This paper proposes a new distributed formation flight protocol for unmanned aerial vehicles(UAVs)to perform coordinated circular tracking around a set of circles on a target sphere.Different from the previous results...This paper proposes a new distributed formation flight protocol for unmanned aerial vehicles(UAVs)to perform coordinated circular tracking around a set of circles on a target sphere.Different from the previous results limited in bidirectional networks and disturbance-free motions,this paper handles the circular formation flight control problem with both directed network and spatiotemporal disturbance with the knowledge of its upper bound.Distinguishing from the design of a common Lyapunov fiunction for bidirectional cases,we separately design the control for the circular tracking subsystem and the formation keeping subsystem with the circular tracking error as input.Then the whole control system is regarded as a cascade connection of these two subsystems,which is proved to be stable by input-tostate stability(ISS)theory.For the purpose of encountering the external disturbance,the backstepping technology is introduced to design the control inputs of each UAV pointing to North and Down along the special sphere(say,the circular tracking control algorithm)with the help of the switching function.Meanwhile,the distributed linear consensus protocol integrated with anther switching anti-interference item is developed to construct the control input of each UAV pointing to east along the special sphere(say,the formation keeping control law)for formation keeping.The validity of the proposed control law is proved both in the rigorous theory and through numerical simulations.展开更多
The surface uplift of the Tibetan Plateau(TP)and its geomorphology evolution has triggered aridification of Asia's interior and drainage development at the eastern margin of the plateau.However,how the pre-Cenozoi...The surface uplift of the Tibetan Plateau(TP)and its geomorphology evolution has triggered aridification of Asia's interior and drainage development at the eastern margin of the plateau.However,how the pre-Cenozoic early growth histories of the TP impact the drainage system and climate is poorly constrained.The Late Mesozoic Lacustrine evaporite-bearing basins on the eastern margin of the TP record significant information on the uplift of the source terranes,source-to-sink system development and climate change.In this study,we presented detrital zircon U-Pb ages from the Upper Cretaceous Yunlong Formation in the Lanping Basin,as well as Hf isotopic,petrographic,direct statistical,and multidimensional scaling analyses,and use them to characterize the provenance and reconstruct the drainage system.All of the samples have five major age peaks at 200-290 Ma,400-490 Ma,750-1000 Ma,1750-1950 Ma,and 2400-2600 Ma with mostly negativeε_(Hf)(t)values(81%).We infer the sediments are primarily derived from recycled sediments of the Songpan-Garze terrane,and partly from the Sichuan Basin and the Southern Qiangtang terrane,as well as the exposed magmatic rocks of the Yidun Arc and SongpanGarze terrane.The provenance features of the contemporaneous sediments from the Sichuan,Xichang,Chuxiong,and Simao basins indicate a complex hierarchical drainage pattern on the eastern margin of the TP during the Late Cretaceous.The hierarchical drainage system exhibits a complete gradational cycle of lake-basin types from overfilled freshwater Sichuan Basin through balanced fill saline Xichang Basin and underfilled hypersaline Chuxiong,Lanping,Simao,and Khorat Plateau basins from proximal to distal.The early growth of the TP primarily controlled the drainage and lake-basin evolution by not only causing the uplift and exhumation of the source areas and providing large amounts of clastic material to the proximal sub-drainage areas but also intensifying the aridity and deposition of evaporites.展开更多
Vanadium in the black rocks has economic and environmental impacts.In sediments,it is broadly disseminated as a multivalent metal element mainly sensitive to redox settings.Globally in petroleum,it is considered an ab...Vanadium in the black rocks has economic and environmental impacts.In sediments,it is broadly disseminated as a multivalent metal element mainly sensitive to redox settings.Globally in petroleum,it is considered an abundant component.Vanadium is an essential tool to determine the relationship of the Earth with extra-terrestrial bodies.In the Yangtze region,the black rocks of the Early Cambrian Niutitang Formation are highly enriched in the concentration of V,Co,Ni and Mo.These sediments are comprised of a high total organic carbon content,and the average concentration of vanadium is over 240 ppm.Here we discuss the mechanisms and conditions that were responsible for the accumulation of vanadium in these black sediments in the Yangtze region.The oxygenated ocean water is favorable for the dissolved vanadate species Ⅴ(Ⅴ).Therefore,in oxic ocean-water,it can be reduced by organic matters or by H_(2)S to vanadyl ions Ⅴ(Ⅳ),which can facilely be adsorbed to the tiny particles and finally deposit into the sediments with the settling of the particles.The presence of V_(2)O_(3) in the Niutitang Formation indicates the isomorphism state of vanadium existence in the clay minerals.Clays and pyrite are the most favorable mineral for vanadium enrichment.However,it is suggested the quartz of non-biogenic origin might be unfavorable for vanadium enrichment.Vanadium is mainly derived from the diagenetic transformation of its precursor(porphyrin pigments and chlorophyll)from the organism.During the Early Cambrian period,the massive transgression in the sea level created a favorable environment for organisms to survive.Additionally,the hydrothermal activities brought massive nutrient supply in the form of vanadium and other metal elements from the deep Earth.These creatures consumed the vanadium-rich nutrients,which became a part of their bodies in the form of hard and soft parts.Later on,when these organisms died and were submerged in the sediments.After the diagenetic actions,this vanadium became a part of these black sediments along with organic carbon.Therefore,these black rocks in the Yangtze region are enriched in vanadium and organic carbon.It is suggested the various processes such as adsorption,complexation,and reductions are the main factors responsible for the precipitation of dissolved vanadium into the organically rich sediments.展开更多
This study is aimed to delineate the subsurface structural elements using geophysical techniques in the Haraza area of Pakistan.We investigated the Oghi and Battal thrust faults,sedimentary and metasedimentary wedge,a...This study is aimed to delineate the subsurface structural elements using geophysical techniques in the Haraza area of Pakistan.We investigated the Oghi and Battal thrust faults,sedimentary and metasedimentary wedge,and the absolute crustal thickness based on terrestrial gravity data.Unlike seismic survey relying on wave propagation,magnetic survey is based on both attraction and repulsion,and electrical and electromagnetics on induction.The attractive gravity field produces relatively simpler patterns of anomalies,like a series of highs and lows over regions with undulating basements and buried structures.A qualitative interpretation of gravity data reveals a good deal of information.During the collision of Indian and Eurasian Plates,compressional structures were developed in the Lesser Himalayas or northwest of the Hazara Kashmir Syntaxis.The study mainly focuses on the western limb of the Hazara Kashmir Syntaxis.The regional and local Bouguer anomalies were incorporated to delineate the regional structural units.The gravity model is computed through geophysical technique along with profile A-A'from Mansehra to the Battal area that demarcates the blind Oghi Thrust and emergent Battal Thrust.Tanol Formation of Precambrian age demarcates the Oghi Thrust near Kotli Pine while the Battal Thrust is demarcated within the Mansehra Granite of Cambrian to Ordovician age near Battal.Along with the Battal Thrust,fault gouge and breccias have been observed during the field studies.The total thickness of the sedimentary/metasedimentary wedge in the Mansehra and Battal areas was estimated to be 13.6 km and 14.2 km.In comparison,the total thickness of crust in the Mansehra and Battal areas was 51.6 km and 52.2 km,respectively.展开更多
The cultivation technology were standardized for improving the yield and quality,and the commodity value and the competitiveness of fruit market,and solving the bottleneck problem—fruit quality and yield that affect ...The cultivation technology were standardized for improving the yield and quality,and the commodity value and the competitiveness of fruit market,and solving the bottleneck problem—fruit quality and yield that affect the industrial development of rare and multi-purpose wild fruit Kadsura coccinea(Lem.)A.C.Smith.Through the investigation of K.coccinea production area and planting area,collection and analysis of fruit samples,it was found that in most planting area,the varieties of K.coccinea were mixed,with great differences in fruit quality and yield,which makes it impossible to realize large-scale planting.In view of these problems,a series of studies have been carried out and the technical regulations for standardized planting of rare and multi-purpose wild fruit K.coccinea were formulated.展开更多
The Niutitang Formation in the South China Block might be a source of hydrocarbon as it contains an enormous quantity of organic matter.Black rock of the Early Cambrian Niutitang Formation is widely distributed in the...The Niutitang Formation in the South China Block might be a source of hydrocarbon as it contains an enormous quantity of organic matter.Black rock of the Early Cambrian Niutitang Formation is widely distributed in the Yangtze region,but detailed geochemical understanding of it is still emerging.This research discusses the detailed geochemical characteristics of the Niutitang Formation to reconstruct the paleoenvironmental conditions,employing total organic carbon(TOC)content,major,trace,and rare earth element data.For this purpose,black rock specimens of the Niutitang Formation from two outcrop sections were utilized for geochemical characterization,and the results compared with another eight sections from the South China Block.The average total organic carbon in these sediments is significantly higher(5.80 wt.%).In the platform region,lower quantities of TOC indicate a poor potential to produce hydrocarbons.At the same time,significantly higher TOC is observed in the deep shelf and slope sediments,indicating a significant potential to produce hydrocarbons.The average Ce,Eu and Y anomalies from both Longbizui and Sancha sections studied are 0.74,0.86,1.77,1.07,and 1.19,1.30,respectively.The chemical index of alteration(CAI)throughout the Yangtze block is higher(averaging 71.32)than that of Post Archean Australian Shale(PAAS 69),indicating a moderately weathered source of the Niutitang Formation relative to PAAS.As the sediments are moderately weathered,this suggests these rocks might have been derived from felsic rocks,mainly granite-granodiorite.The normalization of REEs in the black rocks reveals a reduction of light REEs with increase in heavy REEs enrichment.Similarly,a positive Eu anomaly,negative Ce anomaly,and a moderate Y/Ho(34.61)are clues to a hybrid depositional mechanism associated with hydrothermal action and terrigenous input.These anomalies are also evidence of upwelling in the paleo-ocean and mixing of organic matter,which created anoxic bottom water during the deposition of the Niutitang Formation in the basin and upper oxic water conditions before deposition.The main controlling factors for the distribution of rare earth elements in these black rocks of the Niutitang Formation are pH,terrigenous input,source rock composition,tectonism,an upwelling mechanism,and hydrothermal activity.展开更多
Cellulose has a wide range of applications in many fields due to their naturally degradable and low-cost characteristics,but few studies can achieve cellulose-nanofibers by conventional electrospinning.Herein,we demon...Cellulose has a wide range of applications in many fields due to their naturally degradable and low-cost characteristics,but few studies can achieve cellulose-nanofibers by conventional electrospinning.Herein,we demonstrate that the freestanding cellulose-based carbon nanofibers are successfully obtained by a special design of electrospinning firstly,pre-oxidation and high-temperature carbonization(1600℃),which display a superior electrical conductivity of 31.2 S·cm^(-1)and larger specific surface area of 35.61 m^(2)·g^(-1)than that of the polyacrylonitrile-based carbon nanofibers(electrical conductivity of 18.5 S·cm^(-1),specific surface area of 12 m^(2)·g^(-1).The NiCo_(2)O_(4)nanoflake arrays are grown uniformly on the cellulose-based carbon nanofibers successfully by a facile one-step solvothermal and calcination method.The as-prepared cellulose-based carbon nanofibers/NiCo_(2)O_(4)nanoflake arrays are directly used as electrodes to achieve a high specific capacitance of 1010 F·g^(-1)at 1 A·g^(-1)and a good cycling stability with 90.84%capacitance retention after 3000 times at 10 A·g^(-1).Furthermore,the all-solid-state symmetric supercapacitors assembled from the cellulose-based carbon nanofibers/NiCo_(2)O_(4)deliver a high energy density of 62 W·h·kg(-1) at a power density of 1200 W·kg^(-1).Six all-solid-state symmetric supercapacitors in series can also power a‘DHU’logo consisted of 36 light emitting diodes,confirming that the cellulose-based carbon nanofiber is a promising carbon matrix material for energy storage devices.展开更多
Knowledge on the origin and mechanism of the large potash formation in the southeast Tethyan tectonic domain are still under debate,one of which mainly due to the controversial ages of the potash-bearing strata.Here w...Knowledge on the origin and mechanism of the large potash formation in the southeast Tethyan tectonic domain are still under debate,one of which mainly due to the controversial ages of the potash-bearing strata.Here we present a detailed detrital zircon U-Pb geochronologic-magnetostratigraphic study of the potash-bearing Mengyejing(MYJ)Formation(Fm)from the Simao Basin.948 paleomagnetic cores and 4 detrital zircon U-Pb samples were collected from a 932-m thick Jiangcheng section.Thermal demagnetization isolated 857 primary characteristic remnant magnetization(ChRM)directions,indicated by positive reversals and fold tests and petrologic examinations.Seven normal and seven reversed polarity zones were identified and correlated well with chrons C27r to C34n of the geomagnetic polarity timescale(GPTS2012),yielding the first known age sequence of>112 to~63 Ma for the MYJ Fm.The ages for the potash bearing strata in the Simao commenced~20 Ma earlier than those in the adjacent Khorat basins,opposite to the traditional viewpoint that the former would rather correspond to the middle and lower parts of the latter.Given the paleogeographic reconstruction of likely a pan-Simao-Khorat basin during the Cretaceous,~85 Ma would be another important potential period for future potash exploration in the Simao Basin.展开更多
Electric field is the energy foundation of the electrolysis process and the source of the multiphysical fields in a magnesium electrolysis cell. In this study, a three-dimensional numerical model was developed and use...Electric field is the energy foundation of the electrolysis process and the source of the multiphysical fields in a magnesium electrolysis cell. In this study, a three-dimensional numerical model was developed and used to calculate electric field at the steady state through the finite element analysis. Based on the simulation of the electric field, the operational and structural parameters, such as the current intensity, anode thickness, cathode thickness, and anode-cathode distance (ACD), were investigated to obtain the minimum cell voltage. The optimization is to obtain the minimum resistance voltage which has a significant effect on the energy consumption in the magnesium electrolysis process. The results indicate that the effect of the current intensity on the voltage could be ignored and the effect of the ACD is obvious. Moreover, there is a linear decrease between the voltage and the thicknesses of the anode and cathode; and the anodecathode working height also has a significant effect on the voltage.展开更多
A weak transverse static magnetic field(WTSMF,0–0.5 T)is applied to the directional solidification process of a DD3 Ni-based SX superalloy,aiming to tailor the microstructure and microsegregation of alloys.The mechan...A weak transverse static magnetic field(WTSMF,0–0.5 T)is applied to the directional solidification process of a DD3 Ni-based SX superalloy,aiming to tailor the microstructure and microsegregation of alloys.The mechanisms of microstructural refinement and microsegregation distribution caused by a WTSMF during directional solidification are discussed.It is shown that the primary dendrite arm spacing is rapidly reduced from 181 to 143μm,and the average size ofγ′phase is significantly refined from 0.85 to 0.25μm as the magnetic field increases from 0 to 0.5 T.At the same time,the volumefractions ofγ/γ′eutectic and the segregation coefficient are also gradually decreased.The 3D numerical simulations of the multiscale convection in liquid phase show that the modifications of the microstructure and microsegregation in DD3 are mainly attributed to the enhanced liquid flow caused by thermoelectric magnetic convection(TEMC)at dendrite/sample scale under the WTSMF.The maximum of the TEMC increases with increasing the magnetic field intensity.This work paves a simple way to optimize the microstructure and microsegregation in directionally solidified Ni-based SX superalloys without changing the processing parameters and composition.展开更多
Emerging evidence has highlighted the role of gut microbiome in human health.However,the integrative role of gut microbiome and microbial metabolites in acute myocardial infarction(AMI)remains unclear.The current stud...Emerging evidence has highlighted the role of gut microbiome in human health.However,the integrative role of gut microbiome and microbial metabolites in acute myocardial infarction(AMI)remains unclear.The current study profiles the microbial community through 16S rRNA gene sequencing and shotgun metagenomic sequencing and measures fecal short-chain fatty acids and circulating choline pathway metabolites among 117 new-onset AMI cases and 78 controls.Significant microbial alternations are observed in AMI patients compared with controls(P=0.001).The abundances of nine species(e.g.,Streptococcus salivarius and Klebsiella pneumoniae)are positively associated,and one species(Roseburia hominis)is inversely associated with AMI status and severity.A gut microbial score at disease onset is associated with the risk of major adverse cardiovascular events in 3.2 years(hazard ratio[95%CI]:2.01[1.04-4.24])in AMI patients.The molar proportions of fecal acetate and butyrate are higher,and the circulating levels of choline and carnitine are lower in AMI patients than in controls.In addition,disease classifiers show that AMI cases and controls have a more distinct pattern in taxonomical composition than in pathways or metabolites.Our findings suggest that microbial composition and functional potentials are associated with AMI status and severity.展开更多
基金supported in part by the National Natural Science Foundation of China(61673106)the Natural Science Foundation of Jiangsu Province(BK20171362)the Fundamental Research Funds for the Central Universities(2242019K40024)
文摘This paper proposes a new distributed formation flight protocol for unmanned aerial vehicles(UAVs)to perform coordinated circular tracking around a set of circles on a target sphere.Different from the previous results limited in bidirectional networks and disturbance-free motions,this paper handles the circular formation flight control problem with both directed network and spatiotemporal disturbance with the knowledge of its upper bound.Distinguishing from the design of a common Lyapunov fiunction for bidirectional cases,we separately design the control for the circular tracking subsystem and the formation keeping subsystem with the circular tracking error as input.Then the whole control system is regarded as a cascade connection of these two subsystems,which is proved to be stable by input-tostate stability(ISS)theory.For the purpose of encountering the external disturbance,the backstepping technology is introduced to design the control inputs of each UAV pointing to North and Down along the special sphere(say,the circular tracking control algorithm)with the help of the switching function.Meanwhile,the distributed linear consensus protocol integrated with anther switching anti-interference item is developed to construct the control input of each UAV pointing to east along the special sphere(say,the formation keeping control law)for formation keeping.The validity of the proposed control law is proved both in the rigorous theory and through numerical simulations.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41572067,91855104,41802111)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA 20170301)the National Key Project for Basic Research of China(Grant No.2011CB403007)。
文摘The surface uplift of the Tibetan Plateau(TP)and its geomorphology evolution has triggered aridification of Asia's interior and drainage development at the eastern margin of the plateau.However,how the pre-Cenozoic early growth histories of the TP impact the drainage system and climate is poorly constrained.The Late Mesozoic Lacustrine evaporite-bearing basins on the eastern margin of the TP record significant information on the uplift of the source terranes,source-to-sink system development and climate change.In this study,we presented detrital zircon U-Pb ages from the Upper Cretaceous Yunlong Formation in the Lanping Basin,as well as Hf isotopic,petrographic,direct statistical,and multidimensional scaling analyses,and use them to characterize the provenance and reconstruct the drainage system.All of the samples have five major age peaks at 200-290 Ma,400-490 Ma,750-1000 Ma,1750-1950 Ma,and 2400-2600 Ma with mostly negativeε_(Hf)(t)values(81%).We infer the sediments are primarily derived from recycled sediments of the Songpan-Garze terrane,and partly from the Sichuan Basin and the Southern Qiangtang terrane,as well as the exposed magmatic rocks of the Yidun Arc and SongpanGarze terrane.The provenance features of the contemporaneous sediments from the Sichuan,Xichang,Chuxiong,and Simao basins indicate a complex hierarchical drainage pattern on the eastern margin of the TP during the Late Cretaceous.The hierarchical drainage system exhibits a complete gradational cycle of lake-basin types from overfilled freshwater Sichuan Basin through balanced fill saline Xichang Basin and underfilled hypersaline Chuxiong,Lanping,Simao,and Khorat Plateau basins from proximal to distal.The early growth of the TP primarily controlled the drainage and lake-basin evolution by not only causing the uplift and exhumation of the source areas and providing large amounts of clastic material to the proximal sub-drainage areas but also intensifying the aridity and deposition of evaporites.
基金the National Natural Science Foundation(NNCF)of China for awarding us pecuniary aid with Grant Numbers 41572099,and 41872127 to accomplish this scientific research.
文摘Vanadium in the black rocks has economic and environmental impacts.In sediments,it is broadly disseminated as a multivalent metal element mainly sensitive to redox settings.Globally in petroleum,it is considered an abundant component.Vanadium is an essential tool to determine the relationship of the Earth with extra-terrestrial bodies.In the Yangtze region,the black rocks of the Early Cambrian Niutitang Formation are highly enriched in the concentration of V,Co,Ni and Mo.These sediments are comprised of a high total organic carbon content,and the average concentration of vanadium is over 240 ppm.Here we discuss the mechanisms and conditions that were responsible for the accumulation of vanadium in these black sediments in the Yangtze region.The oxygenated ocean water is favorable for the dissolved vanadate species Ⅴ(Ⅴ).Therefore,in oxic ocean-water,it can be reduced by organic matters or by H_(2)S to vanadyl ions Ⅴ(Ⅳ),which can facilely be adsorbed to the tiny particles and finally deposit into the sediments with the settling of the particles.The presence of V_(2)O_(3) in the Niutitang Formation indicates the isomorphism state of vanadium existence in the clay minerals.Clays and pyrite are the most favorable mineral for vanadium enrichment.However,it is suggested the quartz of non-biogenic origin might be unfavorable for vanadium enrichment.Vanadium is mainly derived from the diagenetic transformation of its precursor(porphyrin pigments and chlorophyll)from the organism.During the Early Cambrian period,the massive transgression in the sea level created a favorable environment for organisms to survive.Additionally,the hydrothermal activities brought massive nutrient supply in the form of vanadium and other metal elements from the deep Earth.These creatures consumed the vanadium-rich nutrients,which became a part of their bodies in the form of hard and soft parts.Later on,when these organisms died and were submerged in the sediments.After the diagenetic actions,this vanadium became a part of these black sediments along with organic carbon.Therefore,these black rocks in the Yangtze region are enriched in vanadium and organic carbon.It is suggested the various processes such as adsorption,complexation,and reductions are the main factors responsible for the precipitation of dissolved vanadium into the organically rich sediments.
文摘This study is aimed to delineate the subsurface structural elements using geophysical techniques in the Haraza area of Pakistan.We investigated the Oghi and Battal thrust faults,sedimentary and metasedimentary wedge,and the absolute crustal thickness based on terrestrial gravity data.Unlike seismic survey relying on wave propagation,magnetic survey is based on both attraction and repulsion,and electrical and electromagnetics on induction.The attractive gravity field produces relatively simpler patterns of anomalies,like a series of highs and lows over regions with undulating basements and buried structures.A qualitative interpretation of gravity data reveals a good deal of information.During the collision of Indian and Eurasian Plates,compressional structures were developed in the Lesser Himalayas or northwest of the Hazara Kashmir Syntaxis.The study mainly focuses on the western limb of the Hazara Kashmir Syntaxis.The regional and local Bouguer anomalies were incorporated to delineate the regional structural units.The gravity model is computed through geophysical technique along with profile A-A'from Mansehra to the Battal area that demarcates the blind Oghi Thrust and emergent Battal Thrust.Tanol Formation of Precambrian age demarcates the Oghi Thrust near Kotli Pine while the Battal Thrust is demarcated within the Mansehra Granite of Cambrian to Ordovician age near Battal.Along with the Battal Thrust,fault gouge and breccias have been observed during the field studies.The total thickness of the sedimentary/metasedimentary wedge in the Mansehra and Battal areas was estimated to be 13.6 km and 14.2 km.In comparison,the total thickness of crust in the Mansehra and Battal areas was 51.6 km and 52.2 km,respectively.
基金Key R&D projects in Guangxi Zhuang Autonomous Region(GK AB18221091)Scientific Research and Scientific Planning of Guilin,Guangxi(20160223-1).
文摘The cultivation technology were standardized for improving the yield and quality,and the commodity value and the competitiveness of fruit market,and solving the bottleneck problem—fruit quality and yield that affect the industrial development of rare and multi-purpose wild fruit Kadsura coccinea(Lem.)A.C.Smith.Through the investigation of K.coccinea production area and planting area,collection and analysis of fruit samples,it was found that in most planting area,the varieties of K.coccinea were mixed,with great differences in fruit quality and yield,which makes it impossible to realize large-scale planting.In view of these problems,a series of studies have been carried out and the technical regulations for standardized planting of rare and multi-purpose wild fruit K.coccinea were formulated.
基金supported by the National Natural Science Foundation of China(Nos.41572099 and 41872127).
文摘The Niutitang Formation in the South China Block might be a source of hydrocarbon as it contains an enormous quantity of organic matter.Black rock of the Early Cambrian Niutitang Formation is widely distributed in the Yangtze region,but detailed geochemical understanding of it is still emerging.This research discusses the detailed geochemical characteristics of the Niutitang Formation to reconstruct the paleoenvironmental conditions,employing total organic carbon(TOC)content,major,trace,and rare earth element data.For this purpose,black rock specimens of the Niutitang Formation from two outcrop sections were utilized for geochemical characterization,and the results compared with another eight sections from the South China Block.The average total organic carbon in these sediments is significantly higher(5.80 wt.%).In the platform region,lower quantities of TOC indicate a poor potential to produce hydrocarbons.At the same time,significantly higher TOC is observed in the deep shelf and slope sediments,indicating a significant potential to produce hydrocarbons.The average Ce,Eu and Y anomalies from both Longbizui and Sancha sections studied are 0.74,0.86,1.77,1.07,and 1.19,1.30,respectively.The chemical index of alteration(CAI)throughout the Yangtze block is higher(averaging 71.32)than that of Post Archean Australian Shale(PAAS 69),indicating a moderately weathered source of the Niutitang Formation relative to PAAS.As the sediments are moderately weathered,this suggests these rocks might have been derived from felsic rocks,mainly granite-granodiorite.The normalization of REEs in the black rocks reveals a reduction of light REEs with increase in heavy REEs enrichment.Similarly,a positive Eu anomaly,negative Ce anomaly,and a moderate Y/Ho(34.61)are clues to a hybrid depositional mechanism associated with hydrothermal action and terrigenous input.These anomalies are also evidence of upwelling in the paleo-ocean and mixing of organic matter,which created anoxic bottom water during the deposition of the Niutitang Formation in the basin and upper oxic water conditions before deposition.The main controlling factors for the distribution of rare earth elements in these black rocks of the Niutitang Formation are pH,terrigenous input,source rock composition,tectonism,an upwelling mechanism,and hydrothermal activity.
基金supported by Key Support Project of State Key Laboratory for Modification of Chemical Fibers and Polymer Materials(Grant No.21M1060212)Open Project of Shanghai Key Laboratory of Lightweight Structural Composite Materials(Grant No.2232019A4-02)+1 种基金National Natural Science Foundation of China(Grant No.51503086)the Fundamental Research Funds for the Central Universities and Graduate Student Innovation Fund of Donghua University(Grant No.CUSF-DH-D-2022013).
文摘Cellulose has a wide range of applications in many fields due to their naturally degradable and low-cost characteristics,but few studies can achieve cellulose-nanofibers by conventional electrospinning.Herein,we demonstrate that the freestanding cellulose-based carbon nanofibers are successfully obtained by a special design of electrospinning firstly,pre-oxidation and high-temperature carbonization(1600℃),which display a superior electrical conductivity of 31.2 S·cm^(-1)and larger specific surface area of 35.61 m^(2)·g^(-1)than that of the polyacrylonitrile-based carbon nanofibers(electrical conductivity of 18.5 S·cm^(-1),specific surface area of 12 m^(2)·g^(-1).The NiCo_(2)O_(4)nanoflake arrays are grown uniformly on the cellulose-based carbon nanofibers successfully by a facile one-step solvothermal and calcination method.The as-prepared cellulose-based carbon nanofibers/NiCo_(2)O_(4)nanoflake arrays are directly used as electrodes to achieve a high specific capacitance of 1010 F·g^(-1)at 1 A·g^(-1)and a good cycling stability with 90.84%capacitance retention after 3000 times at 10 A·g^(-1).Furthermore,the all-solid-state symmetric supercapacitors assembled from the cellulose-based carbon nanofibers/NiCo_(2)O_(4)deliver a high energy density of 62 W·h·kg(-1) at a power density of 1200 W·kg^(-1).Six all-solid-state symmetric supercapacitors in series can also power a‘DHU’logo consisted of 36 light emitting diodes,confirming that the cellulose-based carbon nanofiber is a promising carbon matrix material for energy storage devices.
基金supported by the National Basic Research Program of China(Grant Nos.2011CB403000,2017YFC0602803)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA20070201)+2 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0707)the National Natural Science Foundation of China(Grant Nos.41988101,41907263,41974080)the Funding of the Qingtan Scholar Talent Project of Zaozhuang University。
文摘Knowledge on the origin and mechanism of the large potash formation in the southeast Tethyan tectonic domain are still under debate,one of which mainly due to the controversial ages of the potash-bearing strata.Here we present a detailed detrital zircon U-Pb geochronologic-magnetostratigraphic study of the potash-bearing Mengyejing(MYJ)Formation(Fm)from the Simao Basin.948 paleomagnetic cores and 4 detrital zircon U-Pb samples were collected from a 932-m thick Jiangcheng section.Thermal demagnetization isolated 857 primary characteristic remnant magnetization(ChRM)directions,indicated by positive reversals and fold tests and petrologic examinations.Seven normal and seven reversed polarity zones were identified and correlated well with chrons C27r to C34n of the geomagnetic polarity timescale(GPTS2012),yielding the first known age sequence of>112 to~63 Ma for the MYJ Fm.The ages for the potash bearing strata in the Simao commenced~20 Ma earlier than those in the adjacent Khorat basins,opposite to the traditional viewpoint that the former would rather correspond to the middle and lower parts of the latter.Given the paleogeographic reconstruction of likely a pan-Simao-Khorat basin during the Cretaceous,~85 Ma would be another important potential period for future potash exploration in the Simao Basin.
基金Acknowledgements We thank the financial support provided by the National Natural Science Foundation of China (Grant Nos. 21206038 and 51504099), the Specialized Research Fund for the Doctoral Program of Higher Education (New Teachers) (Grant No. 20120074120014), and the Fundamental Research Funds for the Central Universities.
文摘Electric field is the energy foundation of the electrolysis process and the source of the multiphysical fields in a magnesium electrolysis cell. In this study, a three-dimensional numerical model was developed and used to calculate electric field at the steady state through the finite element analysis. Based on the simulation of the electric field, the operational and structural parameters, such as the current intensity, anode thickness, cathode thickness, and anode-cathode distance (ACD), were investigated to obtain the minimum cell voltage. The optimization is to obtain the minimum resistance voltage which has a significant effect on the energy consumption in the magnesium electrolysis process. The results indicate that the effect of the current intensity on the voltage could be ignored and the effect of the ACD is obvious. Moreover, there is a linear decrease between the voltage and the thicknesses of the anode and cathode; and the anodecathode working height also has a significant effect on the voltage.
基金financially supported by the National Natural Science Foundation of China(Nos.51690163,52130204,52174376,51822405)the Science and Technology Innovation Team Plan of Shaan Xi Province(No.2021TD-17)+3 种基金the Joint Research Funds of the Department of Science&Technology of Shaanxi Province and NPU(No.2020GXLH-Z-024)the Fundamental Research Funds for the Central Universities(No.D5000210902)the Key R&D Program of ShaanXi Province(No.2019ZDLGY 04-04)the Research Fund of the State Key Laboratory of Solidification Processing(NPU)(No.2019-QZ-02)。
文摘A weak transverse static magnetic field(WTSMF,0–0.5 T)is applied to the directional solidification process of a DD3 Ni-based SX superalloy,aiming to tailor the microstructure and microsegregation of alloys.The mechanisms of microstructural refinement and microsegregation distribution caused by a WTSMF during directional solidification are discussed.It is shown that the primary dendrite arm spacing is rapidly reduced from 181 to 143μm,and the average size ofγ′phase is significantly refined from 0.85 to 0.25μm as the magnetic field increases from 0 to 0.5 T.At the same time,the volumefractions ofγ/γ′eutectic and the segregation coefficient are also gradually decreased.The 3D numerical simulations of the multiscale convection in liquid phase show that the modifications of the microstructure and microsegregation in DD3 are mainly attributed to the enhanced liquid flow caused by thermoelectric magnetic convection(TEMC)at dendrite/sample scale under the WTSMF.The maximum of the TEMC increases with increasing the magnetic field intensity.This work paves a simple way to optimize the microstructure and microsegregation in directionally solidified Ni-based SX superalloys without changing the processing parameters and composition.
基金supported by the National Key R&D Program of China at the Ministry of Science and Technology of the People’s Republic of China(Grant No.2021YFA301003)the Clinical Research Plan of Shanghai Hospital Development Center at the Shanghai Hospital Development Center(Grant No.SHDC2020CR1007A)+2 种基金the Shanghai Municipal Science and Technology Major Project at the Science and Technology Commission of Shanghai Municipality(Grant No.2017SHZDZX01)the General Program at the National Natural Science Foundation of China(Grant No.81973032)supported by the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning。
文摘Emerging evidence has highlighted the role of gut microbiome in human health.However,the integrative role of gut microbiome and microbial metabolites in acute myocardial infarction(AMI)remains unclear.The current study profiles the microbial community through 16S rRNA gene sequencing and shotgun metagenomic sequencing and measures fecal short-chain fatty acids and circulating choline pathway metabolites among 117 new-onset AMI cases and 78 controls.Significant microbial alternations are observed in AMI patients compared with controls(P=0.001).The abundances of nine species(e.g.,Streptococcus salivarius and Klebsiella pneumoniae)are positively associated,and one species(Roseburia hominis)is inversely associated with AMI status and severity.A gut microbial score at disease onset is associated with the risk of major adverse cardiovascular events in 3.2 years(hazard ratio[95%CI]:2.01[1.04-4.24])in AMI patients.The molar proportions of fecal acetate and butyrate are higher,and the circulating levels of choline and carnitine are lower in AMI patients than in controls.In addition,disease classifiers show that AMI cases and controls have a more distinct pattern in taxonomical composition than in pathways or metabolites.Our findings suggest that microbial composition and functional potentials are associated with AMI status and severity.