Selective coupling of methyl radicals to produce C_(2) species(C2H4 and C2H6)is a key challenge for oxidative coupling of methane(OCM).In traditional OCM reaction systems,homogeneous transformation of methyl radicals ...Selective coupling of methyl radicals to produce C_(2) species(C2H4 and C2H6)is a key challenge for oxidative coupling of methane(OCM).In traditional OCM reaction systems,homogeneous transformation of methyl radicals in O_(2)‐containing gases are uncontrollable,resulting in limited C_(2) selectivity and yield.Herein,we demonstrate that methyl radicals generated by La_(2)O_(3)at low reaction temperature can selectively couple on the surface of 5 wt%Na2WO4/SiO_(2).The controllable surface coupling against overoxidation barely changes the activity of La_(2)O_(3)but boosts the C_(2)selectivity by three times and achieves a C_(2)yield as high as 10.9%at bed temperature of only 570℃.Structure‐property studies suggest that Na_(2)WO_(4) nanoclusters are the active sites for methyl radical coupling.The strong CH_(3)·affinity of these sites can even endow some methane combustion catalysts with OCM activity.The findings of the surface coupling of methyl radicals open a new direction to develop OCM catalyst.The bifunctional OCM catalyst system,which composes of a methane activation center and a CH_(3)·coupling center,may deliver promising OCM performance at reaction temperatures below the ignition temperature of C2H6 and C2H4(~600℃)and is therefore more controllable,safer,and certainly more attractive as an actual process.展开更多
The restriction of the molecular motion has been extensively exploited in tailoring the photoluminescence(PL)of metal nanoclusters,while the activation of such a restriction at the molecular level remains highly chall...The restriction of the molecular motion has been extensively exploited in tailoring the photoluminescence(PL)of metal nanoclusters,while the activation of such a restriction at the molecular level remains highly challenging.In this work,a two-step strategy,that is,surface activating and surface coupling,was proposed to induce the restriction of the molecular motion of nanoclusters at the molecular level,and the corresponding nanoclusters underwent emission appearance and enhancement.The peripheral phosphine ligand functionalization and alkali metal cation introduction gave rise to a series of structural-correlated M^(+)-incorporated Cu14 nanoclusters(M=Li,Na,K,Rb,Cs)with a surface-aggregation characteristic,among which the K^(+)-participating nanocluster displayed the strongest fluorescence intensity in both solution and crystal states.Atomic-level structure–property correlations were investigated to rationalize the PL comparisons.Overall,this work offers a new perspective for regulating the PL of metal nanoclusters via restricting their molecular motions,hopefully providing insight into the fabrication of highly emissive metal nanoclusters and cluster-based nanomaterials.展开更多
In Earth system modeling,the land surface is coupled with the atmosphere through surface turbulent fluxes.These fluxes are computed using mean meteorological variables between the surface and a reference height in the...In Earth system modeling,the land surface is coupled with the atmosphere through surface turbulent fluxes.These fluxes are computed using mean meteorological variables between the surface and a reference height in the atmosphere.However,the dependence of flux computation on the reference height,which is usually set as the lowest level in the atmosphere in Earth system models,has not received much attention.Based on high-resolution large-eddy simulation(LES)data under unstable conditions,we find the setting of reference height is not trivial within the framework of current surface layer theory.With a reasonable prescription of aerodynamic roughness length(following the setting in LESs),reference heights near the top of the surface layer tend to provide the best estimate of surface fluxes,especially for the momentum flux.Furthermore,this conclusion for the sensible heat flux is insensitive to the ratio of roughness length for momentum versus heat.These results are robust,whether using the classical or revised surface layer theory.They provide a potential guide for setting the proper reference heights for Earth system modeling and can be further tested in the near future using observational data from land–atmosphere feedback observatories.展开更多
The production of C_(2)H_(3)Cl from CH_(3)Cl(MCTV)represents a promising non-petroleum route for synthesizing C_(2)alkenes from C_(1)molecules.Exploration of new MCTV catalysts is crucial for advancing sustainable che...The production of C_(2)H_(3)Cl from CH_(3)Cl(MCTV)represents a promising non-petroleum route for synthesizing C_(2)alkenes from C_(1)molecules.Exploration of new MCTV catalysts is crucial for advancing sustainable chemical production.In this study,we present NaVO_(3)as a surface-confined coupling center for·CH_(2)Cl radicals,demonstrating its superior performance in the selective coupling of methyl chloride to synthesize vinyl chloride.By incorporating NaVO_(3)onto the surface of CeO_(2),the catalyst enables effective capture of·CH_(2)Cl radicals during the CH_(3)Cl oxidative pyrolysis and their subsequent conversion into C_(2)H_(3)Cl.We experimentally validate the capability of highly dispersed Na-VO_(3)to controllably couple·CH_(2)Cl radicals through in-situ synchrotron-based vacuum ultraviolet photoionization mass spectrometry.The results demonstrate that the dispersion of NaVO_(3)on the catalyst surface has a considerable impact on the reaction efficiency of·CH_(2)Cl radicals and the overall MCTV performance.This discovery holds substantial implications for the controlled C_(1)radical transformation and provides a guidance for the design of catalysts for sustainable production of C_(2)H_(3)Cl.展开更多
We report a non-destructive characterization of planar two-dimensional （2D） photonic crystals （PhCs） made in silicon on insulator （SOI） wafers using ellipsometric or Fourier transformed infrared （FTIR） spectro...We report a non-destructive characterization of planar two-dimensional （2D） photonic crystals （PhCs） made in silicon on insulator （SOI） wafers using ellipsometric or Fourier transformed infrared （FTIR） spectroscope. At large wavelengths, devices behave as homogeneous isotropic materials defined by an effective filling factor. The experimental results related to the PhC limited dimensions confirm this characterization.展开更多
We use the method of discrete dipole approximation with surface interaction to construct a model in which a plurality of nanoparticles is arranged on the surface of BK7 glass. Nanoparticles are in air medium illuminat...We use the method of discrete dipole approximation with surface interaction to construct a model in which a plurality of nanoparticles is arranged on the surface of BK7 glass. Nanoparticles are in air medium illuminated by evanescent wave generated from total internal reflection. The effects of the wavelength, the polarization of the incident wave, the number of nanoparticles and the spacing of multiple nanoparticles on the field enhancement and extinction efficiency are calculated by our model. Our work could pave the way to improve the field enhancement of multiple nanoparticles systems.展开更多
Photoluminescence(PL)was investigated as functions of the excitation intensity and temperature for a coupling surface quantum dots(SQDs)structure which consists of one In_(0.3)Ga_(0.7)As SQDs layer being stacked on mu...Photoluminescence(PL)was investigated as functions of the excitation intensity and temperature for a coupling surface quantum dots(SQDs)structure which consists of one In_(0.3)Ga_(0.7)As SQDs layer being stacked on multi-layers of In_(0.3)Ga_(0.7)As buried quantum dots(BQDs).Accompanied by considering the localized excitons effect induced by interface fluctuation,carrier transition between BQDs and SQDs were analyzed carefully.The PL measurements confirm that there is a strong carrier transition from BQDs to SQDs and this transition leads to obvious different PL characteristics between BQDs and SQDs.These results are useful for future application of SQDs as surface sensitive sensors.展开更多
High performance electromechanical equipment is widely used in various fields, such as national defense, industry and so on [ 1]. In addition, the technical level of high performance electromechanical equipment is the...High performance electromechanical equipment is widely used in various fields, such as national defense, industry and so on [ 1]. In addition, the technical level of high performance electromechanical equipment is the embodiment of the national level of science and technology.展开更多
The main methods of the existing multi-spiral surface geometry modeling include spatial analytic geometry algorithms, graphical method, interpolation and approximation algorithms. However, there are some shortcomings ...The main methods of the existing multi-spiral surface geometry modeling include spatial analytic geometry algorithms, graphical method, interpolation and approximation algorithms. However, there are some shortcomings in these modeling methods, such as large amount of calculation, complex process, visible errors, and so on. The above methods have, to some extent, restricted the design and manufacture of the premium and high-precision products with spiral surface considerably. This paper introduces the concepts of the spatially parallel coupling with multi-spiral surface and spatially parallel coupling body. The typical geometry and topological features of each spiral surface forming the multi-spiral surface body are determined, by using the extraction principle of datum point cluster, the algorithm of coupling point cluster by removing singular point, and the ＂spatially parallel coupling＂ principle based on the non-uniform B-spline for each spiral surface. The orientation and quantitative relationships of datum point cluster and coupling point cluster in Euclidean space are determined accurately and in digital description and expression, coupling coalescence of the surfaces with multi-coupling point clusters under the Pro/E environment. The digitally accurate modeling of spatially parallel coupling body with multi-spiral surface is realized. The smooth and fairing processing is done to the three-blade end-milling cutter＇s end section area by applying the principle of spatially parallel coupling with multi-spiral surface, and the alternative entity model is processed in the four axis machining center after the end mill is disposed. And the algorithm is verified and then applied effectively to the transition area among the multi-spiral surface. The proposed model and algorithms may be used in design and manufacture of the multi-spiral surface body products, as well as in solving essentially the problems of considerable modeling errors in computer graphics and engineering in multi-spiral surface＇s connection available with approximate methods or graphical methods.展开更多
This study investigated the seasonal variation in the atmospheric response to oceanic mesoscale eddies in the North Pacific Subtropical Countercurrent(STCC)and its mechanism,based on satellite altimetric and reanalysi...This study investigated the seasonal variation in the atmospheric response to oceanic mesoscale eddies in the North Pacific Subtropical Countercurrent(STCC)and its mechanism,based on satellite altimetric and reanalysis datasets.Although mesoscale eddy in the study area is more active in summer,the sea surface temperature(SST)anomaly associated with mesoscale eddies is more intense and dipolar in winter,which is largely due to the larger background SST gradient.Similarly,the impact of the oceanic eddy on sea surface wind speed and heat flux is strongest in winter,whereas its effect on precipitation rate is more significant in summer.The study revealed that the SST gradient in STCC could impact the atmosphere layer by up to 800 h Pa(900 h Pa)in boreal winter(summer)through the dominant vertical mixing mechanism.Moreover,the intensity of the SST gradient causes such seasonal variation in mesoscale air-sea coupling in the study region.In brief,a stronger(weaker)background SST gradient field in wintertime(summertime)leads to a larger(smaller)eddy-induced SST anomaly,thus differently impacting atmosphere instability and transitional kinetic energy flux over oceanic eddies,leading to seasonal variation in mesoscale air-sea coupling intensity.展开更多
Simultaneous acquisition of fluorescence property and refractive index using a single surface plasmon coupled emission(SPCE)measurement has been achieved,thus achieving synchronicity in real time.The SPCE sensor was e...Simultaneous acquisition of fluorescence property and refractive index using a single surface plasmon coupled emission(SPCE)measurement has been achieved,thus achieving synchronicity in real time.The SPCE sensor was employed for monitoring the adsorption of volatile organic compounds(VOCs)by dyeencapsulated metal-organic frameworks(Dye@MOFs).Refractive index can reveal surface molecular adsorption and the fluorescence with information on refractive index can provide a comprehensive analysis of the adsorption events of VOCs on the interface.Meantime,the signal intensity can be amplified by combining the responses caused by changes in refractive index and the fluorescence property in parallel.This all-in-one method opens up a route to monitoring multiple processes simultaneously occurring on the interface.展开更多
The obvious enhancement effect of magnetic nanoparticles(MNPs) introduced in Cr/Co/Cr/Au substrate on the pulsed magnetic field-modulated surface plasmon coupled emission(SPCE) was investigated,and the observed enhanc...The obvious enhancement effect of magnetic nanoparticles(MNPs) introduced in Cr/Co/Cr/Au substrate on the pulsed magnetic field-modulated surface plasmon coupled emission(SPCE) was investigated,and the observed enhancement factor was 4 comparing with the magnetic field modulated SPCE without MNPs.This is the new observation for the magnetic field modulated SPCE,and this method was designed as a biosensor,which to our knowledge,is the first application of magnetic field-modulated SPCE in biosensing and detection field.This strategy is a universal approach to increase the fluorescence signal and helps to build the new SPCE based stimulus-response system.展开更多
Water stored as part of the land surface is lost to evapotranspiration and runoff on different time scales, and the partitioning between these time scales is important for modeling soil water in a climate model. Diffe...Water stored as part of the land surface is lost to evapotranspiration and runoff on different time scales, and the partitioning between these time scales is important for modeling soil water in a climate model. Different time scales are imposed on evapotranspiration primarily because it is derived from different reservoirs with different storage capacities, from the very rapid evaporation of canopy stores to the slow removal by transpiration of rooting zone soil moisture. Runoff likewise ranges in time scale from rapid surface terms to the slower base-flow. The longest time scale losses of water determine the slow variation of soil moisture and hence the longer time scale effects of soil moisture on precipitation. This paper shows with a simple analysis how shifting the partitioning of evapotranspiration between the different reservoirs affects the variability of soil moisture and precipitation. In particular, it is concluded that a shift to shorter time scale reservoirs shifts the variance of precipitation from that which is potentially predictable to unpredictable.展开更多
This article describes the development and application of a streamlined air control and response modeling system with a novel response surface modeling-linear coupled fitting method and a new module to provide streaml...This article describes the development and application of a streamlined air control and response modeling system with a novel response surface modeling-linear coupled fitting method and a new module to provide streamlined model data for PM_（2.5） attainment assessment in China.This method is capable of significantly reducing the dimensions required to establish a response surface model,as well as capturing more realistic response of PM_（2.5） to emission changes with a limited number of model simulations.The newly developed module establishes a data link between the system and the Software for Model Attainment Test—Community Edition（SMAT-CE）,and has the ability to rapidly provide model responses to emission control scenarios for SMAT-CE using a simple interface.The performance of this streamlined system is demonstrated through a case study of the Yangtze River Delta（YRD） in China.Our results show that this system is capable of reproducing the Community Multi-Scale Air Quality（CMAQ） model simulation results with maximum mean normalized error 〈 3.5%.It is also demonstrated that primary emissions make a major contribution to ambient levels of PM_（2.5） in January and August（e.g.,more than50%contributed by primary emissions in Shanghai）,and Shanghai needs to have regional emission control both locally and in its neighboring provinces to meet China＇s annual PM_（2.5）National Ambient Air Quality Standard.The streamlined system provides a real-time control/response assessment to identify the contributions of major emission sources to ambient PM_（2.5）（and potentially O_3 as well） and streamline air quality data for SMAT-CE to perform attainment assessments.展开更多
Based on the finite difference time domain method, we investigated theoretically the optical properties and the plasmonic interactions between a gold film perforated with periodic sub-wavelength holes and a thin gold ...Based on the finite difference time domain method, we investigated theoretically the optical properties and the plasmonic interactions between a gold film perforated with periodic sub-wavelength holes and a thin gold film. We showed that the plasmon resonant energies and intensities depend strongly on the thicknesses of the two films and the lattice constant. Based on the distributions of normal electric field component Ez, tangential electric field component Ey and total energy, we showed that the optical transmission is due to the collaboration of the localized waveguide resonance, the surface plasmon resonance and the coupling of the fiat-surface plasmon of the two layers.展开更多
We propose a design for efficient end-fire coupling of surface plasmon polaritons in a metal-insulator-metal(MIM) waveguide with an optical fiber as part of a simple photoplastic connector. The design was analyzed and...We propose a design for efficient end-fire coupling of surface plasmon polaritons in a metal-insulator-metal(MIM) waveguide with an optical fiber as part of a simple photoplastic connector. The design was analyzed and optimized using the three-dimensional finite-difference time-domain method. The calculated excitation efficiency coefficient of the waveguide is 83.7%(-0.77 dB) at a wavelength of 405 nm. This design enables simple connection of an optical fiber to a MIM waveguide and highly efficient local excitation of the waveguide.Moreover, the length of the metallic elements of the waveguide, and thus the dissipative losses, can be reduced.The proposed design may be useful in plasmonic-type waveguide applications such as near-field investigation of live cells and other objects with super-resolution.展开更多
Based on observations and Coupled Model lntercomparison Project Phase 5 （CMIP5） results, multidecadal variations and trends in annual mean surface air temperature anomalies （SATa） at global, hemispheric, and hemis...Based on observations and Coupled Model lntercomparison Project Phase 5 （CMIP5） results, multidecadal variations and trends in annual mean surface air temperature anomalies （SATa） at global, hemispheric, and hemispheric land and ocean scales in the past and under the future scenarios of two representative concentration pathways （RCPs） are analyzed. Fifteen models are selected based on their performances in capturing the temporal variability, long-term trend, multidecadal variations, and trends in global annual mean SATa. Observational data analysis shows that the multidecadal variations in annual mean SATa of the land and ocean in the northern hemisphere （NH） and of the ocean in the southern hemisphere （SH） are similar to those of the global mean, showing an increase during the 1900-1944 and 1971-2000 periods, and flattening or even cooling during the 1945-1970 and 2001-2013 periods. These observed characteristics are basically reproduced by the models. However, SATa over SH land show an increase during the 1945-1970 period, which differs from the other hemispheric scales, and this feature is not captured well by the models. For the recent hiatus period （2001-2013）, the projected trends of BCC-CSM1-1-m, CMCC-CM, GFDL-ESM2M, and NorESM1-ME at the global and hemispheric scales are closest to the observations based on RCP4.5 and RCP8.5 scenarios, suggesting that these four models have better projection capability in SATa. Because these four models are better at simulating and projecting the multidecadal trends of SATa, they are selected to analyze future SATa variations at the global and hemispheric scales during the 2006-2099 period. The selected multi-model ensemble （MME） projected trends in annual mean SATa for the globe, NH, and SH under RCP4.5 （RCP8.5） are 0.17 （0.29） ℃, 0.22 （0.36） ℃, and 0.11 （0.23） ℃-decade-1 in the 21st century, respectively. These values are significantly lower than the projections of CMIP5 MME without model selection.展开更多
Cavity optomechanics is applied to study the coupling behavior of interacting molecules in surface plasmon systems driven by two-color laser beams. Different from the traditional force–distance measurement, due to a ...Cavity optomechanics is applied to study the coupling behavior of interacting molecules in surface plasmon systems driven by two-color laser beams. Different from the traditional force–distance measurement, due to a resonant frequency shift or a peak splitting on the probe spectrum, we have proposed a convenient method to measure the van der Waals force strength and interaction energy via nonlinear spectroscopy. The minimum force value can reach approximately 10^(-15) N, which is 3 to 4 orders of magnitude smaller than the widely applied atomic force microscope(AFM). It is also shown that two adjacent molecules with similar chemical structures and nearly equal vibrational frequencies can be easily distinguished by the splitting of the transparency peak. Based on this coupled optomechanical system, we also conceptually design a tunable optical switch by van der Waals interaction. Our results will provide new approaches for understanding the complex and dynamic interactions inmolecule–plasmon systems.展开更多
The ionic and neutral state potential energy surfaces (PESs) of Na+I 2 collision system have been calculated on QCISD(T) level by using ab initio method. The location and depth of the potential well, the collisio...The ionic and neutral state potential energy surfaces (PESs) of Na+I 2 collision system have been calculated on QCISD(T) level by using ab initio method. The location and depth of the potential well, the collision radius and their fine structures have been analyzed at the equilibrium geometry of I 2 molecule. The electronic transfer probabilities are also calculated in terms of Landau Zener model. The lifetime of scattering resonance state is evaluated by the uncertainty principle. All the results have been compared with those obtained according to the Aten Lanting Los PES and Feng's PES.展开更多
In this paper, we have analyzed the processes of temporal and spatial development in the interaction be- tween the Northern Oscillation and the sea surface temperature of the cquatorial Pacific. It is revealed that be...In this paper, we have analyzed the processes of temporal and spatial development in the interaction be- tween the Northern Oscillation and the sea surface temperature of the cquatorial Pacific. It is revealed that between them there is a closed negative feedback process and the whole period including their influence, feedback and adjustment to each other is about 3.5 years. Furthermore, we have discussed the physical processes responsible for various links between the Northern Oscillation and the sea surface temperature of the equatorial Pacific. A physical model on 3.5-year coupled oscillation caused by the air-sea interaction in the tropical Pacific is postulated.展开更多
文摘Selective coupling of methyl radicals to produce C_(2) species(C2H4 and C2H6)is a key challenge for oxidative coupling of methane(OCM).In traditional OCM reaction systems,homogeneous transformation of methyl radicals in O_(2)‐containing gases are uncontrollable,resulting in limited C_(2) selectivity and yield.Herein,we demonstrate that methyl radicals generated by La_(2)O_(3)at low reaction temperature can selectively couple on the surface of 5 wt%Na2WO4/SiO_(2).The controllable surface coupling against overoxidation barely changes the activity of La_(2)O_(3)but boosts the C_(2)selectivity by three times and achieves a C_(2)yield as high as 10.9%at bed temperature of only 570℃.Structure‐property studies suggest that Na_(2)WO_(4) nanoclusters are the active sites for methyl radical coupling.The strong CH_(3)·affinity of these sites can even endow some methane combustion catalysts with OCM activity.The findings of the surface coupling of methyl radicals open a new direction to develop OCM catalyst.The bifunctional OCM catalyst system,which composes of a methane activation center and a CH_(3)·coupling center,may deliver promising OCM performance at reaction temperatures below the ignition temperature of C2H6 and C2H4(~600℃)and is therefore more controllable,safer,and certainly more attractive as an actual process.
基金funded by NSFC(22371003,22101001,22471001,and 22273095)The Ministry of Education,Natural Science Foundation of Anhui Province(2408085Y006)+1 种基金The University Synergy Innovation Program of Anhui Province(GXXT-2020-053)The Scientific Research Program of Universities in Anhui Province(2022AH030009).
文摘The restriction of the molecular motion has been extensively exploited in tailoring the photoluminescence(PL)of metal nanoclusters,while the activation of such a restriction at the molecular level remains highly challenging.In this work,a two-step strategy,that is,surface activating and surface coupling,was proposed to induce the restriction of the molecular motion of nanoclusters at the molecular level,and the corresponding nanoclusters underwent emission appearance and enhancement.The peripheral phosphine ligand functionalization and alkali metal cation introduction gave rise to a series of structural-correlated M^(+)-incorporated Cu14 nanoclusters(M=Li,Na,K,Rb,Cs)with a surface-aggregation characteristic,among which the K^(+)-participating nanocluster displayed the strongest fluorescence intensity in both solution and crystal states.Atomic-level structure–property correlations were investigated to rationalize the PL comparisons.Overall,this work offers a new perspective for regulating the PL of metal nanoclusters via restricting their molecular motions,hopefully providing insight into the fabrication of highly emissive metal nanoclusters and cluster-based nanomaterials.
基金supported by the Natural Science Foundation of China(Grant Nos.42088101 and 42375163)the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2021B0301030007)the specific research fund of The Innovation Platform for Academicians of Hainan Province(Grant No.YSPTZX202143)。
文摘In Earth system modeling,the land surface is coupled with the atmosphere through surface turbulent fluxes.These fluxes are computed using mean meteorological variables between the surface and a reference height in the atmosphere.However,the dependence of flux computation on the reference height,which is usually set as the lowest level in the atmosphere in Earth system models,has not received much attention.Based on high-resolution large-eddy simulation(LES)data under unstable conditions,we find the setting of reference height is not trivial within the framework of current surface layer theory.With a reasonable prescription of aerodynamic roughness length(following the setting in LESs),reference heights near the top of the surface layer tend to provide the best estimate of surface fluxes,especially for the momentum flux.Furthermore,this conclusion for the sensible heat flux is insensitive to the ratio of roughness length for momentum versus heat.These results are robust,whether using the classical or revised surface layer theory.They provide a potential guide for setting the proper reference heights for Earth system modeling and can be further tested in the near future using observational data from land–atmosphere feedback observatories.
文摘The production of C_(2)H_(3)Cl from CH_(3)Cl(MCTV)represents a promising non-petroleum route for synthesizing C_(2)alkenes from C_(1)molecules.Exploration of new MCTV catalysts is crucial for advancing sustainable chemical production.In this study,we present NaVO_(3)as a surface-confined coupling center for·CH_(2)Cl radicals,demonstrating its superior performance in the selective coupling of methyl chloride to synthesize vinyl chloride.By incorporating NaVO_(3)onto the surface of CeO_(2),the catalyst enables effective capture of·CH_(2)Cl radicals during the CH_(3)Cl oxidative pyrolysis and their subsequent conversion into C_(2)H_(3)Cl.We experimentally validate the capability of highly dispersed Na-VO_(3)to controllably couple·CH_(2)Cl radicals through in-situ synchrotron-based vacuum ultraviolet photoionization mass spectrometry.The results demonstrate that the dispersion of NaVO_(3)on the catalyst surface has a considerable impact on the reaction efficiency of·CH_(2)Cl radicals and the overall MCTV performance.This discovery holds substantial implications for the controlled C_(1)radical transformation and provides a guidance for the design of catalysts for sustainable production of C_(2)H_(3)Cl.
文摘We report a non-destructive characterization of planar two-dimensional （2D） photonic crystals （PhCs） made in silicon on insulator （SOI） wafers using ellipsometric or Fourier transformed infrared （FTIR） spectroscope. At large wavelengths, devices behave as homogeneous isotropic materials defined by an effective filling factor. The experimental results related to the PhC limited dimensions confirm this characterization.
基金supported by the Zhejiang Provincial Natural Science Foundation of China(No.LGF20C050001)the National Nature Science Foundation of China(No.61805213)。
文摘We use the method of discrete dipole approximation with surface interaction to construct a model in which a plurality of nanoparticles is arranged on the surface of BK7 glass. Nanoparticles are in air medium illuminated by evanescent wave generated from total internal reflection. The effects of the wavelength, the polarization of the incident wave, the number of nanoparticles and the spacing of multiple nanoparticles on the field enhancement and extinction efficiency are calculated by our model. Our work could pave the way to improve the field enhancement of multiple nanoparticles systems.
基金supported by the National Natural Science Foundation of China(Nos.U1304608 and 61774053)the Project of Henan Provincial Department of Science and Technology(No.182102410047)the Program of Henan Polytechnic University(No.B2014-020)。
文摘Photoluminescence(PL)was investigated as functions of the excitation intensity and temperature for a coupling surface quantum dots(SQDs)structure which consists of one In_(0.3)Ga_(0.7)As SQDs layer being stacked on multi-layers of In_(0.3)Ga_(0.7)As buried quantum dots(BQDs).Accompanied by considering the localized excitons effect induced by interface fluctuation,carrier transition between BQDs and SQDs were analyzed carefully.The PL measurements confirm that there is a strong carrier transition from BQDs to SQDs and this transition leads to obvious different PL characteristics between BQDs and SQDs.These results are useful for future application of SQDs as surface sensitive sensors.
文摘High performance electromechanical equipment is widely used in various fields, such as national defense, industry and so on [ 1]. In addition, the technical level of high performance electromechanical equipment is the embodiment of the national level of science and technology.
基金Supported by National Special Cooperation Project of International Science and Technology of China(Grant No.S2013HR0021L)Key Project of Fujian Provincial Science and Technology of China(Grant No.2012H0034)
文摘The main methods of the existing multi-spiral surface geometry modeling include spatial analytic geometry algorithms, graphical method, interpolation and approximation algorithms. However, there are some shortcomings in these modeling methods, such as large amount of calculation, complex process, visible errors, and so on. The above methods have, to some extent, restricted the design and manufacture of the premium and high-precision products with spiral surface considerably. This paper introduces the concepts of the spatially parallel coupling with multi-spiral surface and spatially parallel coupling body. The typical geometry and topological features of each spiral surface forming the multi-spiral surface body are determined, by using the extraction principle of datum point cluster, the algorithm of coupling point cluster by removing singular point, and the ＂spatially parallel coupling＂ principle based on the non-uniform B-spline for each spiral surface. The orientation and quantitative relationships of datum point cluster and coupling point cluster in Euclidean space are determined accurately and in digital description and expression, coupling coalescence of the surfaces with multi-coupling point clusters under the Pro/E environment. The digitally accurate modeling of spatially parallel coupling body with multi-spiral surface is realized. The smooth and fairing processing is done to the three-blade end-milling cutter＇s end section area by applying the principle of spatially parallel coupling with multi-spiral surface, and the alternative entity model is processed in the four axis machining center after the end mill is disposed. And the algorithm is verified and then applied effectively to the transition area among the multi-spiral surface. The proposed model and algorithms may be used in design and manufacture of the multi-spiral surface body products, as well as in solving essentially the problems of considerable modeling errors in computer graphics and engineering in multi-spiral surface＇s connection available with approximate methods or graphical methods.
基金The Shandong Provincial Natural Science Foundation under contract No.ZR2021YQ28the Provincial College Student Innovation Training Project under contract No.S202110446040。
文摘This study investigated the seasonal variation in the atmospheric response to oceanic mesoscale eddies in the North Pacific Subtropical Countercurrent(STCC)and its mechanism,based on satellite altimetric and reanalysis datasets.Although mesoscale eddy in the study area is more active in summer,the sea surface temperature(SST)anomaly associated with mesoscale eddies is more intense and dipolar in winter,which is largely due to the larger background SST gradient.Similarly,the impact of the oceanic eddy on sea surface wind speed and heat flux is strongest in winter,whereas its effect on precipitation rate is more significant in summer.The study revealed that the SST gradient in STCC could impact the atmosphere layer by up to 800 h Pa(900 h Pa)in boreal winter(summer)through the dominant vertical mixing mechanism.Moreover,the intensity of the SST gradient causes such seasonal variation in mesoscale air-sea coupling in the study region.In brief,a stronger(weaker)background SST gradient field in wintertime(summertime)leads to a larger(smaller)eddy-induced SST anomaly,thus differently impacting atmosphere instability and transitional kinetic energy flux over oceanic eddies,leading to seasonal variation in mesoscale air-sea coupling intensity.
基金Financial support from the National Natural Science Foundation of China (Nos. 21874110, 21804098, 21974117 and 22274137)the Science and Technology Program of Fujian Province (No. 2022Y4008)
文摘Simultaneous acquisition of fluorescence property and refractive index using a single surface plasmon coupled emission(SPCE)measurement has been achieved,thus achieving synchronicity in real time.The SPCE sensor was employed for monitoring the adsorption of volatile organic compounds(VOCs)by dyeencapsulated metal-organic frameworks(Dye@MOFs).Refractive index can reveal surface molecular adsorption and the fluorescence with information on refractive index can provide a comprehensive analysis of the adsorption events of VOCs on the interface.Meantime,the signal intensity can be amplified by combining the responses caused by changes in refractive index and the fluorescence property in parallel.This all-in-one method opens up a route to monitoring multiple processes simultaneously occurring on the interface.
基金Financial support from the National Natural Science Foundation of China(Nos.21874110,21375111,21505109,21521004 and 21804098)the Fund of the Ministry of Education of China(No. IRT17R66)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(No.201802104)
文摘The obvious enhancement effect of magnetic nanoparticles(MNPs) introduced in Cr/Co/Cr/Au substrate on the pulsed magnetic field-modulated surface plasmon coupled emission(SPCE) was investigated,and the observed enhancement factor was 4 comparing with the magnetic field modulated SPCE without MNPs.This is the new observation for the magnetic field modulated SPCE,and this method was designed as a biosensor,which to our knowledge,is the first application of magnetic field-modulated SPCE in biosensing and detection field.This strategy is a universal approach to increase the fluorescence signal and helps to build the new SPCE based stimulus-response system.
文摘Water stored as part of the land surface is lost to evapotranspiration and runoff on different time scales, and the partitioning between these time scales is important for modeling soil water in a climate model. Different time scales are imposed on evapotranspiration primarily because it is derived from different reservoirs with different storage capacities, from the very rapid evaporation of canopy stores to the slow removal by transpiration of rooting zone soil moisture. Runoff likewise ranges in time scale from rapid surface terms to the slower base-flow. The longest time scale losses of water determine the slow variation of soil moisture and hence the longer time scale effects of soil moisture on precipitation. This paper shows with a simple analysis how shifting the partitioning of evapotranspiration between the different reservoirs affects the variability of soil moisture and precipitation. In particular, it is concluded that a shift to shorter time scale reservoirs shifts the variance of precipitation from that which is potentially predictable to unpredictable.
基金Financial support and data source for this work is provided by the US Environmental Protection Agency(No.OR13810-001.04 A10-0223-S001-A02)Guangzhou Environmental Protection Bureau(No.x2hj B2150020)+4 种基金the project of an integrated modeling and filed observational verification on the deposition of typical industrial point-source mercury emissions in the Pearl River Deltapartly supported by the funding of Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control(No.2011A060901011)the project of Atmospheric Haze Collaboration Control Technology Design(No.XDB05030400)from the Chinese Academy of Sciencesthe Ministry of Environmental Protection's Special Funds for Research on Public Welfare(No.201409002)Partly financial support is also provided by the Guangdong Provincial Department of Science and Technology,the project of demonstration research of air quality management cost-benefit analysis and attainment assessments technology(No.2014A050503019)
文摘This article describes the development and application of a streamlined air control and response modeling system with a novel response surface modeling-linear coupled fitting method and a new module to provide streamlined model data for PM_（2.5） attainment assessment in China.This method is capable of significantly reducing the dimensions required to establish a response surface model,as well as capturing more realistic response of PM_（2.5） to emission changes with a limited number of model simulations.The newly developed module establishes a data link between the system and the Software for Model Attainment Test—Community Edition（SMAT-CE）,and has the ability to rapidly provide model responses to emission control scenarios for SMAT-CE using a simple interface.The performance of this streamlined system is demonstrated through a case study of the Yangtze River Delta（YRD） in China.Our results show that this system is capable of reproducing the Community Multi-Scale Air Quality（CMAQ） model simulation results with maximum mean normalized error 〈 3.5%.It is also demonstrated that primary emissions make a major contribution to ambient levels of PM_（2.5） in January and August（e.g.,more than50%contributed by primary emissions in Shanghai）,and Shanghai needs to have regional emission control both locally and in its neighboring provinces to meet China＇s annual PM_（2.5）National Ambient Air Quality Standard.The streamlined system provides a real-time control/response assessment to identify the contributions of major emission sources to ambient PM_（2.5）（and potentially O_3 as well） and streamline air quality data for SMAT-CE to perform attainment assessments.
基金Project supported by the National Natural Science Foundation of China(Grant No.60708014)the Science Foundation for Postdoctorate of China(Grant No.2004035083)+2 种基金the Natural Science Foundation of Hunan Province of China(Grant No.06JJ2034)the Excellent Doctorate Dissertation Foundation of Central South University(Grant No.2008yb039)the Hunan Provincial Innovation Foundation for Postgraduate(Grant No.CX2009B029)
文摘Based on the finite difference time domain method, we investigated theoretically the optical properties and the plasmonic interactions between a gold film perforated with periodic sub-wavelength holes and a thin gold film. We showed that the plasmon resonant energies and intensities depend strongly on the thicknesses of the two films and the lattice constant. Based on the distributions of normal electric field component Ez, tangential electric field component Ey and total energy, we showed that the optical transmission is due to the collaboration of the localized waveguide resonance, the surface plasmon resonance and the coupling of the fiat-surface plasmon of the two layers.
基金National Natural Science Foundation of China(NSFC)(61571399)“The Belt and Road”International Cooperation of Zhejiang Province,China(2015C04005)
文摘We propose a design for efficient end-fire coupling of surface plasmon polaritons in a metal-insulator-metal(MIM) waveguide with an optical fiber as part of a simple photoplastic connector. The design was analyzed and optimized using the three-dimensional finite-difference time-domain method. The calculated excitation efficiency coefficient of the waveguide is 83.7%(-0.77 dB) at a wavelength of 405 nm. This design enables simple connection of an optical fiber to a MIM waveguide and highly efficient local excitation of the waveguide.Moreover, the length of the metallic elements of the waveguide, and thus the dissipative losses, can be reduced.The proposed design may be useful in plasmonic-type waveguide applications such as near-field investigation of live cells and other objects with super-resolution.
基金This study was supported by National Key Research and Development Program of China （2016YFA0601801）, the State Key Program of National Natural Science Foundation of China （41530424）, National Program on Global Change and Air-Sea Interactions, State Oceanic Administration （SOA） （GASI-IPOVAI-03）, and the National Natural Science Foundation of China （41305121）. We sincerely thank two anonymous reviewers whose comments improved the paper.
文摘Based on observations and Coupled Model lntercomparison Project Phase 5 （CMIP5） results, multidecadal variations and trends in annual mean surface air temperature anomalies （SATa） at global, hemispheric, and hemispheric land and ocean scales in the past and under the future scenarios of two representative concentration pathways （RCPs） are analyzed. Fifteen models are selected based on their performances in capturing the temporal variability, long-term trend, multidecadal variations, and trends in global annual mean SATa. Observational data analysis shows that the multidecadal variations in annual mean SATa of the land and ocean in the northern hemisphere （NH） and of the ocean in the southern hemisphere （SH） are similar to those of the global mean, showing an increase during the 1900-1944 and 1971-2000 periods, and flattening or even cooling during the 1945-1970 and 2001-2013 periods. These observed characteristics are basically reproduced by the models. However, SATa over SH land show an increase during the 1945-1970 period, which differs from the other hemispheric scales, and this feature is not captured well by the models. For the recent hiatus period （2001-2013）, the projected trends of BCC-CSM1-1-m, CMCC-CM, GFDL-ESM2M, and NorESM1-ME at the global and hemispheric scales are closest to the observations based on RCP4.5 and RCP8.5 scenarios, suggesting that these four models have better projection capability in SATa. Because these four models are better at simulating and projecting the multidecadal trends of SATa, they are selected to analyze future SATa variations at the global and hemispheric scales during the 2006-2099 period. The selected multi-model ensemble （MME） projected trends in annual mean SATa for the globe, NH, and SH under RCP4.5 （RCP8.5） are 0.17 （0.29） ℃, 0.22 （0.36） ℃, and 0.11 （0.23） ℃-decade-1 in the 21st century, respectively. These values are significantly lower than the projections of CMIP5 MME without model selection.
基金National Natural Science Foundation of China(NSFC)(11274230,11574206)Basic Research Program of the Committee of Science and Technology of Shanghai(14JC1491700)
文摘Cavity optomechanics is applied to study the coupling behavior of interacting molecules in surface plasmon systems driven by two-color laser beams. Different from the traditional force–distance measurement, due to a resonant frequency shift or a peak splitting on the probe spectrum, we have proposed a convenient method to measure the van der Waals force strength and interaction energy via nonlinear spectroscopy. The minimum force value can reach approximately 10^(-15) N, which is 3 to 4 orders of magnitude smaller than the widely applied atomic force microscope(AFM). It is also shown that two adjacent molecules with similar chemical structures and nearly equal vibrational frequencies can be easily distinguished by the splitting of the transparency peak. Based on this coupled optomechanical system, we also conceptually design a tunable optical switch by van der Waals interaction. Our results will provide new approaches for understanding the complex and dynamic interactions inmolecule–plasmon systems.
文摘The ionic and neutral state potential energy surfaces (PESs) of Na+I 2 collision system have been calculated on QCISD(T) level by using ab initio method. The location and depth of the potential well, the collision radius and their fine structures have been analyzed at the equilibrium geometry of I 2 molecule. The electronic transfer probabilities are also calculated in terms of Landau Zener model. The lifetime of scattering resonance state is evaluated by the uncertainty principle. All the results have been compared with those obtained according to the Aten Lanting Los PES and Feng's PES.
文摘In this paper, we have analyzed the processes of temporal and spatial development in the interaction be- tween the Northern Oscillation and the sea surface temperature of the cquatorial Pacific. It is revealed that between them there is a closed negative feedback process and the whole period including their influence, feedback and adjustment to each other is about 3.5 years. Furthermore, we have discussed the physical processes responsible for various links between the Northern Oscillation and the sea surface temperature of the equatorial Pacific. A physical model on 3.5-year coupled oscillation caused by the air-sea interaction in the tropical Pacific is postulated.
