Incorporating a selenium(Se)positive electrode into aluminum(Al)-ion batteries is an effective strategy for improving the overall battery performance.However,the cycling stability of Se positive electrodes has challen...Incorporating a selenium(Se)positive electrode into aluminum(Al)-ion batteries is an effective strategy for improving the overall battery performance.However,the cycling stability of Se positive electrodes has challenges due to the dissolution of intermediate reaction products.In this work,we aim to harness the advantages of Se while reducing its limitations by preparing a core-shell mesoporous carbon hollow sphere with a titanium nitride(C@TiN)host to load 63.9wt%Se as the positive electrode material for Al-Se batteries.Using the physical and chemical confinement offered by the hollow mesoporous carbon and TiN,the obtained core-shell mesoporous carbon hollow spheres coated with Se(Se@C@TiN)display superior utilization of the active material and remarkable cycling stability.As a result,Al-Se batteries equipped with the as-prepared Se@C@TiN composite positive electrodes show an initial discharge specific capacity of 377 mAh·g^(-1)at a current density of 1000 mA·g^(-1)while maintaining a discharge specific capacity of 86.0 mAh·g^(-1)over 200 cycles.This improved cycling performance is ascribed to the high electrical conductivity of the core-shell mesoporous carbon hollow spheres and the unique three-dimensional hierarchical architecture of Se@C@TiN.展开更多
Rechargeable magnesium batteries(RMBs),as one of the most promising candidates for efficient energy storage devices with high energy,power density and high safety,have attracted increasing attention.However,searching ...Rechargeable magnesium batteries(RMBs),as one of the most promising candidates for efficient energy storage devices with high energy,power density and high safety,have attracted increasing attention.However,searching for suitable cathode materials with fast diffusion kinetics and exploring their magnesium storage mechanisms remains a great challenge.Cu S submicron spheres,made by a facile low-temperature synthesis strategy,were applied as the high-performance cathode for RMBs in this work,which can deliver a high specific capacity of 396mAh g^(-1)at 20 mA g^(-1) and a remarkable rate capacity of 250 m Ah g^(-1)at 1000 mA g^(-1).The excellent rate performance can be assigned to the nano needle-like particles on the surface of Cu S submicron spheres,which can facilitate the diffusion kinetics of Mg^(2+).Further storage mechanism investigations illustrate that the Cu S cathodes experience a two-step conversion reaction controlled by diffusion during the electrochemical reaction process.This work could make a contribution to the study of the enhancement of diffusion kinetics of Mg2+and the reaction mechanism of RMBs.展开更多
This paper studies two isometric problems between unit spheres of Banach spaces.In the first part,we introduce and study the Figiel type problem of isometric embeddings between unit spheres.However,the classical Figie...This paper studies two isometric problems between unit spheres of Banach spaces.In the first part,we introduce and study the Figiel type problem of isometric embeddings between unit spheres.However,the classical Figiel theorem on the whole space cannot be trivially generalized to this case,and this is pointed out by a counterexample.After establishing this,we find a natural necessary condition required by the existence of the Figiel operator.Furthermore,we prove that when X is a space with the T-property,this condition is also sufficient for an isometric embedding T:S_(X)→S_(Y) to admit the Figiel operator.This answers the Figiel type problem on unit spheres for a large class of spaces.In the second part,we consider the extension of bijectiveε-isometries between unit spheres of two Banach spaces.It is shown that every bijectiveε-isometry between unit spheres of a local GL-space and another Banach space can be extended to be a bijective 5ε-isometry between the corresponding unit balls.In particular,whenε=0,this recovers the MUP for local GL-spaces obtained in[40].展开更多
The strong metal-support interaction inducing combined effect plays a crucial role in the catalysis reaction. Herein, we revealed that the combined advantages of MoSe_(2), Ru, and hollow carbon spheres in the form of ...The strong metal-support interaction inducing combined effect plays a crucial role in the catalysis reaction. Herein, we revealed that the combined advantages of MoSe_(2), Ru, and hollow carbon spheres in the form of Ru nanoparticles(NPs) anchored on a two-dimensionally ordered MoSe_(2) nanosheet-embedded mesoporous hollow carbon spheres surface(Ru/MoSe_(2)@MHCS) for the largely boosted hydrogen evolution reaction(HER) performance. The combined advantages from the conductive support, oxyphilic MoSe_(2), and Ru active sites imparted a strong synergistic effect and charge redistribution in the Ru periphery which induced high catalytic activity, stability, and kinetics for HER. Specifically, the obtained Ru/MoSe_(2)@MHCS required a small overpotential of 25.5 and 38.4 mV to drive the kinetic current density of 10 mA cm^(-2)both in acid and alkaline media, respectively, which was comparable to that of the Pt/C catalyst. Experimental and theoretical results demonstrated that the charge transfer from MoSe_(2) to Ru NPs enriched the electronic density of Ru sites and thus facilitated hydrogen adsorption and water dissociation. The current work showed the significant interfacial engineering in Ru-based catalysts development and catalysis promotion effect understanding via the metal-support interaction.展开更多
To develop and utilize marine resources in the deep sea, the higher requirements for floating structures, which are operated in marine environment for a long term, have been put forward. Reasonable structure type and ...To develop and utilize marine resources in the deep sea, the higher requirements for floating structures, which are operated in marine environment for a long term, have been put forward. Reasonable structure type and accurate force analysis are favorable guarantees to improve the survival performance and working performance of the floating structures. Floating spheres fastened by mooring cable were widely used in floating structures. In this paper, the wave forces of the floating sphere are efficiently and accurately calculated by solving the geometric relationship between the non-submerged floating sphere and wave surface. Combined with the hydrodynamic calculation of mooring cables based on the lumped mass method, the coupled motion model of multi-floating spheres fastened by multi-mooring cable was established under wave action. Furthermore, according to the floating structures fastened by mooring cable in the actual ocean engineering, the topological method of multi-mooring cables fastening the multifloating spheres was expounded from simple to complex. Finally, the modeling method and preliminarily hydrodynamic characteristics of the fastened floating structures, including the mooring system of renewable energy devices, ocean buoy, and coral nursery, were presented and analyzed in detail. The obtained results showed that the method for calculating the wave force on the floating sphere developed in this paper can accurately describe the motion process of the floating mooring sphere and the force on the mooring cable. Also, the topological method of multiple buoys and multiple mooring cables could efficiently establish various numerical hydrodynamic models of fastened buoys in ocean engineering.展开更多
Failure of irregular rock samples may provide implications in the rapid estimation of rock strength,which is imperative in rock engineering practice.In this work,analytical,experimental and numerical investigations we...Failure of irregular rock samples may provide implications in the rapid estimation of rock strength,which is imperative in rock engineering practice.In this work,analytical,experimental and numerical investigations were carried out to study the mechanical properties and failure characteristics of rock spheres under paired point loads.Analytical solutions indicted that with the increase in sample size(contact angle)and decrease in Poisson’s ratio,the uneven tensile stress in theta direction decreased.Then laboratory experiments were carried out to investigate the load characteristics and failure mode of spherical marble samples with different sizes subjected to a pair of diametral point loads.The discrete element method(DEM)was adopted to study the failure process of rock spheres.The effect of the sphere diameter on the point load contact angle was examined in terms of peak load,crushed zone distribution and energy dissipation.Experimental and numerical results showed that the samples primarily fail in tension,with crushed zones formed at both loading points.With increase in the sample size,the contact angle,crushed area and total work increase.As the specimen diameter increases from 30 mm to 50 mm,the peak load on the specimen increases from 3.6 kN to 8.8 kN,and the percentage of crushed zone(ratio of crushing zone to sample radius,d/r)increased from 0.191 to 0.262.The results of the study have implications for understanding the failure of irregular rock specimens under point loading conditions and their size effects.展开更多
Iron is commonly used as a structural and shielding material in nuclear devices. The accuracy of its nuclear data is critical for the design of nuclear devices. The evaluation data of ^(56)Fe isotopes in the latest ve...Iron is commonly used as a structural and shielding material in nuclear devices. The accuracy of its nuclear data is critical for the design of nuclear devices. The evaluation data of ^(56)Fe isotopes in the latest version of the CENDL-3.2 library from China was significantly updated. This new data must be tested before it can be used. To test the reliability of this data and assess the shielding effect, a shielding benchmark experiment was conducted with natural Fe spherical samples using a pulsed deuterium–tritium neutron source at the China Institute of Atomic Energy(CIAE). The leakage neutron spectra from the natural spherical iron samples with different thicknesses(4.5, 7.5, and 12 cm) were measured between 0.8 and 16 MeV after interacting with 14 MeV neutrons using the time-of-flight method. The simulation results were obtained by Monte Carlo simulations by employing the Fe data from the CENDL-3.2, ENDF/B-VIII.0, and JEDNL-5.0 libraries. The measured and simulated leakage neutron spectra and penetration rates were compared, demonstrating that the CENDL-3.2 library performs sufficiently overall. The simulation results of the other two libraries were underestimated for scattering at the continuum energy level.展开更多
It is rather essential to design glorious system with high CO_(2) adsorption capacity and electron migration efficiency for improving selective and effective CO_(2) reduction into solar fuels.Here,as-synthesized pheno...It is rather essential to design glorious system with high CO_(2) adsorption capacity and electron migration efficiency for improving selective and effective CO_(2) reduction into solar fuels.Here,as-synthesized phenolic resin spheres via suspension polymerization were carbonized and activated by water vapor to obtain activated carbon spheres(ACSs).Subsequently,Bi_(2)MoO_(6)/ACSs were prepared via hydrothermal-impregnated method.The systematical characterizations of samples,including XRD,XPS,SEM,EDX,DRS,BET,PL,CO_(2) adsorption isotherm,EIS and transient photocurrent,were analyzed.The results clearly demonstrated that Bi_(2)MoO_(6) with suitable oxidation reduction potentials and bandgap and ACSs with admirable CO_(2) adsorption and electrical conductivity not only enhanced separation efficiency of photoindued electron-hole pair,but also displayed as 1.8 times CO_(2) reduction activity to CO as single Bi_(2)MoO_(6) sample under Xe-lamp irradiation.Finally,a concerned photocatalytic CO_(2) reduction mechanism was proposed and investigated.Our findings should provide innovative guidance for designing a series of photocatalytic CO_(2) reduction materials with highly efficient and selective ability.展开更多
When a shock wave interacts with a group of solid spheres,non-linear aerodynamic behaviors come into effect.The complicated wave reflections such as the Mach reflection occur in the wave propagation process.The wave i...When a shock wave interacts with a group of solid spheres,non-linear aerodynamic behaviors come into effect.The complicated wave reflections such as the Mach reflection occur in the wave propagation process.The wave interactions with vortices behind each sphere's wake cause fluctuation in the pressure profiles of shock waves.This paper reports an experimental study for the aerodynamic processes involved in the interaction between shock waves and solid spheres.A schlieren photography was applied to visualize the various shock waves passing through solid spheres.Pressure measurements were performed along different downstream positions.The experiments were conducted in both rectangular and circular shock tubes.The data with respect to the effect of the sphere array, size,interval distance,incident Mach number,etc.,on the shock wave attenuation were obtained.展开更多
This article presents the findings of a study of the spheres of urban influence with regard to all cities in China(not including Hong Kong,Macao and Taiwan Province of China)in the years 1990,2000 and 2009.An optimize...This article presents the findings of a study of the spheres of urban influence with regard to all cities in China(not including Hong Kong,Macao and Taiwan Province of China)in the years 1990,2000 and 2009.An optimized gravity model with comprehensive time distance was used to carry out a detailed analysis of the spatial patterns of Chinese spheres of urban influence and the spatial characteristics of urban agglomerations.Such urban agglomerations are characterized by high density population and a developed economy,which are also considered as the national competition unit.This paper initially identifies four spatial patterns of urban agglomerations based on the spatial layout of city groups during their evolution.Some basic characteristics of urban agglomerations are outlined,including the number of cities,the size of cities and the functions of urban centers.These characteristics are examined by using statistical methods and Geographic Information System(GIS).The main findings from this research are that the development stages and structures of urban agglomerations in China vary significantly.It is also clear that the stages and evolution of spatial patterns are strongly affected and dominated by both policy and location factors.展开更多
Currently,electromagnetic radiation and interference have a significant effect on the operation of electronic devices and human health systems.Thus,developing excellent microwave absorbers have a huge significance in ...Currently,electromagnetic radiation and interference have a significant effect on the operation of electronic devices and human health systems.Thus,developing excellent microwave absorbers have a huge significance in the material research field.Herein,a kind of ultrafine zinc oxide(ZnO)nanoparticles(NPs)supported on three-dimensional(3D)ordered mesoporous carbon spheres(ZnO/OMCS)is prepared from silica inverse opal by using phenolic resol precursor as carbon source.The prepared lightweight ZnO/OMCS nanocomposites exhibit 3D ordered carbon sphere array and highly dispersed ultrafine ZnO NPs on the mesoporous cell walls of carbon spheres.ZnO/OMCS-30 shows microwave absorbing ability with a strong absorption(−39.3 dB at 10.4 GHz with a small thickness of 2 mm)and a broad effective absorption bandwidth(9.1 GHz).The outstanding microwave absorbing ability benefits to the well-dispersed ultrafine ZnO NPs and the 3D ordered mesoporous carbon spheres structure.This work opened up a unique way for developing lightweight and high-efficient carbon-based microwave absorbing materials.展开更多
MoS_2 has attracted attention as a promising hydrogen evolution reaction(HER) catalyst and a supercapacitor electrode material. However, its catalytic activity and capacitive performance are still hindered by its aggr...MoS_2 has attracted attention as a promising hydrogen evolution reaction(HER) catalyst and a supercapacitor electrode material. However, its catalytic activity and capacitive performance are still hindered by its aggregation and poor intrinsic conductivity. Here, hollow rGO sphere-supported ultrathin MoS_2 nanosheet arrays(hrGO@MoS_2) are constructed via a dual-template approach and employed as bifunctional HER catalyst and supercapacitor electrode material. Because of the expanded interlayer spacing in MoS_2 nanosheets and more exposed electroactive S–Mo–S edges, the constructed h-rGO@MoS_2 architectures exhibit enhanced HER performance. Furthermore, benefiting from the synergistic effect of the improved conductivity and boosted specific surface areas(144.9 m^2 g^(-1), ca. 4.6-times that of pristine MoS_2), the h-rGO@MoS_2 architecture shows a high specific capacitance(238 F g^(-1) at a current density of 0.5 A g^(-1)), excellent rate capacitance, and remarkable cycle stability. Our synthesis method may be extended to construct other vertically aligned hollow architectures,which may serve both as efficient HER catalysts and supercapacitor electrodes.展开更多
Novel cost-effective fuel cells have become more attractive due to the demands for rare and expensive platinum-group metal(PGM)catalysts for mitigating the sluggish kinetics of the oxygen reduction reaction(ORR).The h...Novel cost-effective fuel cells have become more attractive due to the demands for rare and expensive platinum-group metal(PGM)catalysts for mitigating the sluggish kinetics of the oxygen reduction reaction(ORR).The high-cost PGM catalyst in fuel cells can be replaced by earth-abundant transition-metalbased catalysts,that is,an Fe-N-C catalyst,which is considered one of the most promising alternatives.However,the performance of the Fe-N-C catalyst is hindered by the low catalytic activity and poor stability,which is caused by insufficient active sites and the lack of optimization of the triple-phase interface for mass transportation.Herein,a novel Fe–N–C catalyst consisting of mono-dispersed hierarchically mesoporous carbon sphere cores and single Fe atom-dispersed functional shells are presented.The synergistic effect between highly dispersed Fe-active sites and well-organized porous structures yields the combination of high ORR activity and high mass transfer performance.The half-wave potential of the catalyst in 0.1M H_(2)SO_(4) is 0.82 V versus reversible hydrogen electrode,and the peak power density is 812 mW·cm^(−2) in H_(2)–O_(2) fuel cells.Furthermore,it shows superior methanol tolerance,which is almost immune to methanol poisoning and generates up to 162 mW·cm^(−2) power density in direct methanol fuel cells.展开更多
The triple-shelled hollow spheres with optical properties were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization.After removal the core templates of the poly(styrene),the hollow silic...The triple-shelled hollow spheres with optical properties were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization.After removal the core templates of the poly(styrene),the hollow silica spheres were obtained.The coating process of poly(methyl methacrylate)(PMMA) on the hollow silica spheres surface via surface RAFT polymerization was performed subsequently.The polymers coated on the hollow spheres surfaces were end-functionalized by trithiocarbonate,and they were used as RAFT agent to proceed the chain extension polymerization using Tb complex as monomer.The samples were characterized by FT-IR,SEM and luminescence spectroscopy respectively.The results indicated that the triple-shelled hollow spheres had been prepared successfully and the average diameter of the hollow core was about 1μm.展开更多
Abstract: We performed fluidized bed coating ofAl-based nanoeomposite powder-binder suspensions onto polymer substrates. The effects of the type and amount of the binder and nanoparticle additive on the coating proce...Abstract: We performed fluidized bed coating ofAl-based nanoeomposite powder-binder suspensions onto polymer substrates. The effects of the type and amount of the binder and nanoparticle additive on the coating process efficiency and coating characteristics were investigated. The efficiency decreased from 52% to 49% as the processing time increased from 15 to 20 min. However, the amount and thickness of the coating also increased as the processing time and amount of the binder were increased. The addition of nanoparticles to the system decreased the thickness of the coating from 222 to 207 μm when polyvinyl alcohol (PVA) was used as a binder. The suspension containing 3wt% R-4410 binder exhibited the greatest efficiency of 60%.展开更多
Ag–AgX(X = Cl, Br)@TiO_2 nanoparticle-aggregated spheres with different mass ratio of R = TiO2/Ag(X) from 35:1 to 5:1 were synthesized by a facile sol–gel technique with post-photoreduction. The photocatalytic activ...Ag–AgX(X = Cl, Br)@TiO_2 nanoparticle-aggregated spheres with different mass ratio of R = TiO2/Ag(X) from 35:1 to 5:1 were synthesized by a facile sol–gel technique with post-photoreduction. The photocatalytic activities of both Ag–Ag Cl@TiO_2 and Ag–Ag Br@TiO_2 under visible light are effectively improved by ~3 times relative to TiO_2 NPAS under the simulated sunlight for the decomposition of methyl orange(MO). Ag–AgBr@TiO_2 showed 30% improvement and less stable in photocatalytic activity than that of AgCl@TiO_2. The role of Ag and Ag X nanoparticles on the surface of Ag–Ag X(X = Cl,Br)@TiO_2 was discussed. Ag on these samples not onlycan efficiently harvest visible light especially for Ag Cl, but also efficiently separate excited electrons and holes via the fast electron transfer from Ag X(X = Cl, Br) to metal Ag nanoparticles and then to TiO_2-aggregated spheres on the surface of heterostructure. On the basis of their efficient and stable photocatalytic activities under visible-light irradiation, these photocatalysts could be widely used for degradation of organic pollutants in aqueous solution.展开更多
TiO2-coated SnO2 (TCS) hollow spheres, which are new anode materials for lithium ion (Li-ion) batteries, were prepared and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transm...TiO2-coated SnO2 (TCS) hollow spheres, which are new anode materials for lithium ion (Li-ion) batteries, were prepared and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), and galvanostatic charge/discharge tests. The results obtained from XRD, SEM, and TEM show that TiO2 can be uniforrrdy coated on the surface of SnO2 hollow spheres with the assistance of anionic surfactant. The cyclic voltammograms indicate that both TiO2 and SnO2 exhibit the activity for Li-ion storage. The charge/discharge tests show that the prepared TCS hollow spheres have a higher reversible coulomb efficiency and a better cycling stability than the uncoated SnO2 hollow spheres.展开更多
Limited lithium resources have promoted the exploration of new battery technologies.Among them,potassium-ion batteries are considered as promising alternatives.At present,commercial graphite and other carbon-based mat...Limited lithium resources have promoted the exploration of new battery technologies.Among them,potassium-ion batteries are considered as promising alternatives.At present,commercial graphite and other carbon-based materials have shown good prospects as anodes for potassium-ion batteries.However,the volume expansion and structural collapse caused by periodic K+insertion/extraction have severely restricted further development and application of potassium-ion batteries.A hollow biomass carbon ball(NOP-PB)ternarily doped with N,O,and P was synthesized and used as the negative electrode of a potassium-ion battery.X-ray photoelectron spectroscopy,Fourier‐transform infrared spectroscopy,and transmission electron microscopy confirmed that the hollow biomass carbon spheres were successfully doped with N,O,and P.Further analysis proved that N,O,and P ternary doping expands the interlayer distance of the graphite surface and introduces more defect sites.DFT calculations simultaneously proved that the K adsorption energy of the doped structure is greatly improved.The solid hollow hierarchical porous structure buffers the volume expansion of the potassium insertion process,maintains the original structure after a long cycle and promotes the transfer of potassium ions and electrons.Therefore,the NOP‐PB negative electrode shows extremely enhanced electrochemical performance,including high specific capacity,excellent long‐term stability,and good rate stability.展开更多
基金supported by the National Natural Science Foundation of China(No.52374350)China Postdoctoral Science Foundation(Nos.2020M680347 and 2021T140051)the Fundamental Research Funds for the Central Universities(No.FRF-TP-20-045A1)。
文摘Incorporating a selenium(Se)positive electrode into aluminum(Al)-ion batteries is an effective strategy for improving the overall battery performance.However,the cycling stability of Se positive electrodes has challenges due to the dissolution of intermediate reaction products.In this work,we aim to harness the advantages of Se while reducing its limitations by preparing a core-shell mesoporous carbon hollow sphere with a titanium nitride(C@TiN)host to load 63.9wt%Se as the positive electrode material for Al-Se batteries.Using the physical and chemical confinement offered by the hollow mesoporous carbon and TiN,the obtained core-shell mesoporous carbon hollow spheres coated with Se(Se@C@TiN)display superior utilization of the active material and remarkable cycling stability.As a result,Al-Se batteries equipped with the as-prepared Se@C@TiN composite positive electrodes show an initial discharge specific capacity of 377 mAh·g^(-1)at a current density of 1000 mA·g^(-1)while maintaining a discharge specific capacity of 86.0 mAh·g^(-1)over 200 cycles.This improved cycling performance is ascribed to the high electrical conductivity of the core-shell mesoporous carbon hollow spheres and the unique three-dimensional hierarchical architecture of Se@C@TiN.
基金the support from the Fundamental Research Funds for the Central Universities of Chongqing University(No.2020CDCGCL005)。
文摘Rechargeable magnesium batteries(RMBs),as one of the most promising candidates for efficient energy storage devices with high energy,power density and high safety,have attracted increasing attention.However,searching for suitable cathode materials with fast diffusion kinetics and exploring their magnesium storage mechanisms remains a great challenge.Cu S submicron spheres,made by a facile low-temperature synthesis strategy,were applied as the high-performance cathode for RMBs in this work,which can deliver a high specific capacity of 396mAh g^(-1)at 20 mA g^(-1) and a remarkable rate capacity of 250 m Ah g^(-1)at 1000 mA g^(-1).The excellent rate performance can be assigned to the nano needle-like particles on the surface of Cu S submicron spheres,which can facilitate the diffusion kinetics of Mg^(2+).Further storage mechanism investigations illustrate that the Cu S cathodes experience a two-step conversion reaction controlled by diffusion during the electrochemical reaction process.This work could make a contribution to the study of the enhancement of diffusion kinetics of Mg2+and the reaction mechanism of RMBs.
基金the National Nature Science Foundation of China(11671214,11971348,12071230)the Hundred Young Academia Leaders Program of Nankai University(63223027,ZB22000105)+1 种基金the Undergraduate Education and Teaching Project of Nankai University(NKJG2022053)the National College Students’Innovation and Entrepreneurship Training Program of Nankai University(202210055048)。
文摘This paper studies two isometric problems between unit spheres of Banach spaces.In the first part,we introduce and study the Figiel type problem of isometric embeddings between unit spheres.However,the classical Figiel theorem on the whole space cannot be trivially generalized to this case,and this is pointed out by a counterexample.After establishing this,we find a natural necessary condition required by the existence of the Figiel operator.Furthermore,we prove that when X is a space with the T-property,this condition is also sufficient for an isometric embedding T:S_(X)→S_(Y) to admit the Figiel operator.This answers the Figiel type problem on unit spheres for a large class of spaces.In the second part,we consider the extension of bijectiveε-isometries between unit spheres of two Banach spaces.It is shown that every bijectiveε-isometry between unit spheres of a local GL-space and another Banach space can be extended to be a bijective 5ε-isometry between the corresponding unit balls.In particular,whenε=0,this recovers the MUP for local GL-spaces obtained in[40].
基金supported by the National Natural Science Foundation of China (21972124, 22272148)the Priority Academic Program Development of Jiangsu Higher Education Institution。
文摘The strong metal-support interaction inducing combined effect plays a crucial role in the catalysis reaction. Herein, we revealed that the combined advantages of MoSe_(2), Ru, and hollow carbon spheres in the form of Ru nanoparticles(NPs) anchored on a two-dimensionally ordered MoSe_(2) nanosheet-embedded mesoporous hollow carbon spheres surface(Ru/MoSe_(2)@MHCS) for the largely boosted hydrogen evolution reaction(HER) performance. The combined advantages from the conductive support, oxyphilic MoSe_(2), and Ru active sites imparted a strong synergistic effect and charge redistribution in the Ru periphery which induced high catalytic activity, stability, and kinetics for HER. Specifically, the obtained Ru/MoSe_(2)@MHCS required a small overpotential of 25.5 and 38.4 mV to drive the kinetic current density of 10 mA cm^(-2)both in acid and alkaline media, respectively, which was comparable to that of the Pt/C catalyst. Experimental and theoretical results demonstrated that the charge transfer from MoSe_(2) to Ru NPs enriched the electronic density of Ru sites and thus facilitated hydrogen adsorption and water dissociation. The current work showed the significant interfacial engineering in Ru-based catalysts development and catalysis promotion effect understanding via the metal-support interaction.
基金financially supported by the National Natural Science Foundation of China (Grant No.52101330)the Basic Scientific Research Foundation of Zhejiang Provincial Universities (Grant No.2022J004)。
文摘To develop and utilize marine resources in the deep sea, the higher requirements for floating structures, which are operated in marine environment for a long term, have been put forward. Reasonable structure type and accurate force analysis are favorable guarantees to improve the survival performance and working performance of the floating structures. Floating spheres fastened by mooring cable were widely used in floating structures. In this paper, the wave forces of the floating sphere are efficiently and accurately calculated by solving the geometric relationship between the non-submerged floating sphere and wave surface. Combined with the hydrodynamic calculation of mooring cables based on the lumped mass method, the coupled motion model of multi-floating spheres fastened by multi-mooring cable was established under wave action. Furthermore, according to the floating structures fastened by mooring cable in the actual ocean engineering, the topological method of multi-mooring cables fastening the multifloating spheres was expounded from simple to complex. Finally, the modeling method and preliminarily hydrodynamic characteristics of the fastened floating structures, including the mooring system of renewable energy devices, ocean buoy, and coral nursery, were presented and analyzed in detail. The obtained results showed that the method for calculating the wave force on the floating sphere developed in this paper can accurately describe the motion process of the floating mooring sphere and the force on the mooring cable. Also, the topological method of multiple buoys and multiple mooring cables could efficiently establish various numerical hydrodynamic models of fastened buoys in ocean engineering.
文摘Failure of irregular rock samples may provide implications in the rapid estimation of rock strength,which is imperative in rock engineering practice.In this work,analytical,experimental and numerical investigations were carried out to study the mechanical properties and failure characteristics of rock spheres under paired point loads.Analytical solutions indicted that with the increase in sample size(contact angle)and decrease in Poisson’s ratio,the uneven tensile stress in theta direction decreased.Then laboratory experiments were carried out to investigate the load characteristics and failure mode of spherical marble samples with different sizes subjected to a pair of diametral point loads.The discrete element method(DEM)was adopted to study the failure process of rock spheres.The effect of the sphere diameter on the point load contact angle was examined in terms of peak load,crushed zone distribution and energy dissipation.Experimental and numerical results showed that the samples primarily fail in tension,with crushed zones formed at both loading points.With increase in the sample size,the contact angle,crushed area and total work increase.As the specimen diameter increases from 30 mm to 50 mm,the peak load on the specimen increases from 3.6 kN to 8.8 kN,and the percentage of crushed zone(ratio of crushing zone to sample radius,d/r)increased from 0.191 to 0.262.The results of the study have implications for understanding the failure of irregular rock specimens under point loading conditions and their size effects.
基金supported by the National Natural Science Foundation of China (No. 11775311)。
文摘Iron is commonly used as a structural and shielding material in nuclear devices. The accuracy of its nuclear data is critical for the design of nuclear devices. The evaluation data of ^(56)Fe isotopes in the latest version of the CENDL-3.2 library from China was significantly updated. This new data must be tested before it can be used. To test the reliability of this data and assess the shielding effect, a shielding benchmark experiment was conducted with natural Fe spherical samples using a pulsed deuterium–tritium neutron source at the China Institute of Atomic Energy(CIAE). The leakage neutron spectra from the natural spherical iron samples with different thicknesses(4.5, 7.5, and 12 cm) were measured between 0.8 and 16 MeV after interacting with 14 MeV neutrons using the time-of-flight method. The simulation results were obtained by Monte Carlo simulations by employing the Fe data from the CENDL-3.2, ENDF/B-VIII.0, and JEDNL-5.0 libraries. The measured and simulated leakage neutron spectra and penetration rates were compared, demonstrating that the CENDL-3.2 library performs sufficiently overall. The simulation results of the other two libraries were underestimated for scattering at the continuum energy level.
基金The authors are thankful to the National Natural Science Foundation of China(No.21978196,21676178,21706179)Shanxi Province Science Foundation for Youths(201801D211008).
文摘It is rather essential to design glorious system with high CO_(2) adsorption capacity and electron migration efficiency for improving selective and effective CO_(2) reduction into solar fuels.Here,as-synthesized phenolic resin spheres via suspension polymerization were carbonized and activated by water vapor to obtain activated carbon spheres(ACSs).Subsequently,Bi_(2)MoO_(6)/ACSs were prepared via hydrothermal-impregnated method.The systematical characterizations of samples,including XRD,XPS,SEM,EDX,DRS,BET,PL,CO_(2) adsorption isotherm,EIS and transient photocurrent,were analyzed.The results clearly demonstrated that Bi_(2)MoO_(6) with suitable oxidation reduction potentials and bandgap and ACSs with admirable CO_(2) adsorption and electrical conductivity not only enhanced separation efficiency of photoindued electron-hole pair,but also displayed as 1.8 times CO_(2) reduction activity to CO as single Bi_(2)MoO_(6) sample under Xe-lamp irradiation.Finally,a concerned photocatalytic CO_(2) reduction mechanism was proposed and investigated.Our findings should provide innovative guidance for designing a series of photocatalytic CO_(2) reduction materials with highly efficient and selective ability.
基金The project supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry,China,and the "BaiRen" Plan of Chinese Academy of Sciences
文摘When a shock wave interacts with a group of solid spheres,non-linear aerodynamic behaviors come into effect.The complicated wave reflections such as the Mach reflection occur in the wave propagation process.The wave interactions with vortices behind each sphere's wake cause fluctuation in the pressure profiles of shock waves.This paper reports an experimental study for the aerodynamic processes involved in the interaction between shock waves and solid spheres.A schlieren photography was applied to visualize the various shock waves passing through solid spheres.Pressure measurements were performed along different downstream positions.The experiments were conducted in both rectangular and circular shock tubes.The data with respect to the effect of the sphere array, size,interval distance,incident Mach number,etc.,on the shock wave attenuation were obtained.
基金Under the auspices of National Natural Science Foundation of China(No.40901088,41271174)
文摘This article presents the findings of a study of the spheres of urban influence with regard to all cities in China(not including Hong Kong,Macao and Taiwan Province of China)in the years 1990,2000 and 2009.An optimized gravity model with comprehensive time distance was used to carry out a detailed analysis of the spatial patterns of Chinese spheres of urban influence and the spatial characteristics of urban agglomerations.Such urban agglomerations are characterized by high density population and a developed economy,which are also considered as the national competition unit.This paper initially identifies four spatial patterns of urban agglomerations based on the spatial layout of city groups during their evolution.Some basic characteristics of urban agglomerations are outlined,including the number of cities,the size of cities and the functions of urban centers.These characteristics are examined by using statistical methods and Geographic Information System(GIS).The main findings from this research are that the development stages and structures of urban agglomerations in China vary significantly.It is also clear that the stages and evolution of spatial patterns are strongly affected and dominated by both policy and location factors.
基金The authors are grateful of the financial support by the National Natural Science Foundation of China(51902083 and 21606068)the Foundation Strengthening Program(2019-JCJQ-142-00)the Higher Education Science and Technology Research Project of Hebei Province(ZD2019087).
文摘Currently,electromagnetic radiation and interference have a significant effect on the operation of electronic devices and human health systems.Thus,developing excellent microwave absorbers have a huge significance in the material research field.Herein,a kind of ultrafine zinc oxide(ZnO)nanoparticles(NPs)supported on three-dimensional(3D)ordered mesoporous carbon spheres(ZnO/OMCS)is prepared from silica inverse opal by using phenolic resol precursor as carbon source.The prepared lightweight ZnO/OMCS nanocomposites exhibit 3D ordered carbon sphere array and highly dispersed ultrafine ZnO NPs on the mesoporous cell walls of carbon spheres.ZnO/OMCS-30 shows microwave absorbing ability with a strong absorption(−39.3 dB at 10.4 GHz with a small thickness of 2 mm)and a broad effective absorption bandwidth(9.1 GHz).The outstanding microwave absorbing ability benefits to the well-dispersed ultrafine ZnO NPs and the 3D ordered mesoporous carbon spheres structure.This work opened up a unique way for developing lightweight and high-efficient carbon-based microwave absorbing materials.
基金financially supported by the Natural Science Foundation of China (Grant No.21473093)Fundamental Research Funds for the Central Universities and Tianjin Research Program of Application Foundation and Advanced Technology (Grant No.14JCYBJC41300)Ph.D. Candidate Research Innovation Fund of Nankai University
文摘MoS_2 has attracted attention as a promising hydrogen evolution reaction(HER) catalyst and a supercapacitor electrode material. However, its catalytic activity and capacitive performance are still hindered by its aggregation and poor intrinsic conductivity. Here, hollow rGO sphere-supported ultrathin MoS_2 nanosheet arrays(hrGO@MoS_2) are constructed via a dual-template approach and employed as bifunctional HER catalyst and supercapacitor electrode material. Because of the expanded interlayer spacing in MoS_2 nanosheets and more exposed electroactive S–Mo–S edges, the constructed h-rGO@MoS_2 architectures exhibit enhanced HER performance. Furthermore, benefiting from the synergistic effect of the improved conductivity and boosted specific surface areas(144.9 m^2 g^(-1), ca. 4.6-times that of pristine MoS_2), the h-rGO@MoS_2 architecture shows a high specific capacitance(238 F g^(-1) at a current density of 0.5 A g^(-1)), excellent rate capacitance, and remarkable cycle stability. Our synthesis method may be extended to construct other vertically aligned hollow architectures,which may serve both as efficient HER catalysts and supercapacitor electrodes.
基金We gratefully acknowledge support from the National Natural Science Foundation of China(Grant Nos.21905220,51772240,21503158,51425301,U1601214,21703184)the China Postdoctoral Science Foundation(2020M673408)+5 种基金the Key Research and Development Plan of Shaanxi Province,China(Grant No.2018ZDXM-GY-135)the Fundamental Research Funds for“Young Talent Support Plan”of Xi'an Jiaotong University(HG6J003)the“1000‐Plan program”of Shaanxi Province,the Promotion Program for Young and Middle-Aged Teacher in Science and Technology Research of Huaqiao University(ZQN-PY506)the Scientific Research Funds of Huaqiao University(17BS405)the State Key Laboratory for Mechanical Behavior of Materials(20192101)the Natural Science Foundation Committee of Jiangsu Province(BK20201190).
文摘Novel cost-effective fuel cells have become more attractive due to the demands for rare and expensive platinum-group metal(PGM)catalysts for mitigating the sluggish kinetics of the oxygen reduction reaction(ORR).The high-cost PGM catalyst in fuel cells can be replaced by earth-abundant transition-metalbased catalysts,that is,an Fe-N-C catalyst,which is considered one of the most promising alternatives.However,the performance of the Fe-N-C catalyst is hindered by the low catalytic activity and poor stability,which is caused by insufficient active sites and the lack of optimization of the triple-phase interface for mass transportation.Herein,a novel Fe–N–C catalyst consisting of mono-dispersed hierarchically mesoporous carbon sphere cores and single Fe atom-dispersed functional shells are presented.The synergistic effect between highly dispersed Fe-active sites and well-organized porous structures yields the combination of high ORR activity and high mass transfer performance.The half-wave potential of the catalyst in 0.1M H_(2)SO_(4) is 0.82 V versus reversible hydrogen electrode,and the peak power density is 812 mW·cm^(−2) in H_(2)–O_(2) fuel cells.Furthermore,it shows superior methanol tolerance,which is almost immune to methanol poisoning and generates up to 162 mW·cm^(−2) power density in direct methanol fuel cells.
基金a project of Shandong Province Higher Education Science and Technology Program(No.J09LD56)the Scientific Research Start up Fund for Doctor of Liaocheng University.
文摘The triple-shelled hollow spheres with optical properties were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization.After removal the core templates of the poly(styrene),the hollow silica spheres were obtained.The coating process of poly(methyl methacrylate)(PMMA) on the hollow silica spheres surface via surface RAFT polymerization was performed subsequently.The polymers coated on the hollow spheres surfaces were end-functionalized by trithiocarbonate,and they were used as RAFT agent to proceed the chain extension polymerization using Tb complex as monomer.The samples were characterized by FT-IR,SEM and luminescence spectroscopy respectively.The results indicated that the triple-shelled hollow spheres had been prepared successfully and the average diameter of the hollow core was about 1μm.
文摘Abstract: We performed fluidized bed coating ofAl-based nanoeomposite powder-binder suspensions onto polymer substrates. The effects of the type and amount of the binder and nanoparticle additive on the coating process efficiency and coating characteristics were investigated. The efficiency decreased from 52% to 49% as the processing time increased from 15 to 20 min. However, the amount and thickness of the coating also increased as the processing time and amount of the binder were increased. The addition of nanoparticles to the system decreased the thickness of the coating from 222 to 207 μm when polyvinyl alcohol (PVA) was used as a binder. The suspension containing 3wt% R-4410 binder exhibited the greatest efficiency of 60%.
基金supported by the China Postdoctoral Science Foundation (2016M602647)the Science and Technology Research Project of Chongqing Municipal Education Commission of China (KJ1400607)+3 种基金the Fundamental Research Funds for the Central Universities (CQDXWL-2014-001)NSFCQ (cstc2015jcyj A20020)NSFC (51572040, 51402112)National High Technology Research and Development Program of China (2015AA034801)
文摘Ag–AgX(X = Cl, Br)@TiO_2 nanoparticle-aggregated spheres with different mass ratio of R = TiO2/Ag(X) from 35:1 to 5:1 were synthesized by a facile sol–gel technique with post-photoreduction. The photocatalytic activities of both Ag–Ag Cl@TiO_2 and Ag–Ag Br@TiO_2 under visible light are effectively improved by ~3 times relative to TiO_2 NPAS under the simulated sunlight for the decomposition of methyl orange(MO). Ag–AgBr@TiO_2 showed 30% improvement and less stable in photocatalytic activity than that of AgCl@TiO_2. The role of Ag and Ag X nanoparticles on the surface of Ag–Ag X(X = Cl,Br)@TiO_2 was discussed. Ag on these samples not onlycan efficiently harvest visible light especially for Ag Cl, but also efficiently separate excited electrons and holes via the fast electron transfer from Ag X(X = Cl, Br) to metal Ag nanoparticles and then to TiO_2-aggregated spheres on the surface of heterostructure. On the basis of their efficient and stable photocatalytic activities under visible-light irradiation, these photocatalysts could be widely used for degradation of organic pollutants in aqueous solution.
基金financially supported by the National Natural Science Foundation of China (No.20873046)the Specialized Research Fund for the Doctoral Program of HigherEducation (No.200805740004)Natural Science Foundation of Guangdong Province (No.10351063101000001)
文摘TiO2-coated SnO2 (TCS) hollow spheres, which are new anode materials for lithium ion (Li-ion) batteries, were prepared and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), and galvanostatic charge/discharge tests. The results obtained from XRD, SEM, and TEM show that TiO2 can be uniforrrdy coated on the surface of SnO2 hollow spheres with the assistance of anionic surfactant. The cyclic voltammograms indicate that both TiO2 and SnO2 exhibit the activity for Li-ion storage. The charge/discharge tests show that the prepared TCS hollow spheres have a higher reversible coulomb efficiency and a better cycling stability than the uncoated SnO2 hollow spheres.
基金The authors are grateful for support from the National Natural Science Foundation of China(No.21671160).
文摘Limited lithium resources have promoted the exploration of new battery technologies.Among them,potassium-ion batteries are considered as promising alternatives.At present,commercial graphite and other carbon-based materials have shown good prospects as anodes for potassium-ion batteries.However,the volume expansion and structural collapse caused by periodic K+insertion/extraction have severely restricted further development and application of potassium-ion batteries.A hollow biomass carbon ball(NOP-PB)ternarily doped with N,O,and P was synthesized and used as the negative electrode of a potassium-ion battery.X-ray photoelectron spectroscopy,Fourier‐transform infrared spectroscopy,and transmission electron microscopy confirmed that the hollow biomass carbon spheres were successfully doped with N,O,and P.Further analysis proved that N,O,and P ternary doping expands the interlayer distance of the graphite surface and introduces more defect sites.DFT calculations simultaneously proved that the K adsorption energy of the doped structure is greatly improved.The solid hollow hierarchical porous structure buffers the volume expansion of the potassium insertion process,maintains the original structure after a long cycle and promotes the transfer of potassium ions and electrons.Therefore,the NOP‐PB negative electrode shows extremely enhanced electrochemical performance,including high specific capacity,excellent long‐term stability,and good rate stability.