This paper comprehensively introduces a new magnesium production technology the compound-vertical-retort technology, involving in the related fundamental researches, core equipment development, working flow, and techn...This paper comprehensively introduces a new magnesium production technology the compound-vertical-retort technology, involving in the related fundamental researches, core equipment development, working flow, and technical characteristics. Scale-up test and an annual1200-ton-magnesium demonstration-level test was conducted to confirm the rationality, reliability, and advancement of the equipment, system and process design. It is indicated that the new technology solved a series of problems of traditional silicothermic process including adhesion and glaze, short life of retort, low efficiency, high impurity of crystallized magnesium, large heat losses, and poor working environment,making a great technological breakthrough in this field. Representatively, the new well-designed ceramic-lined steel retort serves 2~3 times in life than the normal retorts. The magnesium yield per retort is improved 4~5 times, with purity of >99.8%. The energy consumption in reduction stage is reduced by more than 20%. The mechanical production is fully realized and operating environment is significantly improved.展开更多
In typical metal foundry applications,sand casting is still the most used technology.The related binder plays a very important role as its performances can directly influence the quality of castings.Among many binders...In typical metal foundry applications,sand casting is still the most used technology.The related binder plays a very important role as its performances can directly influence the quality of castings.Among many binders,glues of animal origin have attracted much attention in recent years due to their reduced environmental impact.How-ever,they display some drawbacks such as the tendency to coagulate easily at room temperature and a relatively low strength.In this study,a novel gas-hardening casting binder was prepared using an animal glue and anhy-drous potassium carbonate as a hydrolyzing agent to avoid undesired agglomeration.Moreover,sodium pyropho-sphate and furfuryl alcohol were exploited as modifiers to obtain a binder with a high compressive strength.The best modification conditions,determined by means of an orthogonal design matrix approach,were 4 g of Na2CO3,sodium pyrophosphate,furfuryl alcohol and animal glue with a ratio of 4:12:100,at 85°C and with a duration of 115 min,respectively.The viscosity of the mixture obtained under these optimized conditions was 1250 mPa⋅s.The compressive strength of the binder,hardened by CO_(2) gas,was 4.00 MPa.Its gas evolution at 850°C was 15 ml⋅g-1,and its residual strength after 10 min calculation at 800°C was 0.01 MPa,which is high enough to meet the requirement of core-making in foundry.Moreover,after hydrolysis and further modification,animal glue and modifiers displayed a grafting reaction and an esterification reaction,respectively,which made the adhesive network denser and improved its thermal stability.展开更多
Safe, green and efficient industrial production has always been the pursuit of the chemical industry. Since thermal energy is the driving force for most of chemical reactions, an ideal reaction tank would have the cap...Safe, green and efficient industrial production has always been the pursuit of the chemical industry. Since thermal energy is the driving force for most of chemical reactions, an ideal reaction tank would have the capacity to automatically regulate heat conduction rate. In detail, this reaction tank should endow an ability that resists the heat loss when the reaction temperature is lower than the target, while accelerating the heat dissipation when the system is overheated. In this case, this smart reactor can not only minimize energy consumption but also reduce safety risks.Hollow structures are known to reduce heat conductivity. Particularly, the hollow structure with multishells can provide more interfaces and thus further inhibit heat transmission, which would be more favorable for heat isolation. Step forward, by coupling HoMSs with temperature-sensitive polymer, a smart heat isolation material has been fabricated in this work. It performs as a good heat isolator at a relatively lower temperature. A heat insulation effect of 6.5℃ can be achieved for the TSPU/3S–TiO_(2)HoMSs with a thickness of 1 mm under the temperature field of 50℃.The thermal conductivity of composite material would be raised under overheating conditions. Furthermore, this composite displays an unusual two-stage phase transformation during heating. Benefiting from the unique multishelled structure, energy is found to be gradually guided into the hollow structure and stored inside. This localized heat accumulation enables the composite to be a potential coating material for intelligent thermal-regulator and site-defined micro-reactor.展开更多
China’s past economic growth has substantially relied on fossil fuels,causing serious air pollution issues.Decoupling economic growth and pollution has become the focus in developing ecological civilization in China....China’s past economic growth has substantially relied on fossil fuels,causing serious air pollution issues.Decoupling economic growth and pollution has become the focus in developing ecological civilization in China.We have analyzed the three-decade progress of air pollution controls in China,highlighting a strategic transformation from emission control toward air quality management.Emission control of sulfur dioxide(SO2)resolved the deteriorating acid rain issue in China in 2007.Since 2013,control actions on multiple precursors and sectors have targeted the reduction of the concentration of fine particulate matter(PM2.5),marking a transition to an air-quality-oriented strategy.Increasing ozone(O3)pollution further requires O3 and PM2.5 integrated control strategies with an emphasis on their complex photochemical interactions.Fundamental improvement of air quality in China,as a key indicator for the success of ecological civilization construction,demands the deep de-carbonization of China’s energy system as well as more synergistic pathways to address air pollution and global climate change simultaneously.展开更多
Effect of the second phase in the micro-galvanic corrosion of a commercial Mg alloy containing rare earth elements, cast WE43 alloy,was investigated in 0.6 M NaCl solution and 0.6 M Na_(2)SO_(4)solution by scanning el...Effect of the second phase in the micro-galvanic corrosion of a commercial Mg alloy containing rare earth elements, cast WE43 alloy,was investigated in 0.6 M NaCl solution and 0.6 M Na_(2)SO_(4)solution by scanning electron microscopy(SEM) observations, scanning Kelvin probe force microscopy(SKPFM) analysis, hydrogen evolution, weight loss measurement, and electrochemical techniques. It is confirmed that the second phase of cast WE43 alloy is more active than Mg matrix and exhibits an anodic role in the micro-galvanic corrosion with α-Mg matrix as cathode and dissolves preferentially in Na_(2)SO_(4)solution, in contrast to the situation in NaCl solution. The corrosion rate of cast WE43 alloy in Na_(2)SO_(4)solution is much higher than that in NaCl solution, which is different from the conventional wisdom and could be attributed to the different role of the second phase in the micro-galvanic corrosion in two solutions.展开更多
Network attack graphs are originally used to evaluate what the worst security state is when a concerned net-work is under attack. Combined with intrusion evidence such like IDS alerts, attack graphs can be further use...Network attack graphs are originally used to evaluate what the worst security state is when a concerned net-work is under attack. Combined with intrusion evidence such like IDS alerts, attack graphs can be further used to perform security state posterior inference (i.e. inference based on observation experience). In this area, Bayesian network is an ideal mathematic tool, however it can not be directly applied for the following three reasons: 1) in a network attack graph, there may exist directed cycles which are never permitted in a Bayesian network, 2) there may exist temporal partial ordering relations among intrusion evidence that can-not be easily modeled in a Bayesian network, and 3) just one Bayesian network cannot be used to infer both the current and the future security state of a network. In this work, we improve an approximate Bayesian posterior inference algorithm–the likelihood-weighting algorithm to resolve the above obstacles. We give out all the pseudocodes of the algorithm and use several examples to demonstrate its benefit. Based on this, we further propose a network security assessment and enhancement method along with a small network scenario to exemplify its usage.展开更多
Lattice Boltzmann method is one of the widely used in multiphase fluid flow.However,the two main disadvantages of this method are the instability of numerical calculations due to the large density ratio of two phases ...Lattice Boltzmann method is one of the widely used in multiphase fluid flow.However,the two main disadvantages of this method are the instability of numerical calculations due to the large density ratio of two phases and impossibility of the temperature distribution to be fed back into the velocity distribution function when the temperature is simulated.Based on the combination prescribed by Inamuro,the large density ratio two-phase flow model and thermal model makes the density ratio of the model simulation to be increased to 2778:1 by optimizing the interface distribution function of two-phase which improves the accuracy of differential format.The phase transition term is added as source term into the distribution function controlling two phase order parameters to describe the temperature effect on the gas-liquid phase transition.The latent heat generated from the phase change is also added as a source term into the temperature distribution function which simulates the movement of the flow under the common coupling of density,velocity,pressure and temperature.The density and the temperature distribution of single bubble are simulated.Comparison of the simulation results with experimental results indicates a good agreement pointing out the effectiveness of the improved model.展开更多
Black carbon(BC)is considered the second largest anthropogenic climate forcer,but the radiative effects of BC are highly correlated with its combustion sources.On-road vehicles are an important source of anthropogenic...Black carbon(BC)is considered the second largest anthropogenic climate forcer,but the radiative effects of BC are highly correlated with its combustion sources.On-road vehicles are an important source of anthropogenic BC.However,there are major uncertainties in the estimates of the BC emissions from on-road light-duty passenger vehicles(LDPVs),and results obtained with the portable emissions measurement system(PEMS)method are particularly lacking.We developed a PEMS platform and evaluated the on-road BC emissions from ten in-use LDPVs.We demonstrated that the BC emission factors(EFs)of gasoline direction injection(GDI)engine vehicles range from 1.10 to 1.56 mg.km^(-1),which are higher than the EFs of port fuel injection(PFI)engine vehicles(0.10–0.17 mg.km^(-1))by a factor of 11.The BC emissions during the cold-start phase contributed 2%–33%to the total emissions.A strong correlation(R^(2)=0.70)was observed between the relative BC EFs and average vehicle speed,indicating that traffic congestion alleviation could effectively mitigate BC emissions.Moreover,BC and particle number(PN)emissions were linearly correlated(R^(2)=0.90),and compared to PFI engine vehicles,the instantaneous PN-to-BC emission rates of GDI engine vehicles were less sensitive to vehicle specific power-to-velocity(VSPV)increase in all speed ranges.展开更多
Diesel vehicles have caused serious environmental problems in China.Hence,the Chinese government has launched serious actions against air pollution and imposed more stringent regulations on diesel vehicle emissions in...Diesel vehicles have caused serious environmental problems in China.Hence,the Chinese government has launched serious actions against air pollution and imposed more stringent regulations on diesel vehicle emissions in the latest China VI standard.To fulfill this stringent legislation,two major technical routes,including the exhaust gas recirculation(EGR)and high-efficiency selective catalytic reduction(SCR)routes,have been developed for diesel engines.Moreover,complicated aftertreatment technologies have also been developed,including use of a diesel oxidation catalyst(DOC)for controlling carbon monoxide(CO)and hydrocarbon(HC)emissions,diesel particulate filter(DPF)for particle mass(PM)emission control,SCR for the control of NOx emission,and an ammonia slip catalyst(ASC)for the control of unreacted NH3.Due to the stringent requirements of the China VI standard,the aftertreatment system needs to be more deeply integrated with the engine system.In the future,aftertreatment technologies will need further upgrades to fulfill the requirements of the near-zero emission target for diesel vehicles.展开更多
Exploring zinc-free anode materials is one of the effective strategies to get the zinc dendrites problem of flexible zinc ion battery(ZIB)solved.In this work,an analogous heterostructure(AHS)is constructed from the ex...Exploring zinc-free anode materials is one of the effective strategies to get the zinc dendrites problem of flexible zinc ion battery(ZIB)solved.In this work,an analogous heterostructure(AHS)is constructed from the excellent MXene(Ti_(3)C_(2)T_(x))and TiSe_(2) nanosheets.The AHS not only possesses numerous diffu-sion paths and Zn^(2+)storage sites but also possesses a stable conductive network to accelerate charge transfer in the electrode.As a collaborative advantage,electrochemical measurement results show that MXene/TiSe_(2) electrodes display an excellent specific capacity of 177.9 mAh g^(-1) at 0.10 A g^(-1) and a long-term cycling stability of 77.4%capacity retention after 400 cycles.DFT computations further demon-strate the excellent performance of MXene/TiSe_(2) electrodes including desirable electronic conductivity and low Zn^(2+)migration barriers.The assembled flexible ZIB not only delivers a good specific capacity of 42.2μAh cm^(-2) at 0.20 mA cm^(-2) and a competitive energy density of 37.4μWh cm^(-2) but also exhibits excellent flexibility and thermostability.Furthermore,after 400 cycles at 0.60 A g^(-1),flexible ZIB shows a capacity retention of 73.8%.This work gives a successful attempt to design 2D layered materials as Zn metal-free anode for flexible ZIB.展开更多
In recent years,with rapid increases in the number of vehicles in China,the contribution of vehicle exhaust emissions to air pollution has become increasingly prominent.To achieve the precise control of emissions,on-r...In recent years,with rapid increases in the number of vehicles in China,the contribution of vehicle exhaust emissions to air pollution has become increasingly prominent.To achieve the precise control of emissions,on-road remote sensing(RS)technology has been developed and applied for law enforcement and supervision.However,data quality is still an existing issue affecting the development and application of RS.In this study,the RS data from a cross-road RS system used at a single site(from 2012 to 2015)were collected,the data screening process was reviewed,the issues with data quality were summarized,a new method of data screening and calibration was proposed,and the effectiveness of the improved data quality control methods was finally evaluated.The results showed that this method reduces the skewness and kurtosis of the data distribution by up to nearly 67%,which restores the actual characteristics of exhaust diffusion and is conducive to the identification of actual clean and high-emission vehicles.The annual variability of emission factors of nitric oxide decreases by 60%-on average-eliminating the annual drift of fleet emissions and improving data reliability.展开更多
An increasing divergence regarding fuel consumption(and/or CO_(2)emissions) between realworld and type-approval values for light-duty gasoline vehicles(LDGVs) has posed severe challenges to mitigating greenhouse gases...An increasing divergence regarding fuel consumption(and/or CO_(2)emissions) between realworld and type-approval values for light-duty gasoline vehicles(LDGVs) has posed severe challenges to mitigating greenhouse gases(GHGs) and achieving carbon emissions peak and neutrality. To address this divergence issue, laboratory test cycles with more real-featured and transient traffic patterns have been developed recently, for example, the China Lightduty Vehicle Test Cycle for Passenger cars(CLTC-P). We collected fuel consumption and CO_(2)emissions data of a LDGV under various conditions based on laboratory chassis dynamometer and on-road tests. Laboratory results showed that both standard test cycles and setting methods of road load affected fuel consumption slightly, with variations of less than 4%. Compared to the type-approval value, laboratory and on-road fuel consumption of the tested LDGV over the CLTC-P increased by 9% and 34% under the reference condition(i.e., air conditioning off, automatic stop and start(STT) on and two passengers). On-road measurement results indicated that fuel consumption under the low-speed phase of the CLTC-P increased by 12% due to the STT off, although only a 4% increase on average over the entire cycle. More fuel consumption increases(52%) were attributed to air conditioning usage and full passenger capacity. Strong correlations(R2> 0.9) between relative fuel consumption and average speed were also identified. Under traffic congestion(average speed below 25 km/hr), fuel consumption was highly sensitive to changes in vehicle speed. Thus,we suggest that real-world driving conditions cannot be ignored when evaluating the fuel economy and GHGs reduction of LDGVs.展开更多
It is well recognized that carbon dioxide and air pollutants share similar emission sources so that synergetic policies on climate change mitigation and air pollution control can lead to remarkable co-benefits on gree...It is well recognized that carbon dioxide and air pollutants share similar emission sources so that synergetic policies on climate change mitigation and air pollution control can lead to remarkable co-benefits on greenhouse gas reduction,air quality improvement,and improved health.In the context of carbon peak,carbon neutrality,and clean air policies,this perspective tracks and analyzes the process of the synergetic governance of air pollution and climate change in China by developing and monitoring 18 indicators.The 18 indicators cover the following five aspects:air pollution and associated weather-climate conditions,progress in structural transition,sources,inks,and mitigation pathway of atmospheric composition,health impacts and benefits of coordinated control,and synergetic governance system and practices.By tracking the progress in each indicator,this perspective presents the major accomplishment of coordinated control,identifies the emerging challenges toward the synergetic governance,and provides policy recommendations for designing a synergetic roadmap of Carbon Neutrality and Clean Air for China.展开更多
Accelerating the building of a new development pattern with domestic market as the mainstay and domestic and international markets reinforcing each other is a major decision made by the CPC Central Committee with Comr...Accelerating the building of a new development pattern with domestic market as the mainstay and domestic and international markets reinforcing each other is a major decision made by the CPC Central Committee with Comrade Xi Jinping at the core in light of changes in the development stage,environment and conditions in China.Trade gains are an important indicator of the development trend of domestic and international circulations for a country.With the quantitative model of trade gains containing the multi-sectoral input-output relations,this paper estimates the trade gains from the economic dual circulation in China between 1987 and 2017,based on the kernel density estimation and Markov chain,and the main findings are as follows.(1)The trade gains from the domestic circulation in China showed a downward trend,while the trade gains from the international circulation presented a trend of first rising and then declining.But the former still outweighed the latter.(2)Compared with the international circulation,the continuity,spatial correlation effect and rising potential of the trade gains from China's domestic circulation were greater.(3)There was no positive spatial correlation effect between the trade gains from the domestic and those from the international circulation.China should make overall plans for opening up both externally and internally,and unblock sticking points between the two circulations,so as to realize the positive interaction of the trade gains from the dual circulation,and accelerate the formation of a new development pattern with domestic market as the mainstay and domestic and international markets reinforcing each other.展开更多
In China, the health risk from overexposure to particles is becoming an important public health concern. To investigate daily exposure characteristics to PM 2.5 with high ambient concentration in urban area, a persona...In China, the health risk from overexposure to particles is becoming an important public health concern. To investigate daily exposure characteristics to PM 2.5 with high ambient concentration in urban area, a personal exposure study was conducted for school children, and office workers in Beijing, China. For all participants (N = 114), the mean personal 24-hr exposure concentration was 102.5, 14.7, 0.093, 0.528, 0.934, 0.174 and 0.703 μg/m 3 for PM 2.5 , black carbon, Mn, Al, Ca, Pb, and Fe. Children's exposure concentrations of PM 2.5 were 4-5 times higher than those in related studies. The ambient concentration of PM 2.5 (128.5 μg/m 3 ) was significantly higher than the personal exposure concentration (P < 0.05), and exceed the reference concentration (25 μg/m 3 ) of WHO air quality guideline. Good correlation relationships and significant differences were identified between ambient concentration and personal exposure concentration. The relationships indicate that the ambient concentration is the main factor influencing personal exposure concentration, but is not a good indicator of personal exposure concentration. Outdoor activities (commute mode, exposure to heating, workday or weekend travel) influenced personal exposure concentrations significantly, but the magnitude of the influence from indoor activities (exposure to cooking) was masked by the high ambient concentrations.展开更多
The Yangtze River Delta(YRD) region is one of the most prosperous and densely populated regions in China and is facing tremendous pressure to mitigate vehicle emissions and improve air quality.Our assessment has revea...The Yangtze River Delta(YRD) region is one of the most prosperous and densely populated regions in China and is facing tremendous pressure to mitigate vehicle emissions and improve air quality.Our assessment has revealed that mitigating vehicle emissions of NOx would be more difficult than reducing the emissions of other major vehicular pollutants(e.g.,CO,HC and PM_(2.5)) in the YRD region.Even in Shanghai,where the emission control implemented are more stringent than in Jiangsu and Zhejiang,we observed little to no reduction in NOx emissions from 2000 to 2010.Emission-reduction targets for HC,NOx and PM_(2.5) are determined using a response surface modeling tool for better air quality.We design city-specific emission control strategies for three vehicle-populated cities in the YRD region:Shanghai and Nanjing and Wuxi in Jiangsu.Our results indicate that even if stringent emission control consisting of the Euro 6/VI standards,the limitation of vehicle population and usage,and the scrappage of older vehicles is applied,Nanjing and Wuxi will not be able to meet the NOx emissions target by 2020.Therefore,additional control measures are proposed for Nanjing and Wuxi to further mitigate NOx emissions from heavy-duty diesel vehicles.展开更多
Roadside remote sensing measurement was used to explore the real-world emission status of light duty gasoline vehicles(LDGVs) and motorcycles in Macao. Both fuel-based and distance-based emission factors were derived ...Roadside remote sensing measurement was used to explore the real-world emission status of light duty gasoline vehicles(LDGVs) and motorcycles in Macao. Both fuel-based and distance-based emission factors were derived using the mass balance method. The emission concentration profile of LDGVs illustrated the benefits of tightening emission standards at the source country or region of import. The distance-based emission factors for CO, HC and NOx of LDGVs registered before 2000 were 8.00, 1.04 and 1.36 g/km,respectively. The distance-based emission factors for CO, HC and NOx of LDGVs registered in or after 2000 were 1.16, 0.15 and 0.18 g/km, respectively. The fuel-based CO emission factors of light duty motorcycles(LDMCs) and heavy duty motorcycles(HDMCs) registered before 2000 were about 10 times higher than those of LDGVs of the same age group. As the emissions of LDGVs decreased more quickly after 2000, the gap widens for newer vehicles.The distance-based HC emission factors of LDMCs and HDMCs registered before 2000 were4.81 and 2.91 g/km, respectively. The distance-based HC emission factors of LDMCs and HDMCs registered in or after 2000 were 3.52 and 0.93 g/km, respectively. The poor emission performance of motorcycles and their larger share in the traffic flow will cause them to be the major contributor to traffic CO and HC emissions. LDMCs, especially two-stroke models,should be the priority for vehicle emission control efforts in Macao.展开更多
Molybdenum dialkyldithiocarbamate(MoDTC)is widely used as a friction modifier in engine lubricating oil.Under MoDTC lubrication,the friction and wear behaviors of tungsten-doped diamond-like carbon(W-DLC)films anneale...Molybdenum dialkyldithiocarbamate(MoDTC)is widely used as a friction modifier in engine lubricating oil.Under MoDTC lubrication,the friction and wear behaviors of tungsten-doped diamond-like carbon(W-DLC)films annealed at 100-400℃were discussed and evaluated using scanning electron microscopy(SEM),atomic force microscopy(AFM),and Raman spectroscopy.Under(polymerized alpha olefin)PAO+MoDTC lubrication,the coefficient of friction of all samples decreased,but the wear rates of the W-DLC films annealed at 300℃increased significantly.By interacting with zinc dialkyldithiophosphate(ZDDP),the wear rates of W-DLC films annealed at different temperatures declined significantly owing to the formation of dense phosphate tribofilms on the worn surfaces.展开更多
基金the financial support from the Zhengzhou Collaborative Innovation Major Funding (18XTZX12010)National Key Research and Development Project (2016YFB0301101)Baosteel Metals Co.,Ltd.
文摘This paper comprehensively introduces a new magnesium production technology the compound-vertical-retort technology, involving in the related fundamental researches, core equipment development, working flow, and technical characteristics. Scale-up test and an annual1200-ton-magnesium demonstration-level test was conducted to confirm the rationality, reliability, and advancement of the equipment, system and process design. It is indicated that the new technology solved a series of problems of traditional silicothermic process including adhesion and glaze, short life of retort, low efficiency, high impurity of crystallized magnesium, large heat losses, and poor working environment,making a great technological breakthrough in this field. Representatively, the new well-designed ceramic-lined steel retort serves 2~3 times in life than the normal retorts. The magnesium yield per retort is improved 4~5 times, with purity of >99.8%. The energy consumption in reduction stage is reduced by more than 20%. The mechanical production is fully realized and operating environment is significantly improved.
基金supported by the National Natural Science Foundation of China(51275313)Shandong Province Transportation Science and Technology Project(2021B115)Shandong Jiaotong University School Fund(Z2019036).
文摘In typical metal foundry applications,sand casting is still the most used technology.The related binder plays a very important role as its performances can directly influence the quality of castings.Among many binders,glues of animal origin have attracted much attention in recent years due to their reduced environmental impact.How-ever,they display some drawbacks such as the tendency to coagulate easily at room temperature and a relatively low strength.In this study,a novel gas-hardening casting binder was prepared using an animal glue and anhy-drous potassium carbonate as a hydrolyzing agent to avoid undesired agglomeration.Moreover,sodium pyropho-sphate and furfuryl alcohol were exploited as modifiers to obtain a binder with a high compressive strength.The best modification conditions,determined by means of an orthogonal design matrix approach,were 4 g of Na2CO3,sodium pyrophosphate,furfuryl alcohol and animal glue with a ratio of 4:12:100,at 85°C and with a duration of 115 min,respectively.The viscosity of the mixture obtained under these optimized conditions was 1250 mPa⋅s.The compressive strength of the binder,hardened by CO_(2) gas,was 4.00 MPa.Its gas evolution at 850°C was 15 ml⋅g-1,and its residual strength after 10 min calculation at 800°C was 0.01 MPa,which is high enough to meet the requirement of core-making in foundry.Moreover,after hydrolysis and further modification,animal glue and modifiers displayed a grafting reaction and an esterification reaction,respectively,which made the adhesive network denser and improved its thermal stability.
基金financially supported by the National Natural Science Foundation of China (Nos.21931012,21971244,92163209,and 52174387)the Education Department of Henan Province (No.20A430024)。
文摘Safe, green and efficient industrial production has always been the pursuit of the chemical industry. Since thermal energy is the driving force for most of chemical reactions, an ideal reaction tank would have the capacity to automatically regulate heat conduction rate. In detail, this reaction tank should endow an ability that resists the heat loss when the reaction temperature is lower than the target, while accelerating the heat dissipation when the system is overheated. In this case, this smart reactor can not only minimize energy consumption but also reduce safety risks.Hollow structures are known to reduce heat conductivity. Particularly, the hollow structure with multishells can provide more interfaces and thus further inhibit heat transmission, which would be more favorable for heat isolation. Step forward, by coupling HoMSs with temperature-sensitive polymer, a smart heat isolation material has been fabricated in this work. It performs as a good heat isolator at a relatively lower temperature. A heat insulation effect of 6.5℃ can be achieved for the TSPU/3S–TiO_(2)HoMSs with a thickness of 1 mm under the temperature field of 50℃.The thermal conductivity of composite material would be raised under overheating conditions. Furthermore, this composite displays an unusual two-stage phase transformation during heating. Benefiting from the unique multishelled structure, energy is found to be gradually guided into the hollow structure and stored inside. This localized heat accumulation enables the composite to be a potential coating material for intelligent thermal-regulator and site-defined micro-reactor.
基金the National Key Research Development Program of China(2016YFC0208901 and 2017YFC0212100)the National Natural Science Foundation of China(71722003 and 71690244)。
文摘China’s past economic growth has substantially relied on fossil fuels,causing serious air pollution issues.Decoupling economic growth and pollution has become the focus in developing ecological civilization in China.We have analyzed the three-decade progress of air pollution controls in China,highlighting a strategic transformation from emission control toward air quality management.Emission control of sulfur dioxide(SO2)resolved the deteriorating acid rain issue in China in 2007.Since 2013,control actions on multiple precursors and sectors have targeted the reduction of the concentration of fine particulate matter(PM2.5),marking a transition to an air-quality-oriented strategy.Increasing ozone(O3)pollution further requires O3 and PM2.5 integrated control strategies with an emphasis on their complex photochemical interactions.Fundamental improvement of air quality in China,as a key indicator for the success of ecological civilization construction,demands the deep de-carbonization of China’s energy system as well as more synergistic pathways to address air pollution and global climate change simultaneously.
基金funded by the National Key Research and Development Program of China (Grant No. 2016YFB0301001 and 2016YFB0301101)Major Projects for Collaborative Innovation of Zhengzhou (Grant No.18XTZX12010)Certificate of Postdoctoral Research Grant in Henan Province (Grant No. 201903011)。
文摘Effect of the second phase in the micro-galvanic corrosion of a commercial Mg alloy containing rare earth elements, cast WE43 alloy,was investigated in 0.6 M NaCl solution and 0.6 M Na_(2)SO_(4)solution by scanning electron microscopy(SEM) observations, scanning Kelvin probe force microscopy(SKPFM) analysis, hydrogen evolution, weight loss measurement, and electrochemical techniques. It is confirmed that the second phase of cast WE43 alloy is more active than Mg matrix and exhibits an anodic role in the micro-galvanic corrosion with α-Mg matrix as cathode and dissolves preferentially in Na_(2)SO_(4)solution, in contrast to the situation in NaCl solution. The corrosion rate of cast WE43 alloy in Na_(2)SO_(4)solution is much higher than that in NaCl solution, which is different from the conventional wisdom and could be attributed to the different role of the second phase in the micro-galvanic corrosion in two solutions.
文摘Network attack graphs are originally used to evaluate what the worst security state is when a concerned net-work is under attack. Combined with intrusion evidence such like IDS alerts, attack graphs can be further used to perform security state posterior inference (i.e. inference based on observation experience). In this area, Bayesian network is an ideal mathematic tool, however it can not be directly applied for the following three reasons: 1) in a network attack graph, there may exist directed cycles which are never permitted in a Bayesian network, 2) there may exist temporal partial ordering relations among intrusion evidence that can-not be easily modeled in a Bayesian network, and 3) just one Bayesian network cannot be used to infer both the current and the future security state of a network. In this work, we improve an approximate Bayesian posterior inference algorithm–the likelihood-weighting algorithm to resolve the above obstacles. We give out all the pseudocodes of the algorithm and use several examples to demonstrate its benefit. Based on this, we further propose a network security assessment and enhancement method along with a small network scenario to exemplify its usage.
基金supported by the National Natural Science Foundation of China (51609131)Shandong Provincial Natural Science Foundation of China (ZR2017MEE031)+1 种基金 Weihai Science and Technology Development Plan (2017GNS18)Shandong Provincial Higher Educational Science and Technology Foundation of China (J16LA61)
文摘Lattice Boltzmann method is one of the widely used in multiphase fluid flow.However,the two main disadvantages of this method are the instability of numerical calculations due to the large density ratio of two phases and impossibility of the temperature distribution to be fed back into the velocity distribution function when the temperature is simulated.Based on the combination prescribed by Inamuro,the large density ratio two-phase flow model and thermal model makes the density ratio of the model simulation to be increased to 2778:1 by optimizing the interface distribution function of two-phase which improves the accuracy of differential format.The phase transition term is added as source term into the distribution function controlling two phase order parameters to describe the temperature effect on the gas-liquid phase transition.The latent heat generated from the phase change is also added as a source term into the temperature distribution function which simulates the movement of the flow under the common coupling of density,velocity,pressure and temperature.The density and the temperature distribution of single bubble are simulated.Comparison of the simulation results with experimental results indicates a good agreement pointing out the effectiveness of the improved model.
基金supported by the National Natural Science Foundation of China(51708327 and 51978404)。
文摘Black carbon(BC)is considered the second largest anthropogenic climate forcer,but the radiative effects of BC are highly correlated with its combustion sources.On-road vehicles are an important source of anthropogenic BC.However,there are major uncertainties in the estimates of the BC emissions from on-road light-duty passenger vehicles(LDPVs),and results obtained with the portable emissions measurement system(PEMS)method are particularly lacking.We developed a PEMS platform and evaluated the on-road BC emissions from ten in-use LDPVs.We demonstrated that the BC emission factors(EFs)of gasoline direction injection(GDI)engine vehicles range from 1.10 to 1.56 mg.km^(-1),which are higher than the EFs of port fuel injection(PFI)engine vehicles(0.10–0.17 mg.km^(-1))by a factor of 11.The BC emissions during the cold-start phase contributed 2%–33%to the total emissions.A strong correlation(R^(2)=0.70)was observed between the relative BC EFs and average vehicle speed,indicating that traffic congestion alleviation could effectively mitigate BC emissions.Moreover,BC and particle number(PN)emissions were linearly correlated(R^(2)=0.90),and compared to PFI engine vehicles,the instantaneous PN-to-BC emission rates of GDI engine vehicles were less sensitive to vehicle specific power-to-velocity(VSPV)increase in all speed ranges.
基金supported by the National Key R&D Program of China(No.2017YFC0211101)the Key Project of National Natural Science Foundation(No.21637005)+1 种基金the Cultivating Project of Strategic Priority Research Program of Chinese Academy of Sciences(No.XDPB1902)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23010200)。
文摘Diesel vehicles have caused serious environmental problems in China.Hence,the Chinese government has launched serious actions against air pollution and imposed more stringent regulations on diesel vehicle emissions in the latest China VI standard.To fulfill this stringent legislation,two major technical routes,including the exhaust gas recirculation(EGR)and high-efficiency selective catalytic reduction(SCR)routes,have been developed for diesel engines.Moreover,complicated aftertreatment technologies have also been developed,including use of a diesel oxidation catalyst(DOC)for controlling carbon monoxide(CO)and hydrocarbon(HC)emissions,diesel particulate filter(DPF)for particle mass(PM)emission control,SCR for the control of NOx emission,and an ammonia slip catalyst(ASC)for the control of unreacted NH3.Due to the stringent requirements of the China VI standard,the aftertreatment system needs to be more deeply integrated with the engine system.In the future,aftertreatment technologies will need further upgrades to fulfill the requirements of the near-zero emission target for diesel vehicles.
基金supported by the National Natural Science Foundation of China (Nos.12004002 and 12274151)Anhui Provincial Natural Science Foundation (No.1908085QF251)Foundation for Introduction of High-Level Talents of Anhui University (No.S020118002/061).
文摘Exploring zinc-free anode materials is one of the effective strategies to get the zinc dendrites problem of flexible zinc ion battery(ZIB)solved.In this work,an analogous heterostructure(AHS)is constructed from the excellent MXene(Ti_(3)C_(2)T_(x))and TiSe_(2) nanosheets.The AHS not only possesses numerous diffu-sion paths and Zn^(2+)storage sites but also possesses a stable conductive network to accelerate charge transfer in the electrode.As a collaborative advantage,electrochemical measurement results show that MXene/TiSe_(2) electrodes display an excellent specific capacity of 177.9 mAh g^(-1) at 0.10 A g^(-1) and a long-term cycling stability of 77.4%capacity retention after 400 cycles.DFT computations further demon-strate the excellent performance of MXene/TiSe_(2) electrodes including desirable electronic conductivity and low Zn^(2+)migration barriers.The assembled flexible ZIB not only delivers a good specific capacity of 42.2μAh cm^(-2) at 0.20 mA cm^(-2) and a competitive energy density of 37.4μWh cm^(-2) but also exhibits excellent flexibility and thermostability.Furthermore,after 400 cycles at 0.60 A g^(-1),flexible ZIB shows a capacity retention of 73.8%.This work gives a successful attempt to design 2D layered materials as Zn metal-free anode for flexible ZIB.
基金supported by National Key R&D Program of China(Nos.2019YFC0214800 and 2017YFC0212100)Beijing Municipal Science&Technology Commission(No.Z181100005418015)。
文摘In recent years,with rapid increases in the number of vehicles in China,the contribution of vehicle exhaust emissions to air pollution has become increasingly prominent.To achieve the precise control of emissions,on-road remote sensing(RS)technology has been developed and applied for law enforcement and supervision.However,data quality is still an existing issue affecting the development and application of RS.In this study,the RS data from a cross-road RS system used at a single site(from 2012 to 2015)were collected,the data screening process was reviewed,the issues with data quality were summarized,a new method of data screening and calibration was proposed,and the effectiveness of the improved data quality control methods was finally evaluated.The results showed that this method reduces the skewness and kurtosis of the data distribution by up to nearly 67%,which restores the actual characteristics of exhaust diffusion and is conducive to the identification of actual clean and high-emission vehicles.The annual variability of emission factors of nitric oxide decreases by 60%-on average-eliminating the annual drift of fleet emissions and improving data reliability.
基金sponsored by the National Natural Science Foundation of China (Nos. 52170111 and 41977180)the first China First Automobile Works (FAW)-Volkswagen China Environmental Protection Foundation automobile environmental protection innovation leading plan。
文摘An increasing divergence regarding fuel consumption(and/or CO_(2)emissions) between realworld and type-approval values for light-duty gasoline vehicles(LDGVs) has posed severe challenges to mitigating greenhouse gases(GHGs) and achieving carbon emissions peak and neutrality. To address this divergence issue, laboratory test cycles with more real-featured and transient traffic patterns have been developed recently, for example, the China Lightduty Vehicle Test Cycle for Passenger cars(CLTC-P). We collected fuel consumption and CO_(2)emissions data of a LDGV under various conditions based on laboratory chassis dynamometer and on-road tests. Laboratory results showed that both standard test cycles and setting methods of road load affected fuel consumption slightly, with variations of less than 4%. Compared to the type-approval value, laboratory and on-road fuel consumption of the tested LDGV over the CLTC-P increased by 9% and 34% under the reference condition(i.e., air conditioning off, automatic stop and start(STT) on and two passengers). On-road measurement results indicated that fuel consumption under the low-speed phase of the CLTC-P increased by 12% due to the STT off, although only a 4% increase on average over the entire cycle. More fuel consumption increases(52%) were attributed to air conditioning usage and full passenger capacity. Strong correlations(R2> 0.9) between relative fuel consumption and average speed were also identified. Under traffic congestion(average speed below 25 km/hr), fuel consumption was highly sensitive to changes in vehicle speed. Thus,we suggest that real-world driving conditions cannot be ignored when evaluating the fuel economy and GHGs reduction of LDGVs.
基金This work was supported by the National Natural Science Foundation of China(41921005,42130708,and 72140003)and the Energy Foundation.
文摘It is well recognized that carbon dioxide and air pollutants share similar emission sources so that synergetic policies on climate change mitigation and air pollution control can lead to remarkable co-benefits on greenhouse gas reduction,air quality improvement,and improved health.In the context of carbon peak,carbon neutrality,and clean air policies,this perspective tracks and analyzes the process of the synergetic governance of air pollution and climate change in China by developing and monitoring 18 indicators.The 18 indicators cover the following five aspects:air pollution and associated weather-climate conditions,progress in structural transition,sources,inks,and mitigation pathway of atmospheric composition,health impacts and benefits of coordinated control,and synergetic governance system and practices.By tracking the progress in each indicator,this perspective presents the major accomplishment of coordinated control,identifies the emerging challenges toward the synergetic governance,and provides policy recommendations for designing a synergetic roadmap of Carbon Neutrality and Clean Air for China.
基金This paper is supported by the General Project of National Natural Science Foundation of China(71873112)the Key Project of National Natural Science Foundation of China(71733003).
文摘Accelerating the building of a new development pattern with domestic market as the mainstay and domestic and international markets reinforcing each other is a major decision made by the CPC Central Committee with Comrade Xi Jinping at the core in light of changes in the development stage,environment and conditions in China.Trade gains are an important indicator of the development trend of domestic and international circulations for a country.With the quantitative model of trade gains containing the multi-sectoral input-output relations,this paper estimates the trade gains from the economic dual circulation in China between 1987 and 2017,based on the kernel density estimation and Markov chain,and the main findings are as follows.(1)The trade gains from the domestic circulation in China showed a downward trend,while the trade gains from the international circulation presented a trend of first rising and then declining.But the former still outweighed the latter.(2)Compared with the international circulation,the continuity,spatial correlation effect and rising potential of the trade gains from China's domestic circulation were greater.(3)There was no positive spatial correlation effect between the trade gains from the domestic and those from the international circulation.China should make overall plans for opening up both externally and internally,and unblock sticking points between the two circulations,so as to realize the positive interaction of the trade gains from the dual circulation,and accelerate the formation of a new development pattern with domestic market as the mainstay and domestic and international markets reinforcing each other.
基金supported by the National Natural Science Foundation of China(No.50778100) funded in part by Afton Chemical Corporation
文摘In China, the health risk from overexposure to particles is becoming an important public health concern. To investigate daily exposure characteristics to PM 2.5 with high ambient concentration in urban area, a personal exposure study was conducted for school children, and office workers in Beijing, China. For all participants (N = 114), the mean personal 24-hr exposure concentration was 102.5, 14.7, 0.093, 0.528, 0.934, 0.174 and 0.703 μg/m 3 for PM 2.5 , black carbon, Mn, Al, Ca, Pb, and Fe. Children's exposure concentrations of PM 2.5 were 4-5 times higher than those in related studies. The ambient concentration of PM 2.5 (128.5 μg/m 3 ) was significantly higher than the personal exposure concentration (P < 0.05), and exceed the reference concentration (25 μg/m 3 ) of WHO air quality guideline. Good correlation relationships and significant differences were identified between ambient concentration and personal exposure concentration. The relationships indicate that the ambient concentration is the main factor influencing personal exposure concentration, but is not a good indicator of personal exposure concentration. Outdoor activities (commute mode, exposure to heating, workday or weekend travel) influenced personal exposure concentrations significantly, but the magnitude of the influence from indoor activities (exposure to cooking) was masked by the high ambient concentrations.
基金sponsored by the National Science&Technology Pillar Program of China(No.2013BAC13B03)the National Natural Science Foundation of China(Nos.51322804 and 91544222)
文摘The Yangtze River Delta(YRD) region is one of the most prosperous and densely populated regions in China and is facing tremendous pressure to mitigate vehicle emissions and improve air quality.Our assessment has revealed that mitigating vehicle emissions of NOx would be more difficult than reducing the emissions of other major vehicular pollutants(e.g.,CO,HC and PM_(2.5)) in the YRD region.Even in Shanghai,where the emission control implemented are more stringent than in Jiangsu and Zhejiang,we observed little to no reduction in NOx emissions from 2000 to 2010.Emission-reduction targets for HC,NOx and PM_(2.5) are determined using a response surface modeling tool for better air quality.We design city-specific emission control strategies for three vehicle-populated cities in the YRD region:Shanghai and Nanjing and Wuxi in Jiangsu.Our results indicate that even if stringent emission control consisting of the Euro 6/VI standards,the limitation of vehicle population and usage,and the scrappage of older vehicles is applied,Nanjing and Wuxi will not be able to meet the NOx emissions target by 2020.Therefore,additional control measures are proposed for Nanjing and Wuxi to further mitigate NOx emissions from heavy-duty diesel vehicles.
基金supported by the Macao Environmental Protection Bureau
文摘Roadside remote sensing measurement was used to explore the real-world emission status of light duty gasoline vehicles(LDGVs) and motorcycles in Macao. Both fuel-based and distance-based emission factors were derived using the mass balance method. The emission concentration profile of LDGVs illustrated the benefits of tightening emission standards at the source country or region of import. The distance-based emission factors for CO, HC and NOx of LDGVs registered before 2000 were 8.00, 1.04 and 1.36 g/km,respectively. The distance-based emission factors for CO, HC and NOx of LDGVs registered in or after 2000 were 1.16, 0.15 and 0.18 g/km, respectively. The fuel-based CO emission factors of light duty motorcycles(LDMCs) and heavy duty motorcycles(HDMCs) registered before 2000 were about 10 times higher than those of LDGVs of the same age group. As the emissions of LDGVs decreased more quickly after 2000, the gap widens for newer vehicles.The distance-based HC emission factors of LDMCs and HDMCs registered before 2000 were4.81 and 2.91 g/km, respectively. The distance-based HC emission factors of LDMCs and HDMCs registered in or after 2000 were 3.52 and 0.93 g/km, respectively. The poor emission performance of motorcycles and their larger share in the traffic flow will cause them to be the major contributor to traffic CO and HC emissions. LDMCs, especially two-stroke models,should be the priority for vehicle emission control efforts in Macao.
基金This work was supported by the National Natural Science Foundation of China(31371314 and 81673460)Sichuan Youth Science and Technology Innovation Research Team of Experimental Formulology(2020JDTD0022).
基金This research was financially supported by the National Natural Science Foundation of China(Nos.51875537 and 41872183)the Pre-Research Program in National 14th Five-Year Plan(No.61409230614)the Fundamental Research Funds for the Central University(No.2652018094).
文摘Molybdenum dialkyldithiocarbamate(MoDTC)is widely used as a friction modifier in engine lubricating oil.Under MoDTC lubrication,the friction and wear behaviors of tungsten-doped diamond-like carbon(W-DLC)films annealed at 100-400℃were discussed and evaluated using scanning electron microscopy(SEM),atomic force microscopy(AFM),and Raman spectroscopy.Under(polymerized alpha olefin)PAO+MoDTC lubrication,the coefficient of friction of all samples decreased,but the wear rates of the W-DLC films annealed at 300℃increased significantly.By interacting with zinc dialkyldithiophosphate(ZDDP),the wear rates of W-DLC films annealed at different temperatures declined significantly owing to the formation of dense phosphate tribofilms on the worn surfaces.
