Nitrogen-coordinated iron atoms on carbon supports(Fe-N-C)are among the most promising noble-metal-free electrocatalysts for oxygen reduction reaction(ORR).However,their unsatisfactory stability limits their prac-tica...Nitrogen-coordinated iron atoms on carbon supports(Fe-N-C)are among the most promising noble-metal-free electrocatalysts for oxygen reduction reaction(ORR).However,their unsatisfactory stability limits their prac-tical application.Herein,we demonstrate a dual-shell Fe-N-C electrocatalyst with excellent catalytic activity and long-term stability.Pyrrole and dopamine are sequentially polymerized on a fumed silica nanoparticle template.Metal precursor(FeCl_(3))and pore formation agent(ZnCl_(2))were loaded on the inner polypyrrole shell.During carbonization,the Zn evaporation creates abundant mesopores in the polydopamine-derived outer carbon shell,forming a "chain mail"like outer shell that protects Fe-N-C active sites loaded on the inner carbon shell and enables efficient mass transfer.Systematical tuning of the shield thickness and porosity affords the optimal electrocatalyst with a large surface area of 934 m^(2)g^(-1) and a high Fe loading of 2.04 wt%.This electrocatalyst delivers excellent ORR activity and superior stability in both acidic and alkaline electrolytes.Primary Zn-air batteries fabricated from this electrocatalyst delivers a high-power density of 257 mW cm^(-2) and impressive durability of continuous discharging over 250 h.Creating a graphitic and porous carbon protective shell can be further extended to other electrocatalysts to enable their practical applications in energy conversion and storage.展开更多
The source and load uncertainties arising from increased applications of renewable energy sources such as wind and photovoltaic energy in the power system have had adverse effects on optimal planning and dispatching.M...The source and load uncertainties arising from increased applications of renewable energy sources such as wind and photovoltaic energy in the power system have had adverse effects on optimal planning and dispatching.Models for generating typical renewable energy and load scenarios are constructed to reduce such effects and improve the applicability of a planning and optimal dispatching model of power systems with a high proportion of renewable energy.The traditional clustering-based model for representing such scenarios cannot handle high-dimensional time-series data and consequently the feature-related information obtained cannot fully reflect the characteristics of the data.Thus,a deep convolutional embedded clustering model based on multi-head self-attention is proposed.First,a variational mode decomposition model is optimized to reduce the influence of noise-related signals on the feature extraction.The deep features are then extracted from the data using an improved convolutional autoencoder,and the appropriate number of clusters is determined using the elbow method.Following this,the network parameters are optimized based on the sum of losses during reconstruction and clustering.Subsequently,typical scenarios are then generated based on the optimized network model.Finally,the proposed method is evaluated based on data visualization and evaluation metrics.It is shown that the quality of features and the accuracy of clustering can be effectively improved by the proposed scenario generation method.展开更多
In this review,we propose a comprehensive overview of additive manufacturing(AM)technologies and design possibilities in manufacturing metamaterials for various applications in the biomedical field,of which many are i...In this review,we propose a comprehensive overview of additive manufacturing(AM)technologies and design possibilities in manufacturing metamaterials for various applications in the biomedical field,of which many are inspired by nature itself.It describes how new AM technologies(e.g.continuous liquid interface production and multiphoton polymerization,etc)and recent developments in more mature AM technologies(e.g.powder bed fusion,stereolithography,and extrusion-based bioprinting(EBB),etc)lead to more precise,efficient,and personalized biomedical components.EBB is a revolutionary topic creating intricate models with remarkable mechanical compatibility of metamaterials,for instance,stress elimination for tissue engineering and regenerative medicine,negative or zero Poisson’s ratio.By exploiting the designs of porous structures(e.g.truss,triply periodic minimal surface,plant/animal-inspired,and functionally graded lattices,etc),AM-made bioactive bone implants,artificial tissues,and organs are made for tissue replacement.The material palette of the AM metamaterials has high diversity nowadays,ranging from alloys and metals(e.g.cobalt-chromium alloys and titanium,etc)to polymers(e.g.biodegradable polycaprolactone and polymethyl methacrylate,etc),which could be even integrated within bioactive ceramics.These advancements are driving the progress of the biomedical field,improving human health and quality of life.展开更多
Dear Editor,Colorectal cancer(CRC)is among the most commonly diagnosed cancer and the leading cause of cancer-related death worldwide[1].Most CRCs develop from adenomas.Laterally spreading tumors(LSTs)are non-polypoid...Dear Editor,Colorectal cancer(CRC)is among the most commonly diagnosed cancer and the leading cause of cancer-related death worldwide[1].Most CRCs develop from adenomas.Laterally spreading tumors(LSTs)are non-polypoid superficial colorectal neoplasms(CRNs)that are larger than 1 cm and typically extend laterally along the luminal wall.Based on surface morphology,it can be classified into a granular or nongranular type.The pathological morphology of LST manifests only as adenoma or with cancer.Recent studies have characterized 45-79%of LSTs as high-grade intraepithelial neoplasia(HGIN)or submucosal invasion;and the risk of submucosal invasion increases with lesion size[2].Hence,LST is considered a precancerous CRC lesion.Patients with LSTs are usually asymptomatic and diagnosis typically occurs during physical examinations or screening colonoscopy.展开更多
Exploring remarkable oxygen reduction reaction(ORR)electrocatalysts for regenerative fuel cells and metal-air batteries is highly essential.Herein,a novel non-noble metal-based heterogeneous electrocatalyst with rich ...Exploring remarkable oxygen reduction reaction(ORR)electrocatalysts for regenerative fuel cells and metal-air batteries is highly essential.Herein,a novel non-noble metal-based heterogeneous electrocatalyst with rich defects were successfully synthesized by liquid-liquid interfacial precipitation(LLIP)of fullerene(C_(60))and ferrotetraphenylporphyrin(FeTPP)followed by one step pyrolysis.The obtained product annealed at 700℃(C_(60)/FeTPP-700),when employed as ORR electrocatalyst,revealed a positive halfwave potential(E_(1/2))of 0.877 V vs.reversible hydrogen electrode(RHE),which was superior to that of the commercial 25%Pt/C.Delightfully,the assembled Zn-air battery(ZAB)using C_(60)/FeTPP-700 as an air-electrode catalyst exhibited a high power density of 153 m W/cm^(2),specific capacity of 668 mAh/g and long-term cycling stability for more than 250 h.Experimental results proved that the excellent electrocatalytic ORR activity of C_(60)/FeTPP-700 would attribute to the synergistic effect between FeN_xsites,Fe_(3)C/Fe nanoparticles and the structure defects.This work provides a feasible and simple method to prepare nonnoble metal-based ORR electrocatalysts for the application of energy storage and conversion.展开更多
Hydrogen evolution reaction(HER)and oxygen reduction reaction(ORR)have been considered as two critical processes in the field of electrocatalytic water-splitting for hydrogen production and fuel cells.However,the slug...Hydrogen evolution reaction(HER)and oxygen reduction reaction(ORR)have been considered as two critical processes in the field of electrocatalytic water-splitting for hydrogen production and fuel cells.However,the sluggish reaction kinetics of HER and ORR required efficient electrocatalyst such as Pt to promote such process.Transition metal phosphides(TMPs)exhibit great potential to replace noble metal electrocatalysts to accelerate HER and ORR due to their high activity and easy availability.Herein,a highly-efficient bifunctional CoP electrocatalyst for HER and ORR,featuring a unique core-shell structure decorated on nitrogen-doped carbon matrix was designed and constructed via etching a cobalt-based zeolitic imidazolate framework(ZIF-67)with phytic acid(PA)followed by pyrolysis treatment(PA-ZIF-67-900).Experimental results revealed that the pure-phase single-crystalline Co P exhibited outstanding electrocatalytic performance in HER and ORR,superior to Co(PO_(3))_(2) in PA-ZIF-67-700,hybrid phase of Co(PO_(3))_(2) and CoP in PA-ZIF-67-800 and Co_(2)P-doped CoP in PA-ZIF-67-1000.To reach the current density of 10 mA/cm^(2)the as-synthesized Co P required an overpotential of 120 m V for HER in 1 mol/L KOH and half-wave potential of 0.85 V in O_(2)-saturated 0.1 mol/L KOH.This work present new clue for construction of efficient and bifunctional electrocatalyst in the field of energy conversion and storage.展开更多
Multiple morphologies of colloidal perovskite nanocrystals(NCs)diversify their optical and electronic properties.Among them,the linear absorption cross-section(σ)is a primary parameter to determine their intrinsic ph...Multiple morphologies of colloidal perovskite nanocrystals(NCs)diversify their optical and electronic properties.Among them,the linear absorption cross-section(σ)is a primary parameter to determine their intrinsic photophysical features,and consequently,application potential.Herein,three morphologies of all-inorganic hybrid colloidal perovskite CsPbBr_(3)NCs,nanocubes(NBs),nanoplatelets(NLs),and nanowires(NWs),were targeted,and their linearσvalues were obtained through femtosecond transient absorption(TA)spectroscopy analysis.At high excitation energy well above the bandgap,theσper particle of all CsPbBr3 NCs linearly increased with the particle volume(VNC)regardless of the morphology with the value ofσ400=9.45×10^(4)cm^(−1)×VNC(cm^(2)).Density functional theory(DFT)calculation confirmed the negligible influence of shapes on the optical selection rules.The Einstein spontaneous emission coefficients calculated from theσvalues define the intrinsic radiative recombination rate.However,reduced size dependence is observed when the excitation energy is close to the bandgap(i.e.,at 460 nm)with the value ofσ460=2.82×10^(8)cm0.65×(VNC)0.45(cm^(2)).This should be ascribed to the discrete energy levels as well as lower density of states close to the band edge for perovskite NCs.These results provide in-depth insight into the optical characteristics for perovskite NCs.展开更多
基金the Australian Research Council under the Future Fellowships scheme(FT160100107)Discovery Programme(DP180102210)The University of Sydney under the Commercial Development and Industry Partnerships fund CDIP 332020.
文摘Nitrogen-coordinated iron atoms on carbon supports(Fe-N-C)are among the most promising noble-metal-free electrocatalysts for oxygen reduction reaction(ORR).However,their unsatisfactory stability limits their prac-tical application.Herein,we demonstrate a dual-shell Fe-N-C electrocatalyst with excellent catalytic activity and long-term stability.Pyrrole and dopamine are sequentially polymerized on a fumed silica nanoparticle template.Metal precursor(FeCl_(3))and pore formation agent(ZnCl_(2))were loaded on the inner polypyrrole shell.During carbonization,the Zn evaporation creates abundant mesopores in the polydopamine-derived outer carbon shell,forming a "chain mail"like outer shell that protects Fe-N-C active sites loaded on the inner carbon shell and enables efficient mass transfer.Systematical tuning of the shield thickness and porosity affords the optimal electrocatalyst with a large surface area of 934 m^(2)g^(-1) and a high Fe loading of 2.04 wt%.This electrocatalyst delivers excellent ORR activity and superior stability in both acidic and alkaline electrolytes.Primary Zn-air batteries fabricated from this electrocatalyst delivers a high-power density of 257 mW cm^(-2) and impressive durability of continuous discharging over 250 h.Creating a graphitic and porous carbon protective shell can be further extended to other electrocatalysts to enable their practical applications in energy conversion and storage.
基金supported by the Special Grant from the Department of Finance,Fujian Province(No.83022005)the National Natural Science Foundation of China(No.52107080).
文摘The source and load uncertainties arising from increased applications of renewable energy sources such as wind and photovoltaic energy in the power system have had adverse effects on optimal planning and dispatching.Models for generating typical renewable energy and load scenarios are constructed to reduce such effects and improve the applicability of a planning and optimal dispatching model of power systems with a high proportion of renewable energy.The traditional clustering-based model for representing such scenarios cannot handle high-dimensional time-series data and consequently the feature-related information obtained cannot fully reflect the characteristics of the data.Thus,a deep convolutional embedded clustering model based on multi-head self-attention is proposed.First,a variational mode decomposition model is optimized to reduce the influence of noise-related signals on the feature extraction.The deep features are then extracted from the data using an improved convolutional autoencoder,and the appropriate number of clusters is determined using the elbow method.Following this,the network parameters are optimized based on the sum of losses during reconstruction and clustering.Subsequently,typical scenarios are then generated based on the optimized network model.Finally,the proposed method is evaluated based on data visualization and evaluation metrics.It is shown that the quality of features and the accuracy of clustering can be effectively improved by the proposed scenario generation method.
基金sponsored by the Science and Technology Program of Hubei Province,China(2022EHB020,2023BBB096)support provided by Centre of the Excellence in Production Research(XPRES)at KTH。
文摘In this review,we propose a comprehensive overview of additive manufacturing(AM)technologies and design possibilities in manufacturing metamaterials for various applications in the biomedical field,of which many are inspired by nature itself.It describes how new AM technologies(e.g.continuous liquid interface production and multiphoton polymerization,etc)and recent developments in more mature AM technologies(e.g.powder bed fusion,stereolithography,and extrusion-based bioprinting(EBB),etc)lead to more precise,efficient,and personalized biomedical components.EBB is a revolutionary topic creating intricate models with remarkable mechanical compatibility of metamaterials,for instance,stress elimination for tissue engineering and regenerative medicine,negative or zero Poisson’s ratio.By exploiting the designs of porous structures(e.g.truss,triply periodic minimal surface,plant/animal-inspired,and functionally graded lattices,etc),AM-made bioactive bone implants,artificial tissues,and organs are made for tissue replacement.The material palette of the AM metamaterials has high diversity nowadays,ranging from alloys and metals(e.g.cobalt-chromium alloys and titanium,etc)to polymers(e.g.biodegradable polycaprolactone and polymethyl methacrylate,etc),which could be even integrated within bioactive ceramics.These advancements are driving the progress of the biomedical field,improving human health and quality of life.
基金This research was mainly supported by grants from the National Nature Science Funds of China(grant no.81772964),the Special Scientific Research Fund of Public Welfare Profession of National Health and Family Plan-ning Commission(grant no.201502026)and the Guang-dong Gastrointestinal Disease Research Center(grant no.2017B020209003).
文摘Dear Editor,Colorectal cancer(CRC)is among the most commonly diagnosed cancer and the leading cause of cancer-related death worldwide[1].Most CRCs develop from adenomas.Laterally spreading tumors(LSTs)are non-polypoid superficial colorectal neoplasms(CRNs)that are larger than 1 cm and typically extend laterally along the luminal wall.Based on surface morphology,it can be classified into a granular or nongranular type.The pathological morphology of LST manifests only as adenoma or with cancer.Recent studies have characterized 45-79%of LSTs as high-grade intraepithelial neoplasia(HGIN)or submucosal invasion;and the risk of submucosal invasion increases with lesion size[2].Hence,LST is considered a precancerous CRC lesion.Patients with LSTs are usually asymptomatic and diagnosis typically occurs during physical examinations or screening colonoscopy.
基金supported by the National Natural Science Foundation of China(Nos.52073166,52072226)the Key Program for International S&T Cooperation Projects of Shaanxi Province(Nos.2020KW-038,2020GHJD-04)+2 种基金Scientific Research Program Funded by Shaanxi Provincial Education Department(No.20JY001)Science and Technology Resource Sharing Platform of Shaanxi Province(No.2020PT-022)the support from the Science and Technology Youth Stars Project of Shaanxi Province(No.2021KJXX-35)。
文摘Exploring remarkable oxygen reduction reaction(ORR)electrocatalysts for regenerative fuel cells and metal-air batteries is highly essential.Herein,a novel non-noble metal-based heterogeneous electrocatalyst with rich defects were successfully synthesized by liquid-liquid interfacial precipitation(LLIP)of fullerene(C_(60))and ferrotetraphenylporphyrin(FeTPP)followed by one step pyrolysis.The obtained product annealed at 700℃(C_(60)/FeTPP-700),when employed as ORR electrocatalyst,revealed a positive halfwave potential(E_(1/2))of 0.877 V vs.reversible hydrogen electrode(RHE),which was superior to that of the commercial 25%Pt/C.Delightfully,the assembled Zn-air battery(ZAB)using C_(60)/FeTPP-700 as an air-electrode catalyst exhibited a high power density of 153 m W/cm^(2),specific capacity of 668 mAh/g and long-term cycling stability for more than 250 h.Experimental results proved that the excellent electrocatalytic ORR activity of C_(60)/FeTPP-700 would attribute to the synergistic effect between FeN_xsites,Fe_(3)C/Fe nanoparticles and the structure defects.This work provides a feasible and simple method to prepare nonnoble metal-based ORR electrocatalysts for the application of energy storage and conversion.
基金supported by the National Natural Science Foundation of China(Nos.52073166,52072226)the Xi’an Key Laboratory of Green Manufacture of Ceramic Materials Foundation(No.2019220214SYS017CG039)+5 种基金the Key Program for International S&T Cooperation Projects of Shaanxi Province(Nos.2020KW-038,2020GHJD-04)Science and Technology Program of Xi’an,China(No.2020KJRC0009)Scientific Research Program Funded by Shaanxi Provincial Education Department(No.20JY001)Science and Technology Resource Sharing Platform of Shaanxi Province(No.2020PT-022)Science and Technology Plan of Weiyang District,Xi’an(No.202009)the support from the Science and Technology Youth Stars Project of Shaanxi Province(No.2021KJXX-35)。
文摘Hydrogen evolution reaction(HER)and oxygen reduction reaction(ORR)have been considered as two critical processes in the field of electrocatalytic water-splitting for hydrogen production and fuel cells.However,the sluggish reaction kinetics of HER and ORR required efficient electrocatalyst such as Pt to promote such process.Transition metal phosphides(TMPs)exhibit great potential to replace noble metal electrocatalysts to accelerate HER and ORR due to their high activity and easy availability.Herein,a highly-efficient bifunctional CoP electrocatalyst for HER and ORR,featuring a unique core-shell structure decorated on nitrogen-doped carbon matrix was designed and constructed via etching a cobalt-based zeolitic imidazolate framework(ZIF-67)with phytic acid(PA)followed by pyrolysis treatment(PA-ZIF-67-900).Experimental results revealed that the pure-phase single-crystalline Co P exhibited outstanding electrocatalytic performance in HER and ORR,superior to Co(PO_(3))_(2) in PA-ZIF-67-700,hybrid phase of Co(PO_(3))_(2) and CoP in PA-ZIF-67-800 and Co_(2)P-doped CoP in PA-ZIF-67-1000.To reach the current density of 10 mA/cm^(2)the as-synthesized Co P required an overpotential of 120 m V for HER in 1 mol/L KOH and half-wave potential of 0.85 V in O_(2)-saturated 0.1 mol/L KOH.This work present new clue for construction of efficient and bifunctional electrocatalyst in the field of energy conversion and storage.
基金supported by the National Natural Science Foundation of China (NSFC, U1862111)China Scholarship Council (201706990062)+4 种基金Independent Research Fund Denmark-Nature Sciences (DFF-7014-00302)Independent Research Fund Denmark-Sapere Aude starting grant (7026-00037A)Swedish Research Council VR starting grant (2017-05337), grants VR2018-06011, and VR201805090the Research Fund for international Young Scientists from NSFC, China (21950410515)Swedish Energy Agency
文摘Multiple morphologies of colloidal perovskite nanocrystals(NCs)diversify their optical and electronic properties.Among them,the linear absorption cross-section(σ)is a primary parameter to determine their intrinsic photophysical features,and consequently,application potential.Herein,three morphologies of all-inorganic hybrid colloidal perovskite CsPbBr_(3)NCs,nanocubes(NBs),nanoplatelets(NLs),and nanowires(NWs),were targeted,and their linearσvalues were obtained through femtosecond transient absorption(TA)spectroscopy analysis.At high excitation energy well above the bandgap,theσper particle of all CsPbBr3 NCs linearly increased with the particle volume(VNC)regardless of the morphology with the value ofσ400=9.45×10^(4)cm^(−1)×VNC(cm^(2)).Density functional theory(DFT)calculation confirmed the negligible influence of shapes on the optical selection rules.The Einstein spontaneous emission coefficients calculated from theσvalues define the intrinsic radiative recombination rate.However,reduced size dependence is observed when the excitation energy is close to the bandgap(i.e.,at 460 nm)with the value ofσ460=2.82×10^(8)cm0.65×(VNC)0.45(cm^(2)).This should be ascribed to the discrete energy levels as well as lower density of states close to the band edge for perovskite NCs.These results provide in-depth insight into the optical characteristics for perovskite NCs.
