-ecology as a whole’protection is of great significance for maintaining the health of cropland syst...The health of cropland systems is directly related to the degree of food security guarantee,and the‘quantity-quality-ecology as a whole’protection is of great significance for maintaining the health of cropland systems.Taking the typical black soil region in Northeast China(TBSN)as an example,this paper combined the concept of‘quantity-quality-ecology as a whole’protection with crop-land systems health,constructed a health assessment model for cropland systems,and used Google Earth Engine to conduct a quantitat-ive analysis of the temporal and spatial evolution of cropland systems health in TBSN during 2003–2023.By coupling the geographical detector and the Multi-scale Geographically Weighted Regression(MGWR)model,the driving factors of cropland health changes were explored.The study finds that during the research period,the health status of cropland systems in TBSN showed a slight downward trend,and the distribution pattern of cropland systems health gradually shifted from‘better in the east’to‘high in the northeast and low in the southwest’.Changes in average annual sunshine duration,relative humidity,and precipitation had a significant impact on the spa-tial differentiation of cropland systems health in the early stages,and were considered as dominant factors.Meanwhile,the influence of dual dominant factors in the natural environment on cropland systems health is increasing.Furthermore,the MGWR model performed better in revealing the complex relationships between natural and social factors and changes in cropland systems health,demonstrating the significant spatial heterogeneity of the impacts of natural environment and human activities on cropland systems health.The re-search can provide scientific guidance for the sustainable development of TBSN and formulate more precise and effective cropland pro-tection policies.展开更多
This review provides a comprehensive overview of recent advancements in aluminum-based conductor alloys engineered to achieve superior mechanical strength and thermal stability without sacrificing electrical conductiv...This review provides a comprehensive overview of recent advancements in aluminum-based conductor alloys engineered to achieve superior mechanical strength and thermal stability without sacrificing electrical conductivity.Particular emphasis is placed on the role of microalloying elements—particularly Sc and Zr-in promoting the formation of coherent nanoscale precipitates such as Al_(3)Zr,Al_(3)Sc,and core-shell Al_(3)(Sc,Zr)with metastable L1_(2)crystal structures.These precipitates contribute significantly to high-temperature performance by enabling precipitation strengthening and stabilizing grain boundaries.The review also explores the emerging role of other rare earth elements(REEs),such as erbium(Er),in accelerating precipitation kinetics and improving thermal stability by retarding coarsening.Additionally,recent advancements in thermomechanical processing strategies are examined,with a focus on scalable approaches to optimize the strength-conductivity balance.These approaches involve multi-step heat treatments and carefully controlled manufacturing sequences,particularly the combination of cold drawing and aging treatment to promote uniform and effective precipitation.This review offers valuable insights to guide the development of cost-effective,high-strength,heat-resistant aluminum alloys beyond conductor applications,particularly those strengthened through microalloying with Sc and Zr.展开更多
We report a theoretical investigation into superconductivity within the MAXH_(6) quaternary hydride system using first-principles calculations,where M and A denote alkali and alkaline earth elements,respectively,and X...We report a theoretical investigation into superconductivity within the MAXH_(6) quaternary hydride system using first-principles calculations,where M and A denote alkali and alkaline earth elements,respectively,and X represents transition metal elements.Systematic analysis of electronic band structures,phonon dispersions,and electron-phonon coupling reveals that substitution of MA binary metal combinations and X metal atoms can create favorable conditions for superconductivity.Mapping of superconducting critical temperatures,combined with dynamical stability analysis through phonon calculations,identifies ten superconducting candidates at ambient pressure.Among these,LiNaAgH_(6) exhibits nearly-free-electron behavior reminiscent of monovalent electron superconductors.It demonstrates exceptional superconducting properties with electron–phonon coupling λ=2.707,which yields a superconducting transition temperature T_(c) of 206.4 K using the Allen–Dynes formula.Its structural analogs MgNaPdH_(6),LiMgPdH_(6),LiMgAgH_(6),LiMgAuH_(6) all exhibit superconducting transition temperatures above 110 K.These findings advance our fundamental understanding of superconductivity in quaternary hydrides and provide guidance for rational design of new high-temperature superconducting materials.展开更多
Higher strength is always the goal pursued by researchers for the structural materials,especially for the lightweight magnesium(Mg)alloys which generally have relatively low strength at present.From this aspect,the pr...Higher strength is always the goal pursued by researchers for the structural materials,especially for the lightweight magnesium(Mg)alloys which generally have relatively low strength at present.From this aspect,the present paper reviews the recent reports of a kind of Mg alloys,i.e.Mg-RE(RE:rare earths,mainly Gd or Y)casting and wrought alloys,which have been able to achieve high strength compared with common or commercial Mg alloys,from the viewpoint and content of the alloy system,alloying constitution,preparation process,tensile strength and each of the main strengthening mechanisms.This review of recent research and developments in high-strength Mg-RE alloys is beneficial for the further design of Mg alloys with higher strength as well as excellent comprehensive performance.展开更多
The current recovery technique of Sc was complicated and the chemical consumption was high,This was due to the low content of Sc in resources and the difficulty of stripping.In this research,the isooctanol was added i...The current recovery technique of Sc was complicated and the chemical consumption was high,This was due to the low content of Sc in resources and the difficulty of stripping.In this research,the isooctanol was added into the 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester(P507)extraction system to reduce the extraction and improve the stripping of Sc.The maximum stripping ratio of Sc from loaded organic phase by sulfuric acid can increase from 10%(without isooctanol)to 99%(with 15 vol%isooctanol).In the extraction test of the simulated red mud leaching liquor,the separation factors between Sc and Zr,Sc and Ti are 36 and 350,separately.At the same time,other metals are almost not extracted.The high selectivity and stripping of Sc suggest that the P507 with isooctanol extraction system can be applied in the practical Sc recovery process.展开更多
In order to solve the problem of ammonia-nitrogen pollution in the enrichment process of the ionadsorption type rare earth ore,the technology of non-ammonia precipitation with magnesium oxide precipitant was carried o...In order to solve the problem of ammonia-nitrogen pollution in the enrichment process of the ionadsorption type rare earth ore,the technology of non-ammonia precipitation with magnesium oxide precipitant was carried out.It is determined that the rare earth precipitation efficiency is 99.6%and the purity of rare earth concentrates is only 85.89 wt%under the optimum precipitation conditions.And the contents of MgO,SO3 and Al2O3 in the rare earth concentrates are 5.12 wt%,6.77 wt%and 1.78 wt%,respectively.Furthermore,the thermo-decomposition process of precipitates was investigated by TGDSC,XRD and FI-IR.The thermal decomposition process consists of two stages:the dehydration of rare earth hydroxide and alkaline rare earth sulfate within 900℃and the thermal decomposition of RE2O2SO4 at 900-1300℃.Therefore,a high-temperature calcinations method for removing SO3 from precipitates is proposed.When the precipitates are calcined at 1300℃for 2 h,the rare earth concentrates with a purity of 92.03 wt%can be acquired.Moreover,the content of SO3 in the concentrate is only 0.46 wt%.In the MgO precipitation and high-temperature calcinations process,the raw material cost is low and the quality of rare earth concentrates is acceptable.It could have great significance for nonammonia enrichment of rare earth from the rare earth leaching liquor,and finally solve the problem of ammonia nitrogen in the extraction process of the ion-adsorption type rare earth ore within magnesium salt system.展开更多
Compelling evidence indicates that the solid Earth consists of two physicochemically distinct zones separated radially in the middle of the lower mantle at∼1800 km depth.The inner zone is governed by pressure-induced...Compelling evidence indicates that the solid Earth consists of two physicochemically distinct zones separated radially in the middle of the lower mantle at∼1800 km depth.The inner zone is governed by pressure-induced physics and chemistry dramatically different from the conventional behavior in the outer zone.These differences generate large physical and chemical potentials between the two zones that provide fundamental driving forces for triggering major events in Earth’s history.One of the main chemical carriers between the two zones isH_(2)Oin hydrous minerals that subducts into the inner zone,releases hydrogen,and leaves oxygen to create superoxides and form oxygen-rich piles at the core–mantle boundary,resulting in localized net oxygen gain in the inner zone.Accumulation of oxygen-rich piles at the base of the mantle could eventually reach a supercritical level that triggers eruptions,injecting materials that cause chemical mantle convection,superplumes,large igneous provinces,extreme climate changes,atmospheric oxygen fluctuations,and mass extinctions.Interdisciplinary research will be the key for advancing a unified theory of the four-dimensional Earth system.展开更多
Emulsification troubled normal extraction process of rare earths due to the existence of non-rare earth impurities, especially Si, Al and Fe. Against this background, the effect of emulsification caused by Si, Al and ...Emulsification troubled normal extraction process of rare earths due to the existence of non-rare earth impurities, especially Si, Al and Fe. Against this background, the effect of emulsification caused by Si, Al and Fe on the La extraction with saponification P507 （2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester） in chloride medium was systematically investigated. A series of experiments were carried out to study the relationship of the extraction capacity of La and the concentration of impurities. ZPM-203 polarizing microscope was applied to investigate the morphology of emulsification, and the cation exchange extraction mechanism of Fe and Al as well as La was clarified by IR spectra. The results showed that a low concentration of Si in organic phase would aggravate the emulsification with Al, and the formation of ME （micro emulsion） and club-shaped polymer would result in emulsification in the extraction of mixtures of Si and Al, single Fe, respectively. Furthermore, the accumulation of impurity such as Si, Al and Fe in the organic phase would severely reduce the extraction capacity of La simultaneously.展开更多
After treated with low concentration of La^3 ＋ , the rate of producing active oxygen free radical, the relative permeability of cell membrane, the contents of bivalent iron ion in wheat seedling leaves under water st...After treated with low concentration of La^3 ＋ , the rate of producing active oxygen free radical, the relative permeability of cell membrane, the contents of bivalent iron ion in wheat seedling leaves under water stress were determined. The results show that in wheat seedling leaves, feasible concentrations of La^3 ＋ decreases the accumulation of active oxygen free radical, inhibits the increase of the relative permeability of cell membrane, reduces the content of peroxidation product MDA of membrane lipid, and prevents the plant cell producing more bivalent iron ion which can catalyzed the reaction of Haber-weiss and Fenton to produce more superoxide anion. In addition, purified plasma membrane was isolated by aqueous two-phase partitioning from wheat seedling leaves. The reduction rate of Fe（CN）6^3- by purified plasma membrane in La^3＋ -treated wheat seedling leaves is different from those in the absence of La^3＋ under water stress. The changing trend of the redox activity to La^3＋ is similar to that of the content of Fe^2＋ . The results reveal that extraneous La^3＋ can alleviate the damages of cell membrane caused by water stress via promoting the activity of redox system and the ability of eliminating ROS in wheat seedling leaves.展开更多
文摘A Storm Water Pumping Station funded by the World Bank is under construction and commissioning,of which the earthing system design is a crucial part for the electrical design.Based on IEEE and BS standards,this article fully introduces the analysis methodology and calculation of the system within the framework of the World Bank supported project.A solution of this practical case satisfied with the requirements of international standards is shown in order to bring experience and convenience for engineers who are dedicated to projects abroad.
文摘This paper presents and tests three earthing systems (TT, TN and IT) for Micro-Grid (MG) protection against various fault types when the MG transferred to the islanding mode. The main contribution of this work is including the models of all micro sources which interfaced to the MG by power electronic inverters. Inverters in turns are provided with current limiters and this also included with the inverter models to exactly simulate the real situation in the MG during fault times. Results proved that the most suitable earthing system for MG protection during the islanding mode is the TN earthing system. That system leads to a suitable amount of fault current sufficient to activate over current pro-tection relays. With using TN earthing system, touch voltages at the faulted bus and all other consumer’s buses are less than the safety limited values during islanding mode. For the two others earthing systems (TT and IT), fault currents are small and nearly equal to the over load currents which make over current protection relay can not differentiate between fault currents and overload currents. All models of micro sources, earthing systems, inverters and control schemes are built using Matlab?/Simulink? environment.
文摘This paper presents, tests and compares three earthing systems (TT, TN and IT) for Micro-Grid (MG) protection against various fault types during the connected mode. The main contribution of this work is including the models of all the micro sources which interfaced to the MG by power electronic inverters. Inverters in turns are provided with current limiters and this also included in the inverter models to exactly simulate the real situation in the MG during fault times. Results proved that the most suitable earthing system for MG protection during the connecting mode is the TN earthing system. That system leads to a suitable amount of fault current sufficient to activate over current protection relays. With using TN system, Touch voltages at the faulted bus and all other consumer’s buses are less than the safety limited value if current limiter is included with the transformer of the main grid which connects MG. For the two others earthing systems (TT and IT), fault current is small and nearly equal to the over load current which make over current protection relay can not differentiate between fault current and overload current. All models of micro sources, earthing systems, inverters, main grid and control schemes are built using Matlab?/Simulink? environment.
文摘The UHVDC transmission line transports large-capacity power, and its safety operation has very important rule on the safe operation of grid. Currently, in the DC transmission system, the earthing electrode line has the functions of ground potential fixing and bipolar imbalance current circulation during the operation of bipolar balance. Therefore the monitoring to the earthing electrode line operation is very essential. This article firstly introduced the current situation of the research on the earthing electrode line fault location method, then built the relevant PSCAD/EMTDC model for simulation verification of the current using Time Domain Reflectometry for the UHVDC earthing electrode line, and at last analyzed the reasons for the formation of the blind monitoring zones.
文摘The rail weighbridge system of a railway freight station is introduced firstly, and then the earthing method for protection of the rail weighbridge system against lightning based on YLG-60 equipotential bonding surge protection device is shown.
基金supported by the National Outstanding Youth Science Fund Project of National Natural Science Foundation of China(52302031)National Natural Science Foundation of China(51932008 and 51772277)Central China Thousand Talents Project(204200510011).
文摘The reaction of carbon-free oxide-based(corundum,spinel,zirconia,and mullite)submerged entry nozzle(SEN)lining with rare earth inclusions and its anti-clogging effects under near working conditions were systematically studied.A variety of lining composite test methods were innovatively used to ensure the consistency of test conditions.The experimental results showed that the mullite(acidic oxide)has strong reactivity with rare earth inclusions,and the spinel(basic oxide)has stable chemical properties and weak reactivity with rare earth inclusions.Because alumina is one of the main reactants of clogging formation,corundum is not suitable for SEN lining.There are less clogs on the surface of zirconia,but it will be exsoluted and unstable.Therefore,solving the problem of zirconia exsolution will greatly strengthen its application in SEN lining.
基金supported by the National Natural Science Foundation of China(Nos.51971199 and 51771171).
文摘The magnesium based metal hydrogen storage composite system Mg(NH_(2))_(2)-2LiH has a theoretical hydro-gen storage capacity of 5.6 wt.%and is a promising hydrogen storage material for vehicles.However,its application is limited due to serious thermodynamic and kinetic barriers.Introducing efficient catalysts is an effective method to improve the hydrogen storage performance of Mg(NH_(2))_(2)-2LiH.This article in-vestigates for the first time the use of nano rare earth oxide CeO_(2)(~44.5 nm)as an efficient modifier,achieving comprehensive regulation of the hydrogen storage performance of Mg(NH_(2))_(2)-2LiH composite system through oxygen vacancy driven catalysis.The modification mechanism of nano CeO_(2) is also sys-tematically studied using density functional theory(DFT)calculations and experimental results.Research has shown that the comprehensive hydrogen storage performance of the Mg(NH_(2))_(2)-2LiH-5 wt.%CeO_(2) composite system is optimal,with high hydrogen absorption and desorption kinetics and reversible per-formance.The initial hydrogen absorption and desorption temperatures of the composite system were significantly reduced from 110/130℃to 65/80℃,and the release of by-product ammonia was signifi-cantly inhibited.Under the conditions of 170℃/50 min and 180℃/100 min,4.37 wt.%of hydrogen can be rapidly absorbed and released.After 10 cycles of hydrogen release,the hydrogen cycle retention rate increased from 85%to nearly 100%.Further mechanistic studies have shown that the nano CeO_(2-x) gen-erated in situ during hydrogen evolution can effectively weaken the Mg-N and N-H bonds of Mg(NH_(2))_(2),exhibiting good catalytic effects.Meanwhile,oxygen vacancies provide a fast pathway for the diffusion of hydrogen atoms in the composite system.In addition,nano CeO_(2-x) can effectively inhibit the polycrys-talline transformation of the hydrogen evolving product Li_(2)MgN_(2)H_(2) in the system at high temperatures,reducing the difficulty of re-hydrogenation of the system.This study provides an innovative perspective for the efficient modification of magnesium based metal hydrogen storage composite materials using rare earth based catalysts,and also provides a reference for regulating the comprehensive hydrogen storage performance of hydrogen storage materials using rare earth catalysts with oxygen vacancies.
基金Project supported by the National Natural Science Foundation of China(52174250,92062110)the Youth Jinggang Scholars Program in Jiangxi Province(QNJG2020048)。
文摘The recovery of rare earths from industrial rare earth leaching solution is typically achieved through the ammonium carbonate precipitation method,which presents challenges in terms of prolonged production cycle and ammonia nitrogen pollution.The present study explored the synthesis of crystalline yttrium carbonate in a sodium carbonate system,employing a conventional mother liquor derived from yttrium chloride.The growth of yttrium carbonate was explored through the lens of density functional theory(DFT)calculations,unveiling a novel perspective on its formation mechanism.The synthesized yttrium carbonate demonstrates enhanced crystallinity,with a D50value of 19.75μm achieved under reaction conditions comprising a temperature of 60℃,stirring rate of 200 r/min,feeding rate of 4 mL/min,and aging time of 30 h.The molar ratio for precipitation is set at 1.6:1.The morphology of yttrium carbonate undergoes a transition from needle-like structures to sheet-like formations,ultimately culminating in the formation of spherical aggregates.The variation in surface energy among distinct crystal planes and CO_(3)^(2-)configurations within crystal cells accounts for this phenomenon.The DFT calculations unveil a progression of growth and trans formation in yttrium carbonate,commencing from a one-dimensional configuration and culminating in a multidimensional morphology.
基金support from the Australian Research Council’s Industrial Transformation Research Hub funding scheme(project IH190100009).
文摘This study details a comprehensive approach focusing on the effective separation of light rare earth elements(REEs)via solvent extraction technique.A stock solution containing lanthanum,cerium,neodymium,praseodymium,and samarium was prepared by dissolving their pure mixed oxide(reclaimed from spent Ni-MH batteries)in a diluted HCl solution.Key extractants,including bis(2,4,4-trimethylpentyl)phosphinic acid(Cyanex 272),Cyanex 572,trialkylphosphine oxide(Cyanex 923),and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester(PC 88A),along with tributyl phosphate(TBP)as a phase modifier,were utilized to form organic systems.The extraction behavior and separability of these systems at various pH levels as well as their extraction mechanisms were investigated.The results demonstrated a direct relationship between the extraction trend and the experimental pH value,with enhanced selectivity when TBP was added.Notably,Nd and Pr exhibited similar extraction behaviors,with minor deviations from Ce,making their separation difficult to achieve.Sm extraction followed a distinct trend,allowing for its separation from other elements at pH≤2.In contrast,La exhibited a low affinity for coordination with extractants when pH was≤3.5,facilitating the separation of other elements from La,which could then be isolated in the raffinate.Among the studied organic systems,combinations of Cyanex 572 and PC 88A with TBP demonstrated superior performance in element separation.Optimum separation factors were calculated withβ_(Ce/La)=12,βNd/La=87,β_(Pr/La)=127,andβ_(Sm/La)=3191 for the former,andβ_(Sm/Ce)=54,β_(Sm/Nd)=20,andβ_(Sm/Pr)=14 for the latter.These findings provide valuable insights for selecting extraction systems and designing experiments for the effective solvent extraction separation of light REEs from their mixture.
基金funded by the University of Science,VNU-HCM under grant number T2023-107.
文摘The Vietnamese Mekong Delta(VMD),a critical agricultural hub,faces recurrent flooding that poses substantial threats to livelihoods and productivity.Ben Tre province,with its low-lying coastal terrain,is particularly vulnerable.Effective risk management and sustainable agricultural development necessitate a thorough understanding of these flood dynamics.This study leveraged the Google Earth Engine(GEE)platform and Sentinel-1 Synthetic Aperture Radar(SAR)imagery to analyze flood inundation patterns and their impacts on diverse agricultural land uses in Ben Tre province from 2015 to 2023.The methodology involved SAR data pre-processing,Otsu thresholding for water body delineation from VH polarization data and change detection using a 2020 land use map to quantify annual flooded areas and their impact on specific agricultural categories.The total inundated area peaked in 2018 at 58,334 ha,a significant increase from 27,934 ha in 2015,before stabilizing around 42,000–44,000 ha in 2021–2023.Flooded agricultural land mirrored this trend,increasing from 18,615 ha(2015)to a peak of 39,514 ha(2018),then decreasing to 28,841 ha(2023).Notably,wet rice cultivation experienced a 37.8%increase in its flooded area over the study period,while other annual crops and perennial crops saw increases of 38.9% and 68.4%,respectively.This research demonstrates the GEE platform’s efficacy with Sentinel-1 SAR for robust,long-term flood monitoring and impact assessment,revealing escalating flood pressure on key agricultural systems and an expansion of flooding beyond traditional low-lying zones,providing crucial data for adaptive land use planning.
基金Project supported by National Natural Science Foundation of China(22306070,62374112)Shandong Provincial Natural Science Foundation(ZR2021QE265,ZR2023QB002)+3 种基金Shandong Top Talent Special Foundation(0031504)the National Key Research and Development Program of China(2022YFE0105800)Zhejiang Provincial Huzhou Science and Technology Project(2023GZ60)Open Research Fund Program of State Environmental Protection Key Laboratory of Food Chain Pollution Control(FC2022YB05,FC2022YB03)。
文摘In this work,Au loading and micro-morphology regulation were used to synergistically enhance the gas sensing properties of LaFeO_(3)-based materials.2 wt%Au:LaFeO_(3)prepared by electrostatic spinning method has a response of 38.26 for 1 ppm H_(2)S and 5.32 for 1 ppm HCHO at 120℃.Over a one-month period,the response of 2 wt%Au:LaFeO_(3)decreases by just 0.52%for H_(2)S and 2.07%for HCHO,demonstrating excellent long-term stability.Additionally,for H_(2)S and HCHO at concentrations ranging from 0.1to 1 ppm,all the response-recovery time is within 40 s.2 wt%Au:LaFeO_(3)also shows excellent gas selectivity and humidity resistance.This outstanding gas sensing performance might be attributed to the catalytic sensitization effect of Au NPs,as well as the largest specific surface area,porosity,and the smallest grain size of 2 wt%Au:LaFeO_(3)hollow nanotube.To further enhance gas selectivity and recognition capability of 2 wt%Au:LaFeO_(3)for H_(2)S and HCHO,a machine learning model combining a backpropagation(BP)neural network with response-recovery feature data extracted through principal component analysis(PCA)was trained.This model accurately identified and detected individual gases in a mixture of H_(2)S and HCHO,with an error rate of less than 10%.This work demonstrates the synergistic enhancement of gas sensing properties through Au loading and micro-morphology regulation,offering a novel approach for detecting and identifying gases with cross-responsiveness using non-sensor arrays.
基金Under the auspices of National Natural Science Foundation Youth Fund Project(No.41701424)Open Research Fund of State Key Laboratory of Remote Sensing Science(No.OFSLRSS201716)+1 种基金Jilin Province Science and Technology Development Plan Project(No.20240701167FG)Science and Technology Research Project of Education Department of Jilin Province(No.JJKH20230502KJ)。
文摘The health of cropland systems is directly related to the degree of food security guarantee,and the‘quantity-quality-ecology as a whole’protection is of great significance for maintaining the health of cropland systems.Taking the typical black soil region in Northeast China(TBSN)as an example,this paper combined the concept of‘quantity-quality-ecology as a whole’protection with crop-land systems health,constructed a health assessment model for cropland systems,and used Google Earth Engine to conduct a quantitat-ive analysis of the temporal and spatial evolution of cropland systems health in TBSN during 2003–2023.By coupling the geographical detector and the Multi-scale Geographically Weighted Regression(MGWR)model,the driving factors of cropland health changes were explored.The study finds that during the research period,the health status of cropland systems in TBSN showed a slight downward trend,and the distribution pattern of cropland systems health gradually shifted from‘better in the east’to‘high in the northeast and low in the southwest’.Changes in average annual sunshine duration,relative humidity,and precipitation had a significant impact on the spa-tial differentiation of cropland systems health in the early stages,and were considered as dominant factors.Meanwhile,the influence of dual dominant factors in the natural environment on cropland systems health is increasing.Furthermore,the MGWR model performed better in revealing the complex relationships between natural and social factors and changes in cropland systems health,demonstrating the significant spatial heterogeneity of the impacts of natural environment and human activities on cropland systems health.The re-search can provide scientific guidance for the sustainable development of TBSN and formulate more precise and effective cropland pro-tection policies.
文摘This review provides a comprehensive overview of recent advancements in aluminum-based conductor alloys engineered to achieve superior mechanical strength and thermal stability without sacrificing electrical conductivity.Particular emphasis is placed on the role of microalloying elements—particularly Sc and Zr-in promoting the formation of coherent nanoscale precipitates such as Al_(3)Zr,Al_(3)Sc,and core-shell Al_(3)(Sc,Zr)with metastable L1_(2)crystal structures.These precipitates contribute significantly to high-temperature performance by enabling precipitation strengthening and stabilizing grain boundaries.The review also explores the emerging role of other rare earth elements(REEs),such as erbium(Er),in accelerating precipitation kinetics and improving thermal stability by retarding coarsening.Additionally,recent advancements in thermomechanical processing strategies are examined,with a focus on scalable approaches to optimize the strength-conductivity balance.These approaches involve multi-step heat treatments and carefully controlled manufacturing sequences,particularly the combination of cold drawing and aging treatment to promote uniform and effective precipitation.This review offers valuable insights to guide the development of cost-effective,high-strength,heat-resistant aluminum alloys beyond conductor applications,particularly those strengthened through microalloying with Sc and Zr.
基金supported by the National Key R&D Program of China (Grant No.2022YFA1403201)the National Natural Science Foundation of China (Grant Nos.12125404,T2495231,123B2049,and 12204138)+9 种基金the Advanced MaterialsNational Science and Technology Major Project (Grant No.2024ZD0607000)the Natural Science Foundation of Jiangsu Province (Grant Nos.BK20233001 and BK20253009)the Jiangsu Funding Program for Excellent Postdoctoral Talent (Grant No.2024ZB002)the China Postdoctoral Science Foundation (Grant No.2025M773331)the Fundamental and Interdisciplinary Disciplines Breakthrough Plan of the Ministry of Education of Chinathe AI&AI for Science program of Nanjing UniversityArtificial Intelligence and Quantum physics (AIQ) program of Nanjing Universitythe Fundamental Research Funds for the Central Universitiesthe Natural Science Foundation of Nanjing University of Posts and Telecommunications(Grant Nos.NY224165,NY220038,and NY219087)the Hua Li Talents Program of Nanjing University of Posts and Telecommunications。
文摘We report a theoretical investigation into superconductivity within the MAXH_(6) quaternary hydride system using first-principles calculations,where M and A denote alkali and alkaline earth elements,respectively,and X represents transition metal elements.Systematic analysis of electronic band structures,phonon dispersions,and electron-phonon coupling reveals that substitution of MA binary metal combinations and X metal atoms can create favorable conditions for superconductivity.Mapping of superconducting critical temperatures,combined with dynamical stability analysis through phonon calculations,identifies ten superconducting candidates at ambient pressure.Among these,LiNaAgH_(6) exhibits nearly-free-electron behavior reminiscent of monovalent electron superconductors.It demonstrates exceptional superconducting properties with electron–phonon coupling λ=2.707,which yields a superconducting transition temperature T_(c) of 206.4 K using the Allen–Dynes formula.Its structural analogs MgNaPdH_(6),LiMgPdH_(6),LiMgAgH_(6),LiMgAuH_(6) all exhibit superconducting transition temperatures above 110 K.These findings advance our fundamental understanding of superconductivity in quaternary hydrides and provide guidance for rational design of new high-temperature superconducting materials.
基金supported by Natural Science Foundation of Heilongjiang Province of China(E2017030,ZD2017010)National Natural Science Foundation of China(51671063,51771060,51871069)+1 种基金Fundamental Research Funds for the Central Universities(HEUCFM181002)Foundation of State Key Laboratory of Rare Earth Resources Utilization(RERU2018017).
文摘Higher strength is always the goal pursued by researchers for the structural materials,especially for the lightweight magnesium(Mg)alloys which generally have relatively low strength at present.From this aspect,the present paper reviews the recent reports of a kind of Mg alloys,i.e.Mg-RE(RE:rare earths,mainly Gd or Y)casting and wrought alloys,which have been able to achieve high strength compared with common or commercial Mg alloys,from the viewpoint and content of the alloy system,alloying constitution,preparation process,tensile strength and each of the main strengthening mechanisms.This review of recent research and developments in high-strength Mg-RE alloys is beneficial for the further design of Mg alloys with higher strength as well as excellent comprehensive performance.
基金Project supported by the National Basic Research Program of China(2012CBA01202)the National Natural Science Foundation of China(51174184)
文摘The current recovery technique of Sc was complicated and the chemical consumption was high,This was due to the low content of Sc in resources and the difficulty of stripping.In this research,the isooctanol was added into the 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester(P507)extraction system to reduce the extraction and improve the stripping of Sc.The maximum stripping ratio of Sc from loaded organic phase by sulfuric acid can increase from 10%(without isooctanol)to 99%(with 15 vol%isooctanol).In the extraction test of the simulated red mud leaching liquor,the separation factors between Sc and Zr,Sc and Ti are 36 and 350,separately.At the same time,other metals are almost not extracted.The high selectivity and stripping of Sc suggest that the P507 with isooctanol extraction system can be applied in the practical Sc recovery process.
基金Project supported by Program of National Natural Science Foundation of China(51604128)China Postdoctoral Science Foundation(2017M620279,2018T110661)+3 种基金Key Projects of the Major Research and Development Program of Jiangxi Province(20171ACE50008)Qingqiang Excellent Young Talents,Jiangxi University of Science and Technology(JXUSTQJYX2018003)Key R&D Programs of Science and Technology Project of Ganzhou City([2017]179)Science and Technology Innovation Talents Program of Ganzhou City([2018] 50)
文摘In order to solve the problem of ammonia-nitrogen pollution in the enrichment process of the ionadsorption type rare earth ore,the technology of non-ammonia precipitation with magnesium oxide precipitant was carried out.It is determined that the rare earth precipitation efficiency is 99.6%and the purity of rare earth concentrates is only 85.89 wt%under the optimum precipitation conditions.And the contents of MgO,SO3 and Al2O3 in the rare earth concentrates are 5.12 wt%,6.77 wt%and 1.78 wt%,respectively.Furthermore,the thermo-decomposition process of precipitates was investigated by TGDSC,XRD and FI-IR.The thermal decomposition process consists of two stages:the dehydration of rare earth hydroxide and alkaline rare earth sulfate within 900℃and the thermal decomposition of RE2O2SO4 at 900-1300℃.Therefore,a high-temperature calcinations method for removing SO3 from precipitates is proposed.When the precipitates are calcined at 1300℃for 2 h,the rare earth concentrates with a purity of 92.03 wt%can be acquired.Moreover,the content of SO3 in the concentrate is only 0.46 wt%.In the MgO precipitation and high-temperature calcinations process,the raw material cost is low and the quality of rare earth concentrates is acceptable.It could have great significance for nonammonia enrichment of rare earth from the rare earth leaching liquor,and finally solve the problem of ammonia nitrogen in the extraction process of the ion-adsorption type rare earth ore within magnesium salt system.
基金We thank Yu He,Qingyang Hu,Jin Liu,Duckyoung Kim,and Li Zhang for sharing preliminary information.W.L.Mao acknowledges support from NSF Geophysics Grant No.EAR 1446969H.-k.Mao acknowledges supports from NSF Geochemistry Grant No.EAR-1447438+1 种基金NSF Geophysics Grant No.EAR-1722515This work was also partially supported by the National Natural Science Foundation of China Grant No.U1530402 and U1930401.
文摘Compelling evidence indicates that the solid Earth consists of two physicochemically distinct zones separated radially in the middle of the lower mantle at∼1800 km depth.The inner zone is governed by pressure-induced physics and chemistry dramatically different from the conventional behavior in the outer zone.These differences generate large physical and chemical potentials between the two zones that provide fundamental driving forces for triggering major events in Earth’s history.One of the main chemical carriers between the two zones isH_(2)Oin hydrous minerals that subducts into the inner zone,releases hydrogen,and leaves oxygen to create superoxides and form oxygen-rich piles at the core–mantle boundary,resulting in localized net oxygen gain in the inner zone.Accumulation of oxygen-rich piles at the base of the mantle could eventually reach a supercritical level that triggers eruptions,injecting materials that cause chemical mantle convection,superplumes,large igneous provinces,extreme climate changes,atmospheric oxygen fluctuations,and mass extinctions.Interdisciplinary research will be the key for advancing a unified theory of the four-dimensional Earth system.
基金Project supported by National Natural Science Foundation of China(50974042,51104040,51274060)the National Program on Key Basic Research Project of China(973 Program,2012CBA01205)+1 种基金the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(2012BAE01B00)the Scientific Research Special Foundation of Doctor Subject of Chinese Universities(20100042110008)
文摘Emulsification troubled normal extraction process of rare earths due to the existence of non-rare earth impurities, especially Si, Al and Fe. Against this background, the effect of emulsification caused by Si, Al and Fe on the La extraction with saponification P507 （2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester） in chloride medium was systematically investigated. A series of experiments were carried out to study the relationship of the extraction capacity of La and the concentration of impurities. ZPM-203 polarizing microscope was applied to investigate the morphology of emulsification, and the cation exchange extraction mechanism of Fe and Al as well as La was clarified by IR spectra. The results showed that a low concentration of Si in organic phase would aggravate the emulsification with Al, and the formation of ME （micro emulsion） and club-shaped polymer would result in emulsification in the extraction of mixtures of Si and Al, single Fe, respectively. Furthermore, the accumulation of impurity such as Si, Al and Fe in the organic phase would severely reduce the extraction capacity of La simultaneously.
基金Project supported bythe National Natural Science Foundation of China (30270744) and 863 Program(2002AA241121)
文摘After treated with low concentration of La^3 ＋ , the rate of producing active oxygen free radical, the relative permeability of cell membrane, the contents of bivalent iron ion in wheat seedling leaves under water stress were determined. The results show that in wheat seedling leaves, feasible concentrations of La^3 ＋ decreases the accumulation of active oxygen free radical, inhibits the increase of the relative permeability of cell membrane, reduces the content of peroxidation product MDA of membrane lipid, and prevents the plant cell producing more bivalent iron ion which can catalyzed the reaction of Haber-weiss and Fenton to produce more superoxide anion. In addition, purified plasma membrane was isolated by aqueous two-phase partitioning from wheat seedling leaves. The reduction rate of Fe（CN）6^3- by purified plasma membrane in La^3＋ -treated wheat seedling leaves is different from those in the absence of La^3＋ under water stress. The changing trend of the redox activity to La^3＋ is similar to that of the content of Fe^2＋ . The results reveal that extraneous La^3＋ can alleviate the damages of cell membrane caused by water stress via promoting the activity of redox system and the ability of eliminating ROS in wheat seedling leaves.
