The coordinated control of PM_(2.5)and ozone has become the strategic goal of national air pollution control.Considering the gradual decline in PM_(2.5)concentration and the aggravation of ozone pollution,a better und...The coordinated control of PM_(2.5)and ozone has become the strategic goal of national air pollution control.Considering the gradual decline in PM_(2.5)concentration and the aggravation of ozone pollution,a better understanding of the coordinated control of PM_(2.5)and ozone is urgently needed.Here,we collected and sorted air pollutant data for 337 cities from 2015 to 2020 to explore the characteristics of PM_(2.5)and ozone pollution based on China’s five major air pollution regions.The results show that it is necessary to continue to strengthen the emission reduction in PM_(2.5)and ozone precursors,and control NO_(x) and VOCs while promoting a dramatic emission reduction in PM_(2.5).The primary method of curbing ozone pollution is to strengthen the emission control of VOCs,with a long-term strategy of achieving substantial emission reductions in NO_(x),because VOCs and NO_(x) are also precursors to PM_(2.5);hence,their reductions also contribute to the reduction in PM_(2.5).Therefore,the implementation of a multipollutant emission reduction control strategy aimed at the prevention and control of PM_(2.5)and ozone pollution is the only means to realize the coordinated control of PM_(2.5)and ozone.展开更多
The evaluation of the efficiency and feasibility of energy transition and air pollution control at the city level is one of the key points in addressing environmental problems and achieving the goals of CO_(2) emissio...The evaluation of the efficiency and feasibility of energy transition and air pollution control at the city level is one of the key points in addressing environmental problems and achieving the goals of CO_(2) emission reduction and carbon neutrality in China. In this study, an integrated method is developed on the basis of the Low Emissions Analysis Platform (LEAP) and life cycle assessment (LCA). The energy demands and environmental co-benefits in Jinan, one of the low-carbon city pilots in China, are quantitatively evaluated under three policy scenarios: low-carbon (LC) policy scenario, pollution control (PC) policy scenario, and deep-level cut of CO_(2) emissions (DCC) scenario from 2016 to 2050. From 2016 to 2030, the PC policies would be more powerful than the LC policies in terms of energy demand decrease. From 2030 to 2050, the LC policies would be more efficient than all the other policies. Promoting energy-saving buildings in the LC scenario would contribute to the continual decline in energy demands. In the DCC scenario, CO_(2), PM_(2.5), PM_(10), CO, NO_(X) and SO_(2) emissions would decline by more than 71.4% relative to the records in 2016. Global warming potential, human toxicity potential, photochemical ozone creation potential, particulate matter formation potential, and acidification potential would also decrease by 81.8%–88.5%. On the basis of the integrated city-level LEAP and LCA method, this study quantifies the various environmental impacts of urban decarbonization policies and provides science-based references for urban low-carbon transformation.展开更多
Synthesis of stable main-group element-based radicals represents one of the most interesting topics in contemporary organometallic chem- istry, because of their vital roles in organic, inorganic and biological chemist...Synthesis of stable main-group element-based radicals represents one of the most interesting topics in contemporary organometallic chem- istry, because of their vital roles in organic, inorganic and biological chemistry as well as materials science. However, the access of stable main-group element-based radicals is highly challenging owing to the lack of energetically accessible orbitals in the main-group elements. During the last decades, several synthetic strategies have been developed in obtaining these reactive species. Among them, utilizing the stericaliy demanding substituents and x-conjugated ligands has proven to be an effective approach. Weakly coordinating ions （WCAs） have also been found to be exceptionally practical in synthesizing radical cations of main-group elements. By introducing these stabilization methods, we have successfully prepared a variety of radical ions of p-block elements in the crystalline forms, and investigated their properties by different experimental and quantum chemical calculation methods. According to the investigations, magnetic stability was observed, resulting from the intramolecular electron-exchange interaction. Furthermore, we also found that the singlet-triptet energy gaps of the bis（triarylamine） diradical dications can be tunable by varying the temperature. These investigations open new avenues of the main-group element-based radicals for a large variety of applications.展开更多
The implementation of pristine covalent organic polymer(CO_(2)P)with well-defined structure as air electrode may spark fresh vitality to rechargeable zinc-air flow batteries(ZAFBs),but it still remains challenges in s...The implementation of pristine covalent organic polymer(CO_(2)P)with well-defined structure as air electrode may spark fresh vitality to rechargeable zinc-air flow batteries(ZAFBs),but it still remains challenges in synergistically regulating their electronic states and structural porosity for the great device performance.Here,we conquer these issues by exploiting N and S co-doped graphene with COP rich in metal-ligand nitrogen to synergistically construct an effective catalyst for oxygen reduction reaction(ORR).Among them,the N and S co-doped sites with high electronegativity properties alter the number of electron occupations in the d orbital of the iron centre and form electron-transfer bridges,thereby boosting the selectivity of the ORR-catalysed four-electron pathway.Meanwhile,the introduction of COP materials aids the formation of pore interstices in the graphene lamellae,which both adequately expose the active sites and facilitate the transport of reactive substances.Benefiting from the synergistic effect,as-prepared catalyst exhibits excellent half-wave potentials(E_(1/2)=912 mV)and stability(merely 8.8%drop after a long-term durability test of 50000 s).Further,ZAFBs assembled with the N/SG@CO_(2)P catalyst demonstrate exceptional power density(163.8 mW cm^(-2))and continuous charge and discharge for approximately 140 h at 10 mA cm^(-2),outperforming the noble-metal benchmarks.展开更多
Walking is a complex task which includes hundreds of muscles, bones and joints working together to deliver smooth movements. With the complexity, walking has been widely investigated in order to identify the pattern o...Walking is a complex task which includes hundreds of muscles, bones and joints working together to deliver smooth movements. With the complexity, walking has been widely investigated in order to identify the pattern of multi-segment movement and reveal the control mechanism. The degree of freedom and dimensional properties provide a view of the coordinative structure during walking, which has been extensively studied by using dimension reduction technique. In this paper, the studies related to the coordinative structure, dimensions detection and pattern reorganization during walking have been reviewed. Principal component analysis, as a popular technique, is widely used in the processing of human movement data. Both the principle and the outcomes of principal component analysis were introduced in this paper. This technique has been reported to successfully reduce the redundancy within the original data, identify the physical meaning represented by the extracted principal components and discriminate the different patterns. The coordinative structure during walking assessed by this technique could provide further information of the body control mechanism and correlate walking pattern with injury.展开更多
A sliding mode variable structure control （SMVSC） based on a coordinating optimization algorithm has been developed. Steady state error and control switching frequency are used to constitute the system performance i...A sliding mode variable structure control （SMVSC） based on a coordinating optimization algorithm has been developed. Steady state error and control switching frequency are used to constitute the system performance indexes in the coordinating optimization, while the tuning rate of boundary layer width （BLW） is employed as the optimization parameter. Based on the mathematical relationship between the BLW and steady-state error, an optimized BLW tuning rate is added to the nonlinear control term of SMVSC. Simulation experiment results applied to the positioning control of an electro-hydraulic servo system show the comprehensive superiority in dynamical and static state performance by using the proposed controller is better than that by using SMVSC without optimized BLW tuning rate. This succeeds in coordinately considering both chattering reduction and high-precision control realization in SMVSC.展开更多
基金supported by the National Natural Science Foundation of China(No.91844301)by the Beijing Municipal Natural Science Fund(No.JQ21030)。
文摘The coordinated control of PM_(2.5)and ozone has become the strategic goal of national air pollution control.Considering the gradual decline in PM_(2.5)concentration and the aggravation of ozone pollution,a better understanding of the coordinated control of PM_(2.5)and ozone is urgently needed.Here,we collected and sorted air pollutant data for 337 cities from 2015 to 2020 to explore the characteristics of PM_(2.5)and ozone pollution based on China’s five major air pollution regions.The results show that it is necessary to continue to strengthen the emission reduction in PM_(2.5)and ozone precursors,and control NO_(x) and VOCs while promoting a dramatic emission reduction in PM_(2.5).The primary method of curbing ozone pollution is to strengthen the emission control of VOCs,with a long-term strategy of achieving substantial emission reductions in NO_(x),because VOCs and NO_(x) are also precursors to PM_(2.5);hence,their reductions also contribute to the reduction in PM_(2.5).Therefore,the implementation of a multipollutant emission reduction control strategy aimed at the prevention and control of PM_(2.5)and ozone pollution is the only means to realize the coordinated control of PM_(2.5)and ozone.
基金This work was financially supported by the National Key Research and Development Program(2017YFF0211801)the National Natural Science Fund for Innovative Research Groups(51621003).
文摘The evaluation of the efficiency and feasibility of energy transition and air pollution control at the city level is one of the key points in addressing environmental problems and achieving the goals of CO_(2) emission reduction and carbon neutrality in China. In this study, an integrated method is developed on the basis of the Low Emissions Analysis Platform (LEAP) and life cycle assessment (LCA). The energy demands and environmental co-benefits in Jinan, one of the low-carbon city pilots in China, are quantitatively evaluated under three policy scenarios: low-carbon (LC) policy scenario, pollution control (PC) policy scenario, and deep-level cut of CO_(2) emissions (DCC) scenario from 2016 to 2050. From 2016 to 2030, the PC policies would be more powerful than the LC policies in terms of energy demand decrease. From 2030 to 2050, the LC policies would be more efficient than all the other policies. Promoting energy-saving buildings in the LC scenario would contribute to the continual decline in energy demands. In the DCC scenario, CO_(2), PM_(2.5), PM_(10), CO, NO_(X) and SO_(2) emissions would decline by more than 71.4% relative to the records in 2016. Global warming potential, human toxicity potential, photochemical ozone creation potential, particulate matter formation potential, and acidification potential would also decrease by 81.8%–88.5%. On the basis of the integrated city-level LEAP and LCA method, this study quantifies the various environmental impacts of urban decarbonization policies and provides science-based references for urban low-carbon transformation.
基金We thank the National Key R＆D Program of China （Grant 2016YFA0300404, X.W.） and the National Natural Science Foundation of China （Grants 21525102, 21690062, X.W. and 21601082, G.T.） for financial support. Dr. Li Zhang is acknowledged for proofreading the manuscript.
文摘Synthesis of stable main-group element-based radicals represents one of the most interesting topics in contemporary organometallic chem- istry, because of their vital roles in organic, inorganic and biological chemistry as well as materials science. However, the access of stable main-group element-based radicals is highly challenging owing to the lack of energetically accessible orbitals in the main-group elements. During the last decades, several synthetic strategies have been developed in obtaining these reactive species. Among them, utilizing the stericaliy demanding substituents and x-conjugated ligands has proven to be an effective approach. Weakly coordinating ions （WCAs） have also been found to be exceptionally practical in synthesizing radical cations of main-group elements. By introducing these stabilization methods, we have successfully prepared a variety of radical ions of p-block elements in the crystalline forms, and investigated their properties by different experimental and quantum chemical calculation methods. According to the investigations, magnetic stability was observed, resulting from the intramolecular electron-exchange interaction. Furthermore, we also found that the singlet-triptet energy gaps of the bis（triarylamine） diradical dications can be tunable by varying the temperature. These investigations open new avenues of the main-group element-based radicals for a large variety of applications.
基金supported by the National Key Research and Development Program of China(2022YFB3807500)the Natural Science Foundation of China(22220102003)+3 种基金the Beijing Natural Science Foundation(JL23003)"Double-First-Class"construction projects(XK180301 and XK1804-02)China Postdoctoral Science Foundation 2023TQ0020Dostdoctoral Fellowship Program of CPSF(GZC20230199)。
文摘The implementation of pristine covalent organic polymer(CO_(2)P)with well-defined structure as air electrode may spark fresh vitality to rechargeable zinc-air flow batteries(ZAFBs),but it still remains challenges in synergistically regulating their electronic states and structural porosity for the great device performance.Here,we conquer these issues by exploiting N and S co-doped graphene with COP rich in metal-ligand nitrogen to synergistically construct an effective catalyst for oxygen reduction reaction(ORR).Among them,the N and S co-doped sites with high electronegativity properties alter the number of electron occupations in the d orbital of the iron centre and form electron-transfer bridges,thereby boosting the selectivity of the ORR-catalysed four-electron pathway.Meanwhile,the introduction of COP materials aids the formation of pore interstices in the graphene lamellae,which both adequately expose the active sites and facilitate the transport of reactive substances.Benefiting from the synergistic effect,as-prepared catalyst exhibits excellent half-wave potentials(E_(1/2)=912 mV)and stability(merely 8.8%drop after a long-term durability test of 50000 s).Further,ZAFBs assembled with the N/SG@CO_(2)P catalyst demonstrate exceptional power density(163.8 mW cm^(-2))and continuous charge and discharge for approximately 140 h at 10 mA cm^(-2),outperforming the noble-metal benchmarks.
文摘Walking is a complex task which includes hundreds of muscles, bones and joints working together to deliver smooth movements. With the complexity, walking has been widely investigated in order to identify the pattern of multi-segment movement and reveal the control mechanism. The degree of freedom and dimensional properties provide a view of the coordinative structure during walking, which has been extensively studied by using dimension reduction technique. In this paper, the studies related to the coordinative structure, dimensions detection and pattern reorganization during walking have been reviewed. Principal component analysis, as a popular technique, is widely used in the processing of human movement data. Both the principle and the outcomes of principal component analysis were introduced in this paper. This technique has been reported to successfully reduce the redundancy within the original data, identify the physical meaning represented by the extracted principal components and discriminate the different patterns. The coordinative structure during walking assessed by this technique could provide further information of the body control mechanism and correlate walking pattern with injury.
基金This work was supported by the Provincial Natural Science Foundation of Hunan(No.04JJ6033) the Research Foundation of Hunan Education Bureau (No.03C066).
文摘A sliding mode variable structure control （SMVSC） based on a coordinating optimization algorithm has been developed. Steady state error and control switching frequency are used to constitute the system performance indexes in the coordinating optimization, while the tuning rate of boundary layer width （BLW） is employed as the optimization parameter. Based on the mathematical relationship between the BLW and steady-state error, an optimized BLW tuning rate is added to the nonlinear control term of SMVSC. Simulation experiment results applied to the positioning control of an electro-hydraulic servo system show the comprehensive superiority in dynamical and static state performance by using the proposed controller is better than that by using SMVSC without optimized BLW tuning rate. This succeeds in coordinately considering both chattering reduction and high-precision control realization in SMVSC.
