In order to improve the energy output consistency of 3, 3’-diamino-4, 4’-azoxyfurazan(DAAF) in the new insensitive booster and the safety and efficiency in the preparation process, a continuous preparation system of...In order to improve the energy output consistency of 3, 3’-diamino-4, 4’-azoxyfurazan(DAAF) in the new insensitive booster and the safety and efficiency in the preparation process, a continuous preparation system of DAAF from synthesis to spherical coating was designed and established in this paper, which combined ultrasonic micromixing reaction with microdroplet globular template. In the rapid micromixing stage, the microfluidic mixing technology with ultrasonic was used to synergistically strengthen the uniform and rapid mass transfer mixing reaction between raw materials to ensure the uniformity of DAAF particle nucleation-growth, and to prepare high-quality DAAF crystals with uniform structure and morphology and concentrated particle size distribution. In the microdroplet globular template stage, the microfluidic droplet technology was used to form a droplet globular template with uniform size under the shear action of the continuous phase of the dispersed phase solution containing DAAF particles and binder. The size of the droplet template was controlled by adjusting the flow rate ratio between the continuous phase and the dispersed phase. In the droplet globular template, with the diffusion of the solvent in the dispersed phase droplets, the binder precipitates to coat the DAAF into a ball, forming a DAAF microsphere with high sphericity, narrow particle size distribution and good monodispersity. The problem of discontinuity and DAAF particle suspension in the process was solved, and the coating theory under this process was studied. DAAF was coated with different binder formulations of fluororubber(F2604), nitrocellulose(NC) and NC/glycidyl azide polymer(GAP), and the process verification and evaluation of the system were carried out. The balling effects of large, medium and small droplet templates under different binder formulations were studied. The scanning electron microscope(SEM) results show that the three droplet templates under the three binder formulations exhibit good balling effect and narrow particle size distribution. The DAAF microspheres were characterized by powder X-ray diffraction(XRD), differential scanning calorimetry(DSC), thermo-gravimetric(TG) and sensitivity analyzer. The results showed that the crystal structure of DAAF did not change during the process, and the prepared DAAF microspheres had lower decomposition temperature and lower mechanical sensitivity than raw DAAF. The results of detonation parameters show that the coating of DAAF by using the above three binder formulations will not greatly reduce the energy output of DAAF, and has comparable detonation performance to raw DAAF. This study proves an efficient and safe continuous system from synthesis to spherical coating modification of explosives, which provides a new way for the continuous, safe and efficient preparation of spherical explosives.展开更多
Objective In recent decades,China has implemented a series of policies to address air pollution.We aimed to assess the health effects of these policies on stroke burden attributable to ambient fine particulate matter(...Objective In recent decades,China has implemented a series of policies to address air pollution.We aimed to assess the health effects of these policies on stroke burden attributable to ambient fine particulate matter(PM_(2.5)).Methods Joinpoint regression was applied to explore the temporal tendency of stroke burden based on data from the Global Burden of Disease 2019 study.Results The age-standardized rates of disability-adjusted life year(DALY)for stroke attributable to ambient PM2.5 in China,increased dramatically during 1990-2012,subsequently decreased at an annual percentage change(APC)of-1.98[95% confidence interval(CI):-2.26,-1.71]during 2012-2019.For ischemic stroke(IS),the age-standardized DALY rates doubled from 1990 to 2014,and decreased at an APC of-0.83(95%CI:-1.33,-0.33)during 2014-2019.Intracerebral hemorrhage(ICH)showed a substantial increase in age-standardized DALY rates from 1990 to 2003,followed by declining trends,with APCs of-1.46(95%CI:-2.74,-0.16)during 2003-2007 and-3.33(95%CI:-3.61,-3.06)during 2011-2019,respectively.Conversely,the age-standardized DALY rates for subarachnoid hemorrhage(SAH)generally declined during 1990-2019.Conclusion Our results clarified the dynamic changes of the ambient PM_(2.5)-attributable stroke burden in China during 1990-2019,highlighting the health effects of air quality improvement policies.展开更多
The unmanned aerial vehicle(UAV)swarm plays an increasingly important role in the modern battlefield,and the UAV swarm operational test is a vital means to validate the combat effectiveness of the UAV swarm.Due to the...The unmanned aerial vehicle(UAV)swarm plays an increasingly important role in the modern battlefield,and the UAV swarm operational test is a vital means to validate the combat effectiveness of the UAV swarm.Due to the high cost and long duration of operational tests,it is essential to plan the test in advance.To solve the problem of planning UAV swarm operational test,this study considers the multi-stage feature of a UAV swarm mission,composed of launch,flight and combat stages,and proposes a method to find test plans that can maximize mission reliability.Therefore,a multi-stage mission reliability model for a UAV swarm is proposed to ensure successful implementation of the mission.A multi-objective integer optimization method that considers both mission reliability and cost is then formulated to obtain the optimal test plans.This study first constructs a mission reliability model for the UAV swarm in the combat stage.Then,the launch stage and flight stage are integrated to develop a complete PMS(Phased Mission Systems)reliability model.Finally,the Binary Decision Diagrams(BDD)and Multi Objective Quantum Particle Swarm Optimization(MOQPSO)methods are proposed to solve the model.The optimal plans considering both reliability and cost are obtained.The proposed model supports the planning of UAV swarm operational tests and represents a meaningful exploration of UAV swarm test planning.展开更多
Polymer bonded explosives(PBXs)have high energy density,excellent mechanical properties and better thermal stability.In this study,droplet microfluidic technology was used to successfully prepare HMX/TATB microspheres...Polymer bonded explosives(PBXs)have high energy density,excellent mechanical properties and better thermal stability.In this study,droplet microfluidic technology was used to successfully prepare HMX/TATB microspheres.The effects of different binder types and binder concentrations on the morphology of the microspheres were studied,and results proved that NC/GAP(1:4)provides particles a regular spherical morphology and good dispersion.Subsequently,the influence of the concentration of the dispersed phase and the flow rate of the continuous phase on the particle size distribution of the microspheres was fully studied.The microspheres had narrow particle size distribution and high spherical shape.Under optimized process conditions,HMX/TATB microspheres were prepared and compared with the physical mixtures.The X-ray diffraction,differential scanning calorimetry,flow properties,bulk density,and mechanical sensitivity of the samples were also studied.Results showed that the crystal form of the microspheres remains unchanged,and the binder maintains good compatibility with explosives.In addition,the fluidity,bulk density,real density and safety performance of the microspheres are remarkably better than the physical mixture.This study provides a new method for preparing PBX with narrow particle size distribution,high spherical shape,excellent dispersion and high bulk density.展开更多
Non-spherical particles exist widely in natural and industrial fluid systems and the motions of nonspherical particles are significantly different from that of spherical particles.In this paper,a simplified model of n...Non-spherical particles exist widely in natural and industrial fluid systems and the motions of nonspherical particles are significantly different from that of spherical particles.In this paper,a simplified model of non-spherical particles considering particle drag correction,lift,and rotation was established.Based on the Eulerian-Lagrangian simulation,the dispersion characteristics of spherical and nonspherical particles with different Stokes numbers in a high-speed turbulent jet were analyzed and compared considering the effect of particle rotation.The results show that,the differences in particle dispersion and radial velocity fluctuation between non-spherical particles and spherical particles in the jet are significant,especially when Stokes number is large.Moreover,the effects of different type of forces on the dispersion of non-spherical particles and spherical particles were compared in detail,which revealed that the change of the Magnus force caused by the increase in the angular velocity of non-spherical particles plays a dominant role in the differences of particle dispersion.展开更多
Energetic materials pose challenges in preparation and handling due to their contradictory properties of high-energy and low-sensitivity.The emergence of co-crystal explosives is a new opportunity to change this situa...Energetic materials pose challenges in preparation and handling due to their contradictory properties of high-energy and low-sensitivity.The emergence of co-crystal explosives is a new opportunity to change this situation.If the co-crystal explosive is coated into spherical particles with uniform particle size distribution,this contradiction can be further reduced.Therefore,binder-coated hexanitrohexaazaisowurtzitane/2,4,6-trinitrotoluene(CL-20/TNT)co-crystal microspheres were prepared by droplet microfluidic technology in this work.The coating effects of different binder formulations of nitrocellulose(NC)and NC/fluorine rubber(F2604)on the co-crystal spheres were studied.The scanning electron microscopy(SEM)results showed that the use of droplet microfluidic technology with the above binders can provide co-crystal microspheres with regular spherical morphology,uniform particle size distribution and good dispersion.X-ray diffraction(XRD),fourier-transform infrared(FT-IR),differential scanning calorimetry(DSC)and thermo-gravimetric(TG)methods were employed to compare the properties of the co-crystal microspheres,raw material and pure co-crystal.The formation of CL-20/TNT co-crystal in the microspheres was confirmed,and the co-crystal microspheres exhibited better thermal stability than the raw material and pure co-crystal.In addition,the mechanical sensitivity and combustion performance of the co-crystal microspheres were further studied.The results showed that the co-crystal microspheres were more insensitive than CL-20 and pure co-crystal,and displayed excellent self-sustained combustion performance and theoretical detonation performance.This study provides a new method for the fast,simple and one-step preparation of CL-20/TNT co-crystal microspheres,with binder coating,uniform particle size distribution,and excellent performance level.展开更多
Here,we analyze the characteristics and the formation mechanisms of low-level jets(LLJs)in the middle reaches of the Yangtze River during the 2010 mei-yu season using Wuhan station radiosonde data and the fifth genera...Here,we analyze the characteristics and the formation mechanisms of low-level jets(LLJs)in the middle reaches of the Yangtze River during the 2010 mei-yu season using Wuhan station radiosonde data and the fifth generation of the European Centre for Medium-Range Weather Forecasts(ERA5)reanalysis dataset.Our results show that the vertical structure of LLJs is characterized by a predominance of boundary layer jets(BLJs)concentrated at heights of 900-1200 m.The BLJs occur most frequently at 2300 LST(LST=UTC+8 hours)but are strongest at 0200 LST,with composite wind velocities>14 m s^(-1).Synoptic-system-related LLJs(SLLJs)occur most frequently at 0800 LST but are strongest at 1100LST,with composite wind velocities>12 m s^(-1).Both BLJs and SLLJs are characterized by a southwesterly wind direction,although the wind direction of SLLJs is more westerly,and northeasterly SLLJs occur more frequently than northeasterly BLJs.When Wuhan is south of the mei-yu front,the westward extension of the northwest Pacific subtropical high intensifies,and the low-pressure system in the eastern Tibetan Plateau strengthens,favoring the formation of LLJs,which are closely related to precipitation.The wind speeds on rainstorm days are greater than those on LLJ days.Our analysis of four typical heavy precipitation events shows the presence of LLJs at the center of the precipitation and on its southern side before the onset of heavy precipitation.BLJs were shown to develop earlier than SLLJs.展开更多
Post-transplant diabetes mellitus(PTDM)increases the risk of graft failure and death in liver transplant(LT)recipients.Experimental studies have indicated that enteric dysbiosis mediated by immunosuppressive tacrolimu...Post-transplant diabetes mellitus(PTDM)increases the risk of graft failure and death in liver transplant(LT)recipients.Experimental studies have indicated that enteric dysbiosis mediated by immunosuppressive tacrolimus(TAC)could contribute to glucose disorders,but no data on human recipients with PTDM have been reported.Here,by combining high-throughput shotgun metagenomics sequencing and metabolomics profiling,we characterized the intestinal microbiome(IM)in LT recipient cohort with or without PTDM and deciphered the potential relationship among IM,TAC dosage,and diabetes.By comparing with both non-PTDM and classical type 2 diabetes mellitus(T2DM),we identified microbial signatures of PTDM,which was characterized by the enriched Proteobacteria and decreased Bacteroidetes.Additionally,the altered microbes,as well as the microbial metabolomics,correlated with the dosage of TAC.Specifically,the levels of beneficial microbes associated with PTDM were lowered in recipients with the high TAC trough concentrations(>5 ng·mL^(-1))than those with low ones(<5 ng·mL^(-1)),which was accompanied by reduced faecal metabolites involved in the biosynthesis of a-linolenic acid and arachidonic acid-lowering factors of developing T2DM.Moreover,these microbial signatures linked with the extent of glucose disorders in LT recipients.In summary,the faecal microbiome and metabolome differed between PTDM and non-PTDM patients,which were linked with TAC dosage.This study was the first to explore taxonomic alterations and bacterial gene functions to better understand the contribution of the IM to PTDM.展开更多
The connected autonomous vehicle is considered an effective way to improve transport safety and efficiency.To overcome the limited sensing and computing capabilities of individual vehicles,we design a digital twin ass...The connected autonomous vehicle is considered an effective way to improve transport safety and efficiency.To overcome the limited sensing and computing capabilities of individual vehicles,we design a digital twin assisted decision-making framework for Internet of Vehicles,by leveraging the integration of communication,sensing and computing.In this framework,the digital twin entities residing on edge can effectively communicate and cooperate with each other to plan sub-targets for their respective vehicles,while the vehicles only need to achieve the sub-targets by generating a sequence of atomic actions.Furthermore,we propose a hierarchical multiagent reinforcement learning approach to implement the framework,which can be trained in an end-to-end way.In the proposed approach,the communication interval of digital twin entities could adapt to timevarying environment.Extensive experiments on driving decision-making have been performed in traffic junction scenarios of different difficulties.The experimental results show that the proposed approach can largely improve collaboration efficiency while reducing communication overhead.展开更多
In this study,an acid-induced assembly strategy for a rutile TiO2 photocatalyst was proposed on the basis of the treatment of lamellar protonated titanate with a concentrated HNO3 solution.Nitrate groups were successf...In this study,an acid-induced assembly strategy for a rutile TiO2 photocatalyst was proposed on the basis of the treatment of lamellar protonated titanate with a concentrated HNO3 solution.Nitrate groups were successfully grafted onto a TiO2 surface and induced the assembly of rutile TiO2 nanorods into uniform spindle-like nanobundles.The resulting TiO2 product achieved a photocatalytic hydrogen evolution rate of 402.4μmol h^?1,which is 3.1 times higher than that of Degussa P25-TiO2.It was demonstrated that nitrate group grafting caused the rutile TiO2 surface to become negatively charged,which is favorable for trapping positive protons and improving charge carrier separation,thereby enhancing photocatalytic hydrogen production.Additionally,surface charges were crucial to structural stability based on electrostatic repulsion.This study not only developed a facile surface modification strategy for fabricating efficient H2 production photocatalysts but also identified an influence mechanism of inorganic acids different from that reported in the literature.展开更多
Photocatalytic conversion of“greenhouse gas”CO2is considered to be one of the most effective ways to alleviate current energy and environmental problems without additional energy consumption and pollutant emission.T...Photocatalytic conversion of“greenhouse gas”CO2is considered to be one of the most effective ways to alleviate current energy and environmental problems without additional energy consumption and pollutant emission.The performance of many traditional semiconductor photocatalysts is not efficient enough to satisfy the requirements of practical applications because of their limited specific surface area and low CO2adsorption capacity.Therefore,the exploration of photocatalysts with high CO2uptake is significant in the field of CO2conversion.Recently the porous materials appeared to be a kind of superior candidate for enriching the CO2molecules on the surface of photocatalysts for catalytic conversion.This paper first summarizes the advances in the development of nanoporous adsorbents for CO2capture.Three main classes of porous materials are considered:inorganic porous materials,metal organic frameworks,and microporous organic polymers.Based on systematic research on CO2uptake,we then highlight the recent progress in these porous‐material‐based photocatalysts for CO2conversion.Benefiting from the improved CO2uptake capacity,the porous‐material‐based photocatalysts exhibited remarkably enhanced efficiency in the reduction of CO2to chemical fuels,such as CO,CH4,and CH3OH.Based on reported recent achievements,we predict a trend of development in multifunctional materials with both high adsorption capability and photocatalytic performance for CO2utilization.展开更多
Electrochemical catalysts for oxygen evolution reaction are a critical component for many renewable energy applications. To improve their catalytic kinetics and mass activity are essential for sustainable industrial a...Electrochemical catalysts for oxygen evolution reaction are a critical component for many renewable energy applications. To improve their catalytic kinetics and mass activity are essential for sustainable industrial applications. Here, we report a rare-earth metal-based oxide electrocatalyst comprised of ultrathin amorphous La2O3 nanosheets hybridized with uniform La2O3 nanoparticles(La2O3@NP-NS). Significantly improved OER performance is observed from the nanosheets with a nanometer-scale thickness. The as-synthesized 2.27-nm La2O3@NP-NS exhibits excellent catalytic kinetics with an overpotential of 310 mV at 10 m A cm^-2, a small Tafel slope of 43.1 mV dec^-1, and electrochemical impedance of 38 Ω. More importantly, due to the ultrasmall thickness, its mass activity, and turnover frequency reach as high as 6666.7 A g^-1 and 5.79 s^-1, respectively, at an overpotential of 310 mV. Such a high mass activity is more than three orders of magnitude higher than benchmark OER electrocatalysts, such as IrO2 and RuO2. This work presents a sustainable approach toward the development of highly e cient electrocatalysts with largely reduced mass loading of precious elements.展开更多
Tailoring valence electron delocalization of transition metal center is of importance to achieve highly-active electrocatalysts for oxygen evolution reaction(OER).Herein,we demonstrate a“poor sulfur”route to synthes...Tailoring valence electron delocalization of transition metal center is of importance to achieve highly-active electrocatalysts for oxygen evolution reaction(OER).Herein,we demonstrate a“poor sulfur”route to synthesize surface electron-deficient Co_(9)S_(8) nanoarrays,where the binding energy(BE)of Co metal center is considerably higher than all reported Co_(9)S_(8)-based electrocatalysts.The resulting Co_(9)S_(8) electrocatalysts only require the overpotentials(h)of 265 and 326 mV at 10 and 100 mA cm^(-2) with a low Tafel slope of 56 mV dec^-(1) and a 60 hlasting stability in alkaline media.The OER kinetics are greatly expedited with a low reaction activation energy of 27.9 kJ mol^-(1) as well as abundant OOH*key intermediates(24%),thus exhibiting excellent catalytic performances.The surface electron-deficient engineering gives an available strategy to improve the catalytic activity of other advanced non-noble electrocatalysts.展开更多
The Harlem River, a 9.3-mile channel that flows from the Hudson River to the East River, has experienced decades of industrial abuse and remains gritty and industrial. During heavy rains, the pipes discharge raw sewag...The Harlem River, a 9.3-mile channel that flows from the Hudson River to the East River, has experienced decades of industrial abuse and remains gritty and industrial. During heavy rains, the pipes discharge raw sewage into the river through combined sewer overflows (CSOs) that can contain bacteria and cause illness. Water samples were collected from CSO discharge point and several adjacent sites along the river in the Bronx side close to River Park Towers at Richman Plaza and Manhattan side at Wards Island. Nutrients, bacteria, polychlorinated biphenyls (PCBs), and fish consumption safety have been analyzed. Results showed that phosphorus, ammonia concentration as well as fecal coliform, E.Coli, enterococcus levels increased significantly during heavy rainstorms. Ammonia concentration was up to 2.725 mg/L during tropical storm Arthur on July 2, 2014 and rainstorm in May 2013, and soluble reactive phosphorus (SRP) or orthophosphate was up to 0.197 mg/L during heavy thunderstorm in April 2011;both nutrients were exceeded EPA regulation for ammonia (0.23 mg/L) and phosphate (0.033 mg/L) for New York City (NYC) waters. The colonies of fecal coliform were more than 5 million MPN/100ml (most probable number per 100 ml) during tropical storm Arthur in July 2014 and heavy rainstorm in April 2014, and fecal coliform was more than 10,000 MPN/100ml during storm in July and November 2013;E.Coli reached more than 5000 MPN/100ml during tropical storm Arthur and storm in May 2013;enterococcus reached more than 10,000 MPN/100ml during tropical storm Arthur and heavy rainstorm in April 2014. These bacteria (pathogen) levels in the Harlem River were significantly higher than EPA standards (fecal coliform: 200 MPN/100ml, E.Coli: 126 MPN/100ml, enterococcus: 104 MPN/100ml), especially during rainstorm/tropical storm. Of particular significance, nutrients and bacteria were analyzed before and after Hurricane Sandy devastated NYC in late October 2012;results determined that bacteria and ammonia concentrations increased after this monumental storm, elucidating the environmental impact of large storm events. PCB 11 (3,3’-dichlorobiphenyl, C12H8Cl2), the high molecular weight (MW), an indicator of raw sewer and storm water runoff in the NYC harbor waters, is the major polychlorinated biphenyls (PCBs) in the Harlem River. PCBs are carcinogenic, which could bioaccumulate via food chain from fish and seafood, endangering public health. Oyster farming has been used to purify water and improve water quality in the river. CSOs and storm water runoff have degraded water quality and been threatening environmental ecosystem and public health. This research will help local communities understand CSO impact on nutrients, bacteria, PCBs contamination and fish consumption safety, and make contributions on CSOs reduction as well as improve water quality and environmental ecosystem in the Harlem River.展开更多
基金National Natural Science Foundation of China(Grant No.22005275)to provide fund for conducting experiments.
文摘In order to improve the energy output consistency of 3, 3’-diamino-4, 4’-azoxyfurazan(DAAF) in the new insensitive booster and the safety and efficiency in the preparation process, a continuous preparation system of DAAF from synthesis to spherical coating was designed and established in this paper, which combined ultrasonic micromixing reaction with microdroplet globular template. In the rapid micromixing stage, the microfluidic mixing technology with ultrasonic was used to synergistically strengthen the uniform and rapid mass transfer mixing reaction between raw materials to ensure the uniformity of DAAF particle nucleation-growth, and to prepare high-quality DAAF crystals with uniform structure and morphology and concentrated particle size distribution. In the microdroplet globular template stage, the microfluidic droplet technology was used to form a droplet globular template with uniform size under the shear action of the continuous phase of the dispersed phase solution containing DAAF particles and binder. The size of the droplet template was controlled by adjusting the flow rate ratio between the continuous phase and the dispersed phase. In the droplet globular template, with the diffusion of the solvent in the dispersed phase droplets, the binder precipitates to coat the DAAF into a ball, forming a DAAF microsphere with high sphericity, narrow particle size distribution and good monodispersity. The problem of discontinuity and DAAF particle suspension in the process was solved, and the coating theory under this process was studied. DAAF was coated with different binder formulations of fluororubber(F2604), nitrocellulose(NC) and NC/glycidyl azide polymer(GAP), and the process verification and evaluation of the system were carried out. The balling effects of large, medium and small droplet templates under different binder formulations were studied. The scanning electron microscope(SEM) results show that the three droplet templates under the three binder formulations exhibit good balling effect and narrow particle size distribution. The DAAF microspheres were characterized by powder X-ray diffraction(XRD), differential scanning calorimetry(DSC), thermo-gravimetric(TG) and sensitivity analyzer. The results showed that the crystal structure of DAAF did not change during the process, and the prepared DAAF microspheres had lower decomposition temperature and lower mechanical sensitivity than raw DAAF. The results of detonation parameters show that the coating of DAAF by using the above three binder formulations will not greatly reduce the energy output of DAAF, and has comparable detonation performance to raw DAAF. This study proves an efficient and safe continuous system from synthesis to spherical coating modification of explosives, which provides a new way for the continuous, safe and efficient preparation of spherical explosives.
基金supported by National Key Research and Development Program of China(2018YFE0115300,2022YFC3600800,2017YFC0211706)Chinese Academy of Medical Sciences(CAMS)Innovation Fund for Medical Sciences(2021-I2M-1-010)+3 种基金National Natural Science Foundation of China(82073658,82070473)National High Level Hospital Clinical Research Funding(2022-GSP-GG-1,2022-GSP-GG-2)Research Unit of Prospective Cohort of Cardiovascular Diseases and Cancers,CAMS(2019RU038)National Clinical Research Center for Cardiovascular Diseases,Fuwai Hospital,CAMS(NCRC2020006)。
文摘Objective In recent decades,China has implemented a series of policies to address air pollution.We aimed to assess the health effects of these policies on stroke burden attributable to ambient fine particulate matter(PM_(2.5)).Methods Joinpoint regression was applied to explore the temporal tendency of stroke burden based on data from the Global Burden of Disease 2019 study.Results The age-standardized rates of disability-adjusted life year(DALY)for stroke attributable to ambient PM2.5 in China,increased dramatically during 1990-2012,subsequently decreased at an annual percentage change(APC)of-1.98[95% confidence interval(CI):-2.26,-1.71]during 2012-2019.For ischemic stroke(IS),the age-standardized DALY rates doubled from 1990 to 2014,and decreased at an APC of-0.83(95%CI:-1.33,-0.33)during 2014-2019.Intracerebral hemorrhage(ICH)showed a substantial increase in age-standardized DALY rates from 1990 to 2003,followed by declining trends,with APCs of-1.46(95%CI:-2.74,-0.16)during 2003-2007 and-3.33(95%CI:-3.61,-3.06)during 2011-2019,respectively.Conversely,the age-standardized DALY rates for subarachnoid hemorrhage(SAH)generally declined during 1990-2019.Conclusion Our results clarified the dynamic changes of the ambient PM_(2.5)-attributable stroke burden in China during 1990-2019,highlighting the health effects of air quality improvement policies.
基金supported by the National Natural Science Foundation of China(with Granted Number 72271239,grant recipient P.J.)Research on the Design Method of Reliability Qualification Test for Complex Equipment Based on Multi-Source Information Fusion.https://www.nsfc.gov.cn/.
文摘The unmanned aerial vehicle(UAV)swarm plays an increasingly important role in the modern battlefield,and the UAV swarm operational test is a vital means to validate the combat effectiveness of the UAV swarm.Due to the high cost and long duration of operational tests,it is essential to plan the test in advance.To solve the problem of planning UAV swarm operational test,this study considers the multi-stage feature of a UAV swarm mission,composed of launch,flight and combat stages,and proposes a method to find test plans that can maximize mission reliability.Therefore,a multi-stage mission reliability model for a UAV swarm is proposed to ensure successful implementation of the mission.A multi-objective integer optimization method that considers both mission reliability and cost is then formulated to obtain the optimal test plans.This study first constructs a mission reliability model for the UAV swarm in the combat stage.Then,the launch stage and flight stage are integrated to develop a complete PMS(Phased Mission Systems)reliability model.Finally,the Binary Decision Diagrams(BDD)and Multi Objective Quantum Particle Swarm Optimization(MOQPSO)methods are proposed to solve the model.The optimal plans considering both reliability and cost are obtained.The proposed model supports the planning of UAV swarm operational tests and represents a meaningful exploration of UAV swarm test planning.
基金supported by the National Natural Science Foundation of China(No.22005275)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(STIP,No.2019L0584)the Advantage Disciplines Climbing Plan of Shanxi Province.
文摘Polymer bonded explosives(PBXs)have high energy density,excellent mechanical properties and better thermal stability.In this study,droplet microfluidic technology was used to successfully prepare HMX/TATB microspheres.The effects of different binder types and binder concentrations on the morphology of the microspheres were studied,and results proved that NC/GAP(1:4)provides particles a regular spherical morphology and good dispersion.Subsequently,the influence of the concentration of the dispersed phase and the flow rate of the continuous phase on the particle size distribution of the microspheres was fully studied.The microspheres had narrow particle size distribution and high spherical shape.Under optimized process conditions,HMX/TATB microspheres were prepared and compared with the physical mixtures.The X-ray diffraction,differential scanning calorimetry,flow properties,bulk density,and mechanical sensitivity of the samples were also studied.Results showed that the crystal form of the microspheres remains unchanged,and the binder maintains good compatibility with explosives.In addition,the fluidity,bulk density,real density and safety performance of the microspheres are remarkably better than the physical mixture.This study provides a new method for preparing PBX with narrow particle size distribution,high spherical shape,excellent dispersion and high bulk density.
基金supported by National Science and Technology Major Project of China(2019-I-0022-0021)Seed fund of Shanxi Research Institute for Clean Energy,Tsinghua Universitythe National Natural Science Foundation of China(51761125011)。
文摘Non-spherical particles exist widely in natural and industrial fluid systems and the motions of nonspherical particles are significantly different from that of spherical particles.In this paper,a simplified model of non-spherical particles considering particle drag correction,lift,and rotation was established.Based on the Eulerian-Lagrangian simulation,the dispersion characteristics of spherical and nonspherical particles with different Stokes numbers in a high-speed turbulent jet were analyzed and compared considering the effect of particle rotation.The results show that,the differences in particle dispersion and radial velocity fluctuation between non-spherical particles and spherical particles in the jet are significant,especially when Stokes number is large.Moreover,the effects of different type of forces on the dispersion of non-spherical particles and spherical particles were compared in detail,which revealed that the change of the Magnus force caused by the increase in the angular velocity of non-spherical particles plays a dominant role in the differences of particle dispersion.
基金National Natural Science Foundation of China(Grant No.22005275)to provide fund for conducting experiments。
文摘Energetic materials pose challenges in preparation and handling due to their contradictory properties of high-energy and low-sensitivity.The emergence of co-crystal explosives is a new opportunity to change this situation.If the co-crystal explosive is coated into spherical particles with uniform particle size distribution,this contradiction can be further reduced.Therefore,binder-coated hexanitrohexaazaisowurtzitane/2,4,6-trinitrotoluene(CL-20/TNT)co-crystal microspheres were prepared by droplet microfluidic technology in this work.The coating effects of different binder formulations of nitrocellulose(NC)and NC/fluorine rubber(F2604)on the co-crystal spheres were studied.The scanning electron microscopy(SEM)results showed that the use of droplet microfluidic technology with the above binders can provide co-crystal microspheres with regular spherical morphology,uniform particle size distribution and good dispersion.X-ray diffraction(XRD),fourier-transform infrared(FT-IR),differential scanning calorimetry(DSC)and thermo-gravimetric(TG)methods were employed to compare the properties of the co-crystal microspheres,raw material and pure co-crystal.The formation of CL-20/TNT co-crystal in the microspheres was confirmed,and the co-crystal microspheres exhibited better thermal stability than the raw material and pure co-crystal.In addition,the mechanical sensitivity and combustion performance of the co-crystal microspheres were further studied.The results showed that the co-crystal microspheres were more insensitive than CL-20 and pure co-crystal,and displayed excellent self-sustained combustion performance and theoretical detonation performance.This study provides a new method for the fast,simple and one-step preparation of CL-20/TNT co-crystal microspheres,with binder coating,uniform particle size distribution,and excellent performance level.
基金supported by the National Natural Science Foundation of China(Grant Nos.42230612,41620104009,41705019,42075186,and 41975058)the Projects of the S&T Development Foundation of the Hubei Meteorological Bureau(Grants No.2021Q04 and 2020Y04)。
文摘Here,we analyze the characteristics and the formation mechanisms of low-level jets(LLJs)in the middle reaches of the Yangtze River during the 2010 mei-yu season using Wuhan station radiosonde data and the fifth generation of the European Centre for Medium-Range Weather Forecasts(ERA5)reanalysis dataset.Our results show that the vertical structure of LLJs is characterized by a predominance of boundary layer jets(BLJs)concentrated at heights of 900-1200 m.The BLJs occur most frequently at 2300 LST(LST=UTC+8 hours)but are strongest at 0200 LST,with composite wind velocities>14 m s^(-1).Synoptic-system-related LLJs(SLLJs)occur most frequently at 0800 LST but are strongest at 1100LST,with composite wind velocities>12 m s^(-1).Both BLJs and SLLJs are characterized by a southwesterly wind direction,although the wind direction of SLLJs is more westerly,and northeasterly SLLJs occur more frequently than northeasterly BLJs.When Wuhan is south of the mei-yu front,the westward extension of the northwest Pacific subtropical high intensifies,and the low-pressure system in the eastern Tibetan Plateau strengthens,favoring the formation of LLJs,which are closely related to precipitation.The wind speeds on rainstorm days are greater than those on LLJ days.Our analysis of four typical heavy precipitation events shows the presence of LLJs at the center of the precipitation and on its southern side before the onset of heavy precipitation.BLJs were shown to develop earlier than SLLJs.
基金supported by the National Natural Science Foundation of China(82170668,82171757,and 82241215)the National Key Research and Development Program of China(2021YFA1301001)+2 种基金the Sino-German Center for Research Promotion(GZ1546)the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences(2019-I2M-5-045)the Research Project of Jinan Microecological Biomedicine Shandong Laboratory(JNL-2022040C and JNL-2023006C)。
文摘Post-transplant diabetes mellitus(PTDM)increases the risk of graft failure and death in liver transplant(LT)recipients.Experimental studies have indicated that enteric dysbiosis mediated by immunosuppressive tacrolimus(TAC)could contribute to glucose disorders,but no data on human recipients with PTDM have been reported.Here,by combining high-throughput shotgun metagenomics sequencing and metabolomics profiling,we characterized the intestinal microbiome(IM)in LT recipient cohort with or without PTDM and deciphered the potential relationship among IM,TAC dosage,and diabetes.By comparing with both non-PTDM and classical type 2 diabetes mellitus(T2DM),we identified microbial signatures of PTDM,which was characterized by the enriched Proteobacteria and decreased Bacteroidetes.Additionally,the altered microbes,as well as the microbial metabolomics,correlated with the dosage of TAC.Specifically,the levels of beneficial microbes associated with PTDM were lowered in recipients with the high TAC trough concentrations(>5 ng·mL^(-1))than those with low ones(<5 ng·mL^(-1)),which was accompanied by reduced faecal metabolites involved in the biosynthesis of a-linolenic acid and arachidonic acid-lowering factors of developing T2DM.Moreover,these microbial signatures linked with the extent of glucose disorders in LT recipients.In summary,the faecal microbiome and metabolome differed between PTDM and non-PTDM patients,which were linked with TAC dosage.This study was the first to explore taxonomic alterations and bacterial gene functions to better understand the contribution of the IM to PTDM.
基金supported in part by the Natural Science Foundation of China under Grant 62001054,Grant 62272053 and Grant 61901191in part by the Natural Science Foundation of Shandong Province of China under Grant ZR2020LZH005in part by the Fundamental Research Funds for the Central Universities。
文摘The connected autonomous vehicle is considered an effective way to improve transport safety and efficiency.To overcome the limited sensing and computing capabilities of individual vehicles,we design a digital twin assisted decision-making framework for Internet of Vehicles,by leveraging the integration of communication,sensing and computing.In this framework,the digital twin entities residing on edge can effectively communicate and cooperate with each other to plan sub-targets for their respective vehicles,while the vehicles only need to achieve the sub-targets by generating a sequence of atomic actions.Furthermore,we propose a hierarchical multiagent reinforcement learning approach to implement the framework,which can be trained in an end-to-end way.In the proposed approach,the communication interval of digital twin entities could adapt to timevarying environment.Extensive experiments on driving decision-making have been performed in traffic junction scenarios of different difficulties.The experimental results show that the proposed approach can largely improve collaboration efficiency while reducing communication overhead.
基金supported by the National Natural Science Foundation of China (21771070, 21571071)the Fundamental Research Funds for the Central Universities (2018KFYYXJJ120, 2019KFYRCPY104)~~
文摘In this study,an acid-induced assembly strategy for a rutile TiO2 photocatalyst was proposed on the basis of the treatment of lamellar protonated titanate with a concentrated HNO3 solution.Nitrate groups were successfully grafted onto a TiO2 surface and induced the assembly of rutile TiO2 nanorods into uniform spindle-like nanobundles.The resulting TiO2 product achieved a photocatalytic hydrogen evolution rate of 402.4μmol h^?1,which is 3.1 times higher than that of Degussa P25-TiO2.It was demonstrated that nitrate group grafting caused the rutile TiO2 surface to become negatively charged,which is favorable for trapping positive protons and improving charge carrier separation,thereby enhancing photocatalytic hydrogen production.Additionally,surface charges were crucial to structural stability based on electrostatic repulsion.This study not only developed a facile surface modification strategy for fabricating efficient H2 production photocatalysts but also identified an influence mechanism of inorganic acids different from that reported in the literature.
基金supported by the National Natural Science Foundation of China(21771070,21571071)~~
文摘Photocatalytic conversion of“greenhouse gas”CO2is considered to be one of the most effective ways to alleviate current energy and environmental problems without additional energy consumption and pollutant emission.The performance of many traditional semiconductor photocatalysts is not efficient enough to satisfy the requirements of practical applications because of their limited specific surface area and low CO2adsorption capacity.Therefore,the exploration of photocatalysts with high CO2uptake is significant in the field of CO2conversion.Recently the porous materials appeared to be a kind of superior candidate for enriching the CO2molecules on the surface of photocatalysts for catalytic conversion.This paper first summarizes the advances in the development of nanoporous adsorbents for CO2capture.Three main classes of porous materials are considered:inorganic porous materials,metal organic frameworks,and microporous organic polymers.Based on systematic research on CO2uptake,we then highlight the recent progress in these porous‐material‐based photocatalysts for CO2conversion.Benefiting from the improved CO2uptake capacity,the porous‐material‐based photocatalysts exhibited remarkably enhanced efficiency in the reduction of CO2to chemical fuels,such as CO,CH4,and CH3OH.Based on reported recent achievements,we predict a trend of development in multifunctional materials with both high adsorption capability and photocatalytic performance for CO2utilization.
基金supported by Army Research O ce(ARO)under Grant W911NF-16-1-0198the National Science Foundation(DMR-1709025)China Scholarship Council
文摘Electrochemical catalysts for oxygen evolution reaction are a critical component for many renewable energy applications. To improve their catalytic kinetics and mass activity are essential for sustainable industrial applications. Here, we report a rare-earth metal-based oxide electrocatalyst comprised of ultrathin amorphous La2O3 nanosheets hybridized with uniform La2O3 nanoparticles(La2O3@NP-NS). Significantly improved OER performance is observed from the nanosheets with a nanometer-scale thickness. The as-synthesized 2.27-nm La2O3@NP-NS exhibits excellent catalytic kinetics with an overpotential of 310 mV at 10 m A cm^-2, a small Tafel slope of 43.1 mV dec^-1, and electrochemical impedance of 38 Ω. More importantly, due to the ultrasmall thickness, its mass activity, and turnover frequency reach as high as 6666.7 A g^-1 and 5.79 s^-1, respectively, at an overpotential of 310 mV. Such a high mass activity is more than three orders of magnitude higher than benchmark OER electrocatalysts, such as IrO2 and RuO2. This work presents a sustainable approach toward the development of highly e cient electrocatalysts with largely reduced mass loading of precious elements.
基金supported by the National Natural Science Foundation of China(21838003,21808061 and 91534122)the Social Development Program of Shanghai(17DZ1200900)+1 种基金the Shanghai Scientific and Technological Innovation Project(18JC1410600)he Fundamental Research Funds for the Central Universities(222201718002).
文摘Tailoring valence electron delocalization of transition metal center is of importance to achieve highly-active electrocatalysts for oxygen evolution reaction(OER).Herein,we demonstrate a“poor sulfur”route to synthesize surface electron-deficient Co_(9)S_(8) nanoarrays,where the binding energy(BE)of Co metal center is considerably higher than all reported Co_(9)S_(8)-based electrocatalysts.The resulting Co_(9)S_(8) electrocatalysts only require the overpotentials(h)of 265 and 326 mV at 10 and 100 mA cm^(-2) with a low Tafel slope of 56 mV dec^-(1) and a 60 hlasting stability in alkaline media.The OER kinetics are greatly expedited with a low reaction activation energy of 27.9 kJ mol^-(1) as well as abundant OOH*key intermediates(24%),thus exhibiting excellent catalytic performances.The surface electron-deficient engineering gives an available strategy to improve the catalytic activity of other advanced non-noble electrocatalysts.
文摘The Harlem River, a 9.3-mile channel that flows from the Hudson River to the East River, has experienced decades of industrial abuse and remains gritty and industrial. During heavy rains, the pipes discharge raw sewage into the river through combined sewer overflows (CSOs) that can contain bacteria and cause illness. Water samples were collected from CSO discharge point and several adjacent sites along the river in the Bronx side close to River Park Towers at Richman Plaza and Manhattan side at Wards Island. Nutrients, bacteria, polychlorinated biphenyls (PCBs), and fish consumption safety have been analyzed. Results showed that phosphorus, ammonia concentration as well as fecal coliform, E.Coli, enterococcus levels increased significantly during heavy rainstorms. Ammonia concentration was up to 2.725 mg/L during tropical storm Arthur on July 2, 2014 and rainstorm in May 2013, and soluble reactive phosphorus (SRP) or orthophosphate was up to 0.197 mg/L during heavy thunderstorm in April 2011;both nutrients were exceeded EPA regulation for ammonia (0.23 mg/L) and phosphate (0.033 mg/L) for New York City (NYC) waters. The colonies of fecal coliform were more than 5 million MPN/100ml (most probable number per 100 ml) during tropical storm Arthur in July 2014 and heavy rainstorm in April 2014, and fecal coliform was more than 10,000 MPN/100ml during storm in July and November 2013;E.Coli reached more than 5000 MPN/100ml during tropical storm Arthur and storm in May 2013;enterococcus reached more than 10,000 MPN/100ml during tropical storm Arthur and heavy rainstorm in April 2014. These bacteria (pathogen) levels in the Harlem River were significantly higher than EPA standards (fecal coliform: 200 MPN/100ml, E.Coli: 126 MPN/100ml, enterococcus: 104 MPN/100ml), especially during rainstorm/tropical storm. Of particular significance, nutrients and bacteria were analyzed before and after Hurricane Sandy devastated NYC in late October 2012;results determined that bacteria and ammonia concentrations increased after this monumental storm, elucidating the environmental impact of large storm events. PCB 11 (3,3’-dichlorobiphenyl, C12H8Cl2), the high molecular weight (MW), an indicator of raw sewer and storm water runoff in the NYC harbor waters, is the major polychlorinated biphenyls (PCBs) in the Harlem River. PCBs are carcinogenic, which could bioaccumulate via food chain from fish and seafood, endangering public health. Oyster farming has been used to purify water and improve water quality in the river. CSOs and storm water runoff have degraded water quality and been threatening environmental ecosystem and public health. This research will help local communities understand CSO impact on nutrients, bacteria, PCBs contamination and fish consumption safety, and make contributions on CSOs reduction as well as improve water quality and environmental ecosystem in the Harlem River.
