Seawater zinc-air batteries are promising energy storage devices due to their high energy density and utilization of seawater electrolytes.However,their efficiency is hindered by the sluggish oxygen reduction reaction...Seawater zinc-air batteries are promising energy storage devices due to their high energy density and utilization of seawater electrolytes.However,their efficiency is hindered by the sluggish oxygen reduction reaction(ORR)and chlorideinduced degradation over conventional catalysts.In this study,we proposed a universal synthetic strategy to construct heteroatom axially coordinated Fe–N_(4) single-atom seawater catalyst materials(Cl–Fe–N_(4) and S–Fe–N_(4)).X-ray absorption spectroscopy confirmed their five-coordinated square pyramidal structure.Systematic evaluation of catalytic activities revealed that compared with S–Fe–N_(4),Cl–Fe–N_(4) exhibits smaller electrochemical active surface area and specific surface area,yet demonstrates higher limiting current density(5.8 mA cm^(−2)).The assembled zinc-air batteries using Cl–Fe–N_(4) showed superior power density(187.7 mW cm^(−2) at 245.1 mA cm^(−2)),indicating that Cl axial coordination more effectively enhances the intrinsic ORR activity.Moreover,Cl–Fe–N_(4) demonstrates stronger Cl−poisoning resistance in seawater environments.Chronoamperometry tests and zinc-air battery cycling performance evaluations confirmed its enhanced stability.Density functional theory calculations revealed that the introduction of heteroatoms in the axial direction regulates the electron center of Fe single atom,leading to more active reaction intermediates and increased electron density of Fe single sites,thereby enhancing the reduction in adsorbed intermediates and hence the overall ORR catalytic activity.展开更多
Coronavirus disease 2019(COVID-19)has become a worldwide pandemic.Hospitalized patients of COVID-19 suffer from a high mortality rate,motivating the development of convenient and practical methods that allow clinician...Coronavirus disease 2019(COVID-19)has become a worldwide pandemic.Hospitalized patients of COVID-19 suffer from a high mortality rate,motivating the development of convenient and practical methods that allow clinicians to promptly identify high-risk patients.Here,we have developed a risk score using clinical data from 1479 inpatients admitted to Tongji Hospital,Wuhan,China(development cohort)and externally validated with data from two other centers:141 inpatients from Jinyintan Hospital,Wuhan,China(validation cohort 1)and 432 inpatients from The Third People’s Hospital of Shenzhen,Shenzhen,China(validation cohort 2).The risk score is based on three biomarkers that are readily available in routine blood samples and can easily be translated into a probability of death.The risk score can predict the mortality of individual patients more than 12 d in advance with more than 90%accuracy across all cohorts.Moreover,the Kaplan-Meier score shows that patients can be clearly differentiated upon admission as low,intermediate,or high risk,with an area under the curve(AUC)score of 0.9551.In summary,a simple risk score has been validated to predict death in patients infected with severe acute respiratory syndrome coronavirus 2(SARS-CoV-2);it has also been validated in independent cohorts.展开更多
Seed watermelon kernel is a typical complex food with high fat and protein contents.During storage and processing,it is often affected by various factors to undergo interactions between components,which lead to its qu...Seed watermelon kernel is a typical complex food with high fat and protein contents.During storage and processing,it is often affected by various factors to undergo interactions between components,which lead to its quality change.In this experiment,seed watermelon kernels were used as research objects,and the effects of 2-Azobis(2-amidinopropane)dihydrochloride(AAPH)on seed watermelon kernel protein isolates(WMP)were investigated.The structure and digestion characteristics of WMP after oxidation were studied.The results showed that with the increase of AAPH concentration(0.05−5 mol/L),WMP showed obvious aggregation,and its solubility decreased from 6.76 mg/mL to 9.59 mg/mL.The free sulfhydryl content of WMP was 18.24 mmol/g decreased to 11.25 mmol/g,α-helix decreased andβ-sheet decreased in secondary structure,and its disulfide bond increased by 43.06 mmol/g from 39.57 mmol/g,enthalpy(H)and denaturation temperature increased(Td)(P<0.05).By mass spectrometry results of simulated gastric digestion products,it was found that oxidation adversely affected the digestion characteristics of WMP.It can be seen that the lipid oxidation product APPH of seed watermelon kernel can significantly affect the structure and function of the protein extracted from the seed kernel.展开更多
The rapid miniaturization and a consequent increase in electromagnetic wave(EM)and heat emission in integrated electronic devices are now urgently desiring for multifunctional polymer composites that simultaneously po...The rapid miniaturization and a consequent increase in electromagnetic wave(EM)and heat emission in integrated electronic devices are now urgently desiring for multifunctional polymer composites that simultaneously possess high mechanical properties,excellent electromagnetic interference(EMI)shield-ing ability and heat dissipation capability.Herein,a series of novel polyimide-based composite films were constructed by rationally assembling the carbon nanofiber-grafted carbon fiber(NCF)and reduced graphene oxide(rGO)into a highly electrically and thermally conductive pathway within polyimide ma-trix via a sequential bidirectional freezing casting and hot-pressing strategy.The combination of high tensile strength and toughness was obtained by incorporating rGO into the NCF-reinforced PI composite,giving rise to a hierarchical reinforcing structure of NCF and crack deflection induced by rGO nanosheets.The high electrical conductivity(7.0×10^(3) S m^(-1))endows the PI/NCF30/rGO3.5 composite film with a good EMI shielding effectiveness of 45 dB.Moreover,the well-aligned thermally conductive NCF and rGO and strong interfacial bonding between the polymer matrix and reinforcing fibers give rise to improved thermal conductivity(λ),particularly along the in-plane direction.Typically,the PI/NCF30/rGO3.5 exhibits an in-plane thermal conductivity of 5.18 W m^(-1) K^(-1),∼4.7 times increment compared to the pure PI(0.91 W m^(-1) K^(-1)).Besides,the resultant PI/NCF30/rGO3.5 composite film presents a superior Joule heat-ing performance with some features of fast thermal response,ease of regulation and sufficient reliability.Accordingly,the developed multifunctional polyimide-based composite films demonstrate high potential as advanced EMI shielding materials with excellent heat dissipation.展开更多
High-performance polymer-based aerogel fibers with ultrahigh porosity,mechanical robustness and outstanding thermal stability are demanded for applying in effective thermal insulation devices,especially in harsh envir...High-performance polymer-based aerogel fibers with ultrahigh porosity,mechanical robustness and outstanding thermal stability are demanded for applying in effective thermal insulation devices,especially in harsh environment.However,the poor mechanical properties and thermal stability of the commonly reported polymer-based aerogel fibers restricted their applications in many areas.As a special nano-build-block,aramid nanofiber-based aerogel fiber is expected to conquer this problem in virtue of the outstanding performance,intrinsically related to aramid fibers.Herein,a series of aramid nanofiber-based aerogel fibers were fabricated via a facial wet-spinning method combined with freeze-drying technique.The effects of coagulation bath temperature and the solid contents of the spinning precursors on their morphologies and mechanical properties were systematically studied.The obtained aerogel fibers possessed high porosity(>92%),good mechanical prop-erties(tensile strength~8.1 MPa)and high specific surface area(~239 m^(2)/g).Meanwhile,the woven textiles exhibited a low thermal conductivity(~34 mW/(m·K))and outstanding thermal insulation properties under a wide range of temperature.In addition,surface modification by Teflon resin could make the ANAFs hydrophobic,thus exhibiting their applicational pros-pects in a humid environment.Overall,the aramid nanofiber-based aerogel fibers and their textile throw light in a favorable direction for developing high-performance thermal insulation fibers and textiles.展开更多
Despite tremendous effort,continuous fabrication of high-performance conductive polymer fibers for electromagnetic interference(EMI)shielding applications remains a daunting technical challenge.In the current study,we...Despite tremendous effort,continuous fabrication of high-performance conductive polymer fibers for electromagnetic interference(EMI)shielding applications remains a daunting technical challenge.In the current study,we report an efficient strategy for continuous surface metallization of polyimide fibers used in textile-substrate electromagnetic shielding applications.Polyimide fibers with pendent carboxyl groups(PIC)were first fabricated,and a conductive nickel layer was continuously coated on the PIC surface by electroless metal deposition(ELD).The carboxyl groups introduced onto the fiber surface acted as binding sites for the Ni^(2+)ions,and the complexation reactions greatly increased the Ni^(2+)adsorption capacity and efficiency of the PIC fibers during the ELD process and ensured continuous fabrication.Through judicious control of the plating time,a series of nickel-layer-coated PIC fibers(Ni-PIC)were constructed with Ni loadings ranging from 20 to 230 wt%.The resultant Ni-PIC fiber containing 65 wt%Ni exhibited conductivity of 223 S cm^(−1),and the corresponding fabric exhibited an EMI shielding effectiveness(EMI SE)of 44 dB in the X-band.The corresponding EMI SE was further improved to 83 dB after the fiber was treated at 300℃ for 1 h because of the crystallization of the Ni layer.The prepared Ni-PIC fibers and fabrics were also used in pressure sensors and electrothermal conversion,which demonstrated outstanding adaptabilities to various temperatures and mechanical properties.Overall,this work provides an efficient route for developing high-performance conductive polyimide fibers for EMI shielding applications,especially for use in military and aerospace equipment and in other harsh environments.展开更多
In recent years,China has witnessed the rapid development in housing finance,and there have emerged constantly real estate finance innovations;however,there exists no relevant index for measuring the innovations of Ch...In recent years,China has witnessed the rapid development in housing finance,and there have emerged constantly real estate finance innovations;however,there exists no relevant index for measuring the innovations of China's real estate finance.Based on the perspectives of the governments,enterprises and the public,this paper constructs the"innovation index of real estate finance"on a quarterly basis from 2009 to 2019,with the method of empowerment which combines the subjective method(analytic hierarchy process)and the objective one(range coefficient method).It clearly and concretely depicts the innovations in housing finance and the related temporal-spatial characteristics in China since the outbreak of the financial crisis in 2008.The index covers 30 provinces,autonomous regions and municipalities directly under the central government,and analyzes its temporal and spatial characteristics.The findings show that there exist a strong spatial autocorrelation and a big regional difference in innovations.展开更多
China’s grain science and technology policies have played an important role in the development of China’s food industry.This paper aims to examine the effects of China’s grain science and technology policies on foo...China’s grain science and technology policies have played an important role in the development of China’s food industry.This paper aims to examine the effects of China’s grain science and technology policies on food security.It quantitatively assesses China’s food security by analyzing the main contents and development trends of China’s food science technology policies through the text metrology method,and then investigates the effects of grain science and technology policies on food security by employing a provincial dynamic panel model.The results show that food security in China is all-round developed,and that the release frequency and cumulative effect of grain science and technology policies play a significant role in promoting food security.Powerful grain science and technology policies can effectively guarantee China’s food security.展开更多
Rational construction of active components has been the biggest challenge in preparing efficient bifunctional oxygen electrocatalysts.Herein,electrospinning and chemical vapor deposition(CVD)were employed to embed act...Rational construction of active components has been the biggest challenge in preparing efficient bifunctional oxygen electrocatalysts.Herein,electrospinning and chemical vapor deposition(CVD)were employed to embed active species including FeCo nanoparticles,MNx(M=Fe,Co),and FePx in porous and graphitized carbon nanotubes(CNTs)/carbon nanofiber(CNF).The as-prepared FeCo@CoNx@FePx/C exhibited a half-wave potential as high as 0.86 V in oxygen reduction reaction(ORR)and low oxygen evolution reaction(OER)overpotential of 368 mV at 10 mA·cm^(−2),which are superior to Pt/C(0.83 V)and IrO_(2)(375 mV)respectively.The assembled Zn-air battery(ZAB)showed a high energy efficiency(Edischarge/Echarge)of 65%at 20 mA·cm^(−2)and stabilized for 700 charge-discharge cycles.The spectroscopic and microscopic characterizations evidenced that the outstanding bifunctionality of the electrocatalyst can be ascribed to three main reasons:First,FeCo nanoparticles are rich in MOH/MOOH active sites for OER,and FePx/CNTs constructed with CVD also modulate electronic structure to improve electron transfer;second,both MNx in carbon matrix and FePx/CNTs are highly active towards ORR;third,the CNTs/CNF are highly porous and graphitized,which promotes mass transport and improves electrical conductivity and stability of the electrocatalysts.This work gives important implications on the design of bifunctional electrocatalysts.展开更多
To improve the accuracy of photovoltaic power prediction,a combined prediction model integrating multiple algorithms is proposed.First,key factors are selected,and the Gaussian Mixture Model(GMM)is used to cluster and...To improve the accuracy of photovoltaic power prediction,a combined prediction model integrating multiple algorithms is proposed.First,key factors are selected,and the Gaussian Mixture Model(GMM)is used to cluster and generate historical days with high correlation to the forecast day.Then,a photovoltaic power prediction model based on Variational Mode Decomposition(VMD)and an improved Grey Wolf Optimizer Kernel Extreme Learning Machine(MSI-GWO-KELM)is constructed.Finally,actual data from a photovoltaic power station in Australia is used as a case study.The results show that the VMD-MSI-GWOKELM model is suitable for different weather conditions and offers better prediction accuracy than other models.展开更多
Scholars have a variety of theoretical explanations for housing price growth. However, few scholars have studied the internal influence mechanism among urbanization, land finance, and housing price. Based on the data ...Scholars have a variety of theoretical explanations for housing price growth. However, few scholars have studied the internal influence mechanism among urbanization, land finance, and housing price. Based on the data of 182 prefecture-level cities from 2009 to 2016, this paper studies the influence of land finance on housing price under different urbanization rate levels. The study finds that with the increase of urbanization rate, the effect of land finance on housing price presents a "U" shape.Specifically, an increase in land finance by 1% results in a corresponding increase in average housing price by 0.18%, with relatively low urbanization rate, 0.06% with medium level of urbanization rate,and 0.38% with high level of urbanization rate.展开更多
Reduction of carbon dioxide(CO2)emissions is one of the biggest challenges for global sustainable development,in which economic growth characterized by industrialization plays a formidable role.We innovatively adopted...Reduction of carbon dioxide(CO2)emissions is one of the biggest challenges for global sustainable development,in which economic growth characterized by industrialization plays a formidable role.We innovatively adopted the input and output(I-O)table of 41 countries released by World I-O Database to determine the industrial structure change and analyze its impact on CO2 emission evolution by developing a cross-country panel model.The empirical results show that industrial structure change has a significantly negative effect on CO2 emissions;to be specific,0.1 unit increase in the linkage of manufacturing sector and service sector will lead to a decrease of 0.94 metric tons per capita CO2 emissions,indicating that upgrading industrial structure contributes to carbon mitigation and sustainable development.Further,urbanization,technology and trade openness have significantly negative impact on CO2 emissions,while economy growth and energy use take positive impacts.In particular,a 1%increase in per capita income will contribute to an increase of 8.6 metric tons per capita CO2 emissions.However,the effect of industrial structure on environment degradation is moderated by technology level.These findings fill the gaps of previous literature and provide valuable references for effective policies to mitigate CO2 emissions and achieve sustainable development.展开更多
House price expectations(HPE)is a key factor affecting housing market fluctuations.Taking Beijing as an example,this study innovatively proposes an internet data-based measurement of HPE and text analysis-based quanti...House price expectations(HPE)is a key factor affecting housing market fluctuations.Taking Beijing as an example,this study innovatively proposes an internet data-based measurement of HPE and text analysis-based quantification of media reports from media attention and media attitudes.Regression model is performed to empirically test the impact of media reports on the level and accuracy of HPE.The empirical results show no significant relationship between media attention and the level of HPE,but a significant relationship to the accuracy of HPE.The higher the media attention(i.e.,the more intensive the media reports),the smaller the deviation between HPE and actual housing prices.The attitude of media reports is significantly related to the level and accuracy of HPE.It is easier to guide the formation of HPE through media reports with clear opinions,indicating that media could promote the sustainable development of the real estate market.展开更多
基金funded by the Innovative Research Group Project of the National Natural Science Foundation of China(52121004)the Research Development Fund(No.RDF-21-02-060)by Xi’an Jiaotong-Liverpool University+1 种基金support received from the Suzhou Industrial Park High Quality Innovation Platform of Functional Molecular Materials and Devices(YZCXPT2023105)the XJTLU Advanced Materials Research Center(AMRC).
文摘Seawater zinc-air batteries are promising energy storage devices due to their high energy density and utilization of seawater electrolytes.However,their efficiency is hindered by the sluggish oxygen reduction reaction(ORR)and chlorideinduced degradation over conventional catalysts.In this study,we proposed a universal synthetic strategy to construct heteroatom axially coordinated Fe–N_(4) single-atom seawater catalyst materials(Cl–Fe–N_(4) and S–Fe–N_(4)).X-ray absorption spectroscopy confirmed their five-coordinated square pyramidal structure.Systematic evaluation of catalytic activities revealed that compared with S–Fe–N_(4),Cl–Fe–N_(4) exhibits smaller electrochemical active surface area and specific surface area,yet demonstrates higher limiting current density(5.8 mA cm^(−2)).The assembled zinc-air batteries using Cl–Fe–N_(4) showed superior power density(187.7 mW cm^(−2) at 245.1 mA cm^(−2)),indicating that Cl axial coordination more effectively enhances the intrinsic ORR activity.Moreover,Cl–Fe–N_(4) demonstrates stronger Cl−poisoning resistance in seawater environments.Chronoamperometry tests and zinc-air battery cycling performance evaluations confirmed its enhanced stability.Density functional theory calculations revealed that the introduction of heteroatoms in the axial direction regulates the electron center of Fe single atom,leading to more active reaction intermediates and increased electron density of Fe single sites,thereby enhancing the reduction in adsorbed intermediates and hence the overall ORR catalytic activity.
基金supported by the Special Fund for Novel Coronavirus Pneumonia from the Department of Science and Technology of Hubei Province(2020FCA035)the Fundamental Research Funds for the Central Universities,Huazhong University of Science and Technology(2020kfyXGYJ023).
文摘Coronavirus disease 2019(COVID-19)has become a worldwide pandemic.Hospitalized patients of COVID-19 suffer from a high mortality rate,motivating the development of convenient and practical methods that allow clinicians to promptly identify high-risk patients.Here,we have developed a risk score using clinical data from 1479 inpatients admitted to Tongji Hospital,Wuhan,China(development cohort)and externally validated with data from two other centers:141 inpatients from Jinyintan Hospital,Wuhan,China(validation cohort 1)and 432 inpatients from The Third People’s Hospital of Shenzhen,Shenzhen,China(validation cohort 2).The risk score is based on three biomarkers that are readily available in routine blood samples and can easily be translated into a probability of death.The risk score can predict the mortality of individual patients more than 12 d in advance with more than 90%accuracy across all cohorts.Moreover,the Kaplan-Meier score shows that patients can be clearly differentiated upon admission as low,intermediate,or high risk,with an area under the curve(AUC)score of 0.9551.In summary,a simple risk score has been validated to predict death in patients infected with severe acute respiratory syndrome coronavirus 2(SARS-CoV-2);it has also been validated in independent cohorts.
基金This study was supported by National Natural Science Foundation of China(No:31760477)Beijing Advanced Innovation Center for Food Nutrition and Human Health(No:20181007)Youth Science and Technology Innovation,Leader in Corps(No:2016BC001).
文摘Seed watermelon kernel is a typical complex food with high fat and protein contents.During storage and processing,it is often affected by various factors to undergo interactions between components,which lead to its quality change.In this experiment,seed watermelon kernels were used as research objects,and the effects of 2-Azobis(2-amidinopropane)dihydrochloride(AAPH)on seed watermelon kernel protein isolates(WMP)were investigated.The structure and digestion characteristics of WMP after oxidation were studied.The results showed that with the increase of AAPH concentration(0.05−5 mol/L),WMP showed obvious aggregation,and its solubility decreased from 6.76 mg/mL to 9.59 mg/mL.The free sulfhydryl content of WMP was 18.24 mmol/g decreased to 11.25 mmol/g,α-helix decreased andβ-sheet decreased in secondary structure,and its disulfide bond increased by 43.06 mmol/g from 39.57 mmol/g,enthalpy(H)and denaturation temperature increased(Td)(P<0.05).By mass spectrometry results of simulated gastric digestion products,it was found that oxidation adversely affected the digestion characteristics of WMP.It can be seen that the lipid oxidation product APPH of seed watermelon kernel can significantly affect the structure and function of the protein extracted from the seed kernel.
基金financially supported by the National Natu-ral Science Foundation of China(Nos.51903038,52173196 and 21975040)the Scientific Research Innovation Plan of Shanghai Ed-ucation Commission(No.2019-01-07-00-03-E00001)+1 种基金the Natural Science Foundation of Shanghai(No.21ZR1400200)the Na-tional Innovation and Entrepreneurship Training program for Col-lege students in Henan Province(No.202110480010).
文摘The rapid miniaturization and a consequent increase in electromagnetic wave(EM)and heat emission in integrated electronic devices are now urgently desiring for multifunctional polymer composites that simultaneously possess high mechanical properties,excellent electromagnetic interference(EMI)shield-ing ability and heat dissipation capability.Herein,a series of novel polyimide-based composite films were constructed by rationally assembling the carbon nanofiber-grafted carbon fiber(NCF)and reduced graphene oxide(rGO)into a highly electrically and thermally conductive pathway within polyimide ma-trix via a sequential bidirectional freezing casting and hot-pressing strategy.The combination of high tensile strength and toughness was obtained by incorporating rGO into the NCF-reinforced PI composite,giving rise to a hierarchical reinforcing structure of NCF and crack deflection induced by rGO nanosheets.The high electrical conductivity(7.0×10^(3) S m^(-1))endows the PI/NCF30/rGO3.5 composite film with a good EMI shielding effectiveness of 45 dB.Moreover,the well-aligned thermally conductive NCF and rGO and strong interfacial bonding between the polymer matrix and reinforcing fibers give rise to improved thermal conductivity(λ),particularly along the in-plane direction.Typically,the PI/NCF30/rGO3.5 exhibits an in-plane thermal conductivity of 5.18 W m^(-1) K^(-1),∼4.7 times increment compared to the pure PI(0.91 W m^(-1) K^(-1)).Besides,the resultant PI/NCF30/rGO3.5 composite film presents a superior Joule heat-ing performance with some features of fast thermal response,ease of regulation and sufficient reliability.Accordingly,the developed multifunctional polyimide-based composite films demonstrate high potential as advanced EMI shielding materials with excellent heat dissipation.
基金supported by the National Natural Science Foundation of China(NSFC)(21975040)the Scientific Research Innovation Plan of Shanghai Education Commission(2019-01-07-00-03-E00001)the Fundamental Research Funds for the Central Universities and the Graduate Student Innovation Fund of Donghua University(CUSF-DH-D-2021007).
文摘High-performance polymer-based aerogel fibers with ultrahigh porosity,mechanical robustness and outstanding thermal stability are demanded for applying in effective thermal insulation devices,especially in harsh environment.However,the poor mechanical properties and thermal stability of the commonly reported polymer-based aerogel fibers restricted their applications in many areas.As a special nano-build-block,aramid nanofiber-based aerogel fiber is expected to conquer this problem in virtue of the outstanding performance,intrinsically related to aramid fibers.Herein,a series of aramid nanofiber-based aerogel fibers were fabricated via a facial wet-spinning method combined with freeze-drying technique.The effects of coagulation bath temperature and the solid contents of the spinning precursors on their morphologies and mechanical properties were systematically studied.The obtained aerogel fibers possessed high porosity(>92%),good mechanical prop-erties(tensile strength~8.1 MPa)and high specific surface area(~239 m^(2)/g).Meanwhile,the woven textiles exhibited a low thermal conductivity(~34 mW/(m·K))and outstanding thermal insulation properties under a wide range of temperature.In addition,surface modification by Teflon resin could make the ANAFs hydrophobic,thus exhibiting their applicational pros-pects in a humid environment.Overall,the aramid nanofiber-based aerogel fibers and their textile throw light in a favorable direction for developing high-performance thermal insulation fibers and textiles.
基金the Scientific Research Innovation Plan of Shanghai Education Commission(2019-01-07-00-03-E00001)National Natural Science Foundation of China(No.U21A2087,21975040)the Natural Science Foundation of Shanghai(21ZR1400200).
文摘Despite tremendous effort,continuous fabrication of high-performance conductive polymer fibers for electromagnetic interference(EMI)shielding applications remains a daunting technical challenge.In the current study,we report an efficient strategy for continuous surface metallization of polyimide fibers used in textile-substrate electromagnetic shielding applications.Polyimide fibers with pendent carboxyl groups(PIC)were first fabricated,and a conductive nickel layer was continuously coated on the PIC surface by electroless metal deposition(ELD).The carboxyl groups introduced onto the fiber surface acted as binding sites for the Ni^(2+)ions,and the complexation reactions greatly increased the Ni^(2+)adsorption capacity and efficiency of the PIC fibers during the ELD process and ensured continuous fabrication.Through judicious control of the plating time,a series of nickel-layer-coated PIC fibers(Ni-PIC)were constructed with Ni loadings ranging from 20 to 230 wt%.The resultant Ni-PIC fiber containing 65 wt%Ni exhibited conductivity of 223 S cm^(−1),and the corresponding fabric exhibited an EMI shielding effectiveness(EMI SE)of 44 dB in the X-band.The corresponding EMI SE was further improved to 83 dB after the fiber was treated at 300℃ for 1 h because of the crystallization of the Ni layer.The prepared Ni-PIC fibers and fabrics were also used in pressure sensors and electrothermal conversion,which demonstrated outstanding adaptabilities to various temperatures and mechanical properties.Overall,this work provides an efficient route for developing high-performance conductive polyimide fibers for EMI shielding applications,especially for use in military and aerospace equipment and in other harsh environments.
基金Supported by the National Science Foundation of China (71850014,71974108)Research on the Scientific and Technological Support Measures to Ensure Financial Security (2020-ZW10-A-022)R&D Program of China Construction Second Engineering Bureau Ltd (2021ZX190001)。
文摘In recent years,China has witnessed the rapid development in housing finance,and there have emerged constantly real estate finance innovations;however,there exists no relevant index for measuring the innovations of China's real estate finance.Based on the perspectives of the governments,enterprises and the public,this paper constructs the"innovation index of real estate finance"on a quarterly basis from 2009 to 2019,with the method of empowerment which combines the subjective method(analytic hierarchy process)and the objective one(range coefficient method).It clearly and concretely depicts the innovations in housing finance and the related temporal-spatial characteristics in China since the outbreak of the financial crisis in 2008.The index covers 30 provinces,autonomous regions and municipalities directly under the central government,and analyzes its temporal and spatial characteristics.The findings show that there exist a strong spatial autocorrelation and a big regional difference in innovations.
基金Supported by Chinese Academy of Sciences(KJZD-EW-G20)the National Natural Science Foundation of China(71974180)
文摘China’s grain science and technology policies have played an important role in the development of China’s food industry.This paper aims to examine the effects of China’s grain science and technology policies on food security.It quantitatively assesses China’s food security by analyzing the main contents and development trends of China’s food science technology policies through the text metrology method,and then investigates the effects of grain science and technology policies on food security by employing a provincial dynamic panel model.The results show that food security in China is all-round developed,and that the release frequency and cumulative effect of grain science and technology policies play a significant role in promoting food security.Powerful grain science and technology policies can effectively guarantee China’s food security.
基金the grants from the National Natural Science Foundation of China(No.22004085)Regional Joint Fund of Guangdong Province(No.2019A1515111054).
文摘Rational construction of active components has been the biggest challenge in preparing efficient bifunctional oxygen electrocatalysts.Herein,electrospinning and chemical vapor deposition(CVD)were employed to embed active species including FeCo nanoparticles,MNx(M=Fe,Co),and FePx in porous and graphitized carbon nanotubes(CNTs)/carbon nanofiber(CNF).The as-prepared FeCo@CoNx@FePx/C exhibited a half-wave potential as high as 0.86 V in oxygen reduction reaction(ORR)and low oxygen evolution reaction(OER)overpotential of 368 mV at 10 mA·cm^(−2),which are superior to Pt/C(0.83 V)and IrO_(2)(375 mV)respectively.The assembled Zn-air battery(ZAB)showed a high energy efficiency(Edischarge/Echarge)of 65%at 20 mA·cm^(−2)and stabilized for 700 charge-discharge cycles.The spectroscopic and microscopic characterizations evidenced that the outstanding bifunctionality of the electrocatalyst can be ascribed to three main reasons:First,FeCo nanoparticles are rich in MOH/MOOH active sites for OER,and FePx/CNTs constructed with CVD also modulate electronic structure to improve electron transfer;second,both MNx in carbon matrix and FePx/CNTs are highly active towards ORR;third,the CNTs/CNF are highly porous and graphitized,which promotes mass transport and improves electrical conductivity and stability of the electrocatalysts.This work gives important implications on the design of bifunctional electrocatalysts.
文摘To improve the accuracy of photovoltaic power prediction,a combined prediction model integrating multiple algorithms is proposed.First,key factors are selected,and the Gaussian Mixture Model(GMM)is used to cluster and generate historical days with high correlation to the forecast day.Then,a photovoltaic power prediction model based on Variational Mode Decomposition(VMD)and an improved Grey Wolf Optimizer Kernel Extreme Learning Machine(MSI-GWO-KELM)is constructed.Finally,actual data from a photovoltaic power station in Australia is used as a case study.The results show that the VMD-MSI-GWOKELM model is suitable for different weather conditions and offers better prediction accuracy than other models.
基金Supported by Natural Science Foundation of China(71850014,71532013,71573244,71974180)。
文摘Scholars have a variety of theoretical explanations for housing price growth. However, few scholars have studied the internal influence mechanism among urbanization, land finance, and housing price. Based on the data of 182 prefecture-level cities from 2009 to 2016, this paper studies the influence of land finance on housing price under different urbanization rate levels. The study finds that with the increase of urbanization rate, the effect of land finance on housing price presents a "U" shape.Specifically, an increase in land finance by 1% results in a corresponding increase in average housing price by 0.18%, with relatively low urbanization rate, 0.06% with medium level of urbanization rate,and 0.38% with high level of urbanization rate.
基金Supported by the National Natural Science Foundation of China(71403260,71573244,71532013).
文摘Reduction of carbon dioxide(CO2)emissions is one of the biggest challenges for global sustainable development,in which economic growth characterized by industrialization plays a formidable role.We innovatively adopted the input and output(I-O)table of 41 countries released by World I-O Database to determine the industrial structure change and analyze its impact on CO2 emission evolution by developing a cross-country panel model.The empirical results show that industrial structure change has a significantly negative effect on CO2 emissions;to be specific,0.1 unit increase in the linkage of manufacturing sector and service sector will lead to a decrease of 0.94 metric tons per capita CO2 emissions,indicating that upgrading industrial structure contributes to carbon mitigation and sustainable development.Further,urbanization,technology and trade openness have significantly negative impact on CO2 emissions,while economy growth and energy use take positive impacts.In particular,a 1%increase in per capita income will contribute to an increase of 8.6 metric tons per capita CO2 emissions.However,the effect of industrial structure on environment degradation is moderated by technology level.These findings fill the gaps of previous literature and provide valuable references for effective policies to mitigate CO2 emissions and achieve sustainable development.
基金Supported by the National Natural Science Foundation of China(71573244,71532013,71850014)
文摘House price expectations(HPE)is a key factor affecting housing market fluctuations.Taking Beijing as an example,this study innovatively proposes an internet data-based measurement of HPE and text analysis-based quantification of media reports from media attention and media attitudes.Regression model is performed to empirically test the impact of media reports on the level and accuracy of HPE.The empirical results show no significant relationship between media attention and the level of HPE,but a significant relationship to the accuracy of HPE.The higher the media attention(i.e.,the more intensive the media reports),the smaller the deviation between HPE and actual housing prices.The attitude of media reports is significantly related to the level and accuracy of HPE.It is easier to guide the formation of HPE through media reports with clear opinions,indicating that media could promote the sustainable development of the real estate market.
