Low-temperature CO oxidation has attracted extensive interest in heterogeneous catalysis because of the potential applications in fuel cells,air cleaning,and automotive emission reduction.In the present study,theoreti...Low-temperature CO oxidation has attracted extensive interest in heterogeneous catalysis because of the potential applications in fuel cells,air cleaning,and automotive emission reduction.In the present study,theoretical investigations have been performed using density functional theory to elucidate the crystal plane effect and structure sensitivity of Co3O4 nano-catalysts toward catalyzing CO oxidation.It is shown that the surface Co–O ion pairs are the active site for CO oxidation on the Co3O4 surface.Because of stronger CO adsorption and easier removal of lattice oxygen ions,the Co3O4(011)surface is shown to be more reactive for CO oxidation than the Co3O4(001)surface,which is consistent with previous experimental results.By comparing the reaction pathways at different sites on each surface,we have further elucidated the nature of the crystal plane effect on Co3O4 surfaces and attributed the reactivity to the surface reducibility.Our results suggest that CO oxidation catalyzed by Co3O4 nanocrystals has a strong crystal plane effect and structure sensitivity.Lowering the vacancy formation energy of the oxide surface is key for high CO oxidation reactivity.展开更多
When a seismic wave propagates through subsurface viscoelastic media,the formation absorbs the high-frequency energy of the seismic wave more strongly than the low-frequency energy.As the depth and the off set increas...When a seismic wave propagates through subsurface viscoelastic media,the formation absorbs the high-frequency energy of the seismic wave more strongly than the low-frequency energy.As the depth and the off set increase,the diff erence between the logarithmic spectral areas with high and low frequencies gradually increases.Based on this seismic wave characteristic,we have developed a novel Q-estimation method based on logarithmic spectral area diff erence of high and low frequencies(referred to as the LSAD_LH method).In this paper,we derive the theoretical relationship between the Q value and difference of logarithmic spectral areas with high and low frequencies and prove the applicability of the LSAD_LH method using a single-layer medium numerical model.To verify the sensitivity of the LSAD_LH method to bandwidth selection and noise,we compare the LSAD_LH method with two credible methods—the logarithmic spectral ratio(LSR)and logarithmic spectral area diff erence(LSAD)methods using a synthetic model containing the random noise.The results demonstrate that the LSAD_LH method is not highly dependent on bandwidth,and in terms of noise immunity,it is signifi cantly better than the LSR method and has the same advantages as the LSAD method.To further highlight the advantages of the LSAD_LH method,we apply the LSAD_LH and LSAD methods to the vertical seismic profi ling(VSP)numerical simulation of the multilayer media and the fi eld zero-off set VSP data.The application of the two cases proves the applicability of the LSAD_LH method and the accuracy of the high Q-value estimation relative to the LSAD method.Moreover,via the transmission coeffi cient,the LSAD_LH method overcomes the weakness of the LSAD method.展开更多
Concentration gradient induced Rayleigh convection can influence effectively interracial mass transfer processes, but the convection phenomena are known as mesoscopic and complex. In order to investigate this phenomen...Concentration gradient induced Rayleigh convection can influence effectively interracial mass transfer processes, but the convection phenomena are known as mesoscopic and complex. In order to investigate this phenomenon, a two-equation Lattice Boltzmann Method (LBM) is proposed to simulate the velocity and the concentra-tion distributions of Rayleigh convection generated in the CO2 absorptlon into ethanol liquid.The simulated results on velocity distributions are experimentally verified by PIV (particle image velocimetry technique) measurements. In order to simplify the analysis, the convection in the simulation as well as in the experiment, the Rayleigh convection was manipulated into a single down flow pattern, The simulated results show that the concentration contours agree qualitatively with the schlieren images in the literature. The experimental and simulated results show that theRayleigh convection under investigation is dominated by the flow in the downward direction and impels exchange of the liquid between the interfacial vicinity and the liquid bulk promoting the renewal of interfacial liquid, and hence enhances mass transfer. The comparison between the simulated and experimental results demonstrated that the proposed LBM is a promising alternative for simulating mass transfer induced Rayleigh convection.展开更多
In the present paper, the spectrums of off-diagonal infinite-dimensional Hamiltonian operators are studied. At first, we prove that the spectrum, the continuous-spectrum, and the union of the point-spectrum and residu...In the present paper, the spectrums of off-diagonal infinite-dimensional Hamiltonian operators are studied. At first, we prove that the spectrum, the continuous-spectrum, and the union of the point-spectrum and residual- spectrum of the operators are symmetric with respect to real axis and imaginary axis. Then for the purpose of reducing the dimension of the studied problems, the spectrums of the operators are expressed by the spectrums of the product of two self-adjoint operators in state spac,3. At last, the above-mentioned results are applied to plane elasticity problems, which shows the practicability of the results.展开更多
The constructive or destructive spectral interference between the molecular groups oriented up and down at the interface in the sum-frequency generation (SFG) spectra provides a direct measurement of the absolute or...The constructive or destructive spectral interference between the molecular groups oriented up and down at the interface in the sum-frequency generation (SFG) spectra provides a direct measurement of the absolute orientation of these molecular groups. This simple approach can be employed to interrogate absolute molecular orientations other than using the complex absolute phase measurement in the SFG studies. We used the -CN group in the p-cyanophenol (PCP) molecule as the internal phase standard, and we measured the phases of the SFG fields of the -CN groups in the 3,5-dimethyl-4-hydroxy-benzonitrile (35DMHBN) and 2,6-dimethyl-4-hydroxy-benzonitrile (26DMHBN) at the air/water interface by measuring the SFG spectra of the aqueous surfaces of the mixtures of the PCP, 35DMHBN, and 26DMHBN solutions. The results showed that the 35DMHBN had its -CN group pointing into the aqueous phase; while the 26DMHBN, similar to the PCP, had its -CN group pointing away from the aqueous phase. The tilt angles of the -CN group for both the 35DMHBN and 26DMHBN molecules at the air/water interface were around 25°-45° from the interface normal. These results provided insights on the understanding of the detailed balance of the competing factors, such as solvation of the polar head groups, hydrogen bonding and hydrophobic effects, etc., on influencing the absolute molecular orientation at the air/water interface.展开更多
A non-relativistic microscopic mean field theory of finite nuclei is investigated where the nucleus is described as a collection of nucleons and delta resonances. The ground state properties of 90Zr nucleus have been ...A non-relativistic microscopic mean field theory of finite nuclei is investigated where the nucleus is described as a collection of nucleons and delta resonances. The ground state properties of 90Zr nucleus have been investigated at equilibrium and large amplitude compression using a realistic effective baryon-baryon Hamiltonian based on Reid Soft Core (RSC) potential. The sensitivity of the ground state properties is studied, such as binding energy, nuclear radius, radial density distribution, and single particle energies to the degree of compression. It is found that the most of increasing in the nuclear energy generated under compression is used to create the massive Δ particles. For 90Zr nucleus under compression at 2.5 times density of the normal nuclear density, the excited nucleons to Δ 's are increased sharply up to 14% of the total number of constituents. This result is consistent with the values extracted from relativistic heavy-ion collisions. The single particle energy levels are calculated and their behaviors under compression are examined too. A good agreement between results with effective Hamiltonian and the phenomenologieal shell model for the low lying single-particle spectra is obtained. A considerable reduction in compressibility for the nucleus, and softening of the equation of state with the inclusion of the Δ's in the nuclear dynamics are suggested by the results.展开更多
We consider the covalence characters of the 3d electron with the eg orbital freedoms and put forward a new mechanism of the orbital ordering (00) based on the direct coulomb repulsion in this article. The results sh...We consider the covalence characters of the 3d electron with the eg orbital freedoms and put forward a new mechanism of the orbital ordering (00) based on the direct coulomb repulsion in this article. The results show that the orbital-orbital interaction (OO-I) between the adjacent ions in 180-degree configuration is dominated by the superexchange energy accompanied by a weak orbital-spin coupling, and the OO-I in 90-degree configuration is monitored by the oxygen on-site coulomb repulsion. The ferro-OO is the stable ground state for the one-dimensional chain in the case of the 90-degree configuration.展开更多
In the context of topcolor-assisted technicolor (TC2) model, we study the charged and neutral top-pions production process γγ →W+ ∏t-∏t^0. We find that the production cross section is larger than that of the p...In the context of topcolor-assisted technicolor (TC2) model, we study the charged and neutral top-pions production process γγ →W+ ∏t-∏t^0. We find that the production cross section is larger than that of the process γγ→ W+ H-H in the minimal supersymmetric standard model. With reasonable values of the parameters in the TC2 model, the cross section can reach the level of a few fb. Furthermore, the flavor-changing (FC) decay mode ∏t^0 → te^- is the best channel to detect the neutral top-pion due to the clean SM background. With a large number of events and the clean background, the neutral top-pion should be observable at future linear colliders operating in γγ mode at the TeV energy scale.展开更多
The contribution of the resonant continuum to pairing correlations is investigated in the relativistic mean field theory plus Bardeen–Cooper–Schrieffer (BCS) approximation with a constant pairing strength. The reson...The contribution of the resonant continuum to pairing correlations is investigated in the relativistic mean field theory plus Bardeen–Cooper–Schrieffer (BCS) approximation with a constant pairing strength. The resonance states with their widths in the continuum are considered explicitly. The numerical study is performed in an effective Lagrangian with the parameter set NLSH for neutron-rich nucleus <SUP>84</SUP>Ni. The results show that the effect of the proper treatment of the resonant continuum on pairing correlations for nucleus close to neutron drip line is important. It is found that the problem of an unphysical particle gas could be overcome when the pairing correlation is performed by using the resonant states instead of the discretized states in the continuum.展开更多
In order to improve the thermal environment of high-temperature heading face,moisture content of supply air is reduced by dehumidification, and the relative humidity ofenvironment air of the heading face is also decre...In order to improve the thermal environment of high-temperature heading face,moisture content of supply air is reduced by dehumidification, and the relative humidity ofenvironment air of the heading face is also decreased.First, according to the coefficient ofperformance of dehumidifier, the capacity of dehumidification was calculated.Second, inthe engineering example of the heading face, quantitative changes of WBGT (Wet BulbGlobe Temperature) were compared between with dehumidification and without dehumidification.Based on WBGT standards, the thermal comfort of high-temperature environmentof heading face was evaluated between with dehumidification and without handling.Reducingthe relative humidity of airflow through dehumidification, the thermal comfort of ahigh-temperature environment of heading face can improve greatly.Even if dry bulb temperatureof airflow is not decreased, the thermal comfort of heading face environment isalso improved to some extent.展开更多
The effects of sintering atmosphere on the properties of symmetric TiO2 membranes are studied with regard to sintering behavior, porosity, mean pore size, surface comPosition. and surface charge properties. The exerim...The effects of sintering atmosphere on the properties of symmetric TiO2 membranes are studied with regard to sintering behavior, porosity, mean pore size, surface comPosition. and surface charge properties. The exerimental results show that the symmetric TiO2 membranes display better sintering activity in the air than in argon, and the mean pore diameters and porosities of the membrane sintered in argon are higher than those of the membrane sintered in the air at the same temperature. The surface compositions of the symmetric TiO2 membrane sintered in the air and in argon at different temperatures, as studied by X-ray photoelectron spectroscopy, are discussed in terms of their chemical composition, with particular emphasis on the valence state of the titanium ions. The correlation between the valence state of the titanium ions at the surface and the surface charge properties is examined.It is found that the presence of Ti^3+, introduced at the surface of the symmetric TiO2 membranes by sintering in a lower partial pressure of oxygen, is related to a significant decrease in the isoelectric point. TiO2 with Ti^4+ at the interface has an isoelectric point of 5.1, but the non-stoichiometric TiO2-x with Ti^3+ at the interface has a lower isoelectric point of 3.6.展开更多
Polyethersulfone(PES)film with regular microporous structure was formed using dichloromethane as the solvent via water vapor induced phase separation(VIPS).The effects of solution concentration,atmospheric humidity an...Polyethersulfone(PES)film with regular microporous structure was formed using dichloromethane as the solvent via water vapor induced phase separation(VIPS).The effects of solution concentration,atmospheric humidity and temperature,as well as molecular weight of PES on the surface morphology of the polymer film were investigated.The surface morphology characterized by SEM showed that the pore size reduced as the solution concentration increased.There was an optimum range of relative humidity for the formation of regular pore structure, which was from 60%to 90%at concentration of 20 g·L-1 and 20°C.With the atmospheric temperature varied from 20 to 30°C,the pore became larger and the space between pores increased.The pore size in the PES film with low molecular weight was smaller than that with high molecular weight.展开更多
The geodesic acoustic mode (GAM), first predicted by Winsor, Johnson and Dawson in an attempt to explain some experimentally observed low frequency oscillations in stellarators, is a special electrostatic fluid mode...The geodesic acoustic mode (GAM), first predicted by Winsor, Johnson and Dawson in an attempt to explain some experimentally observed low frequency oscillations in stellarators, is a special electrostatic fluid mode with low mode number and coupled with the so-called geodesic curvature of a toroidally confined plasma. The recent on this mode are due to the close relevance of the stabi- lization of drift turbulence by both the zonal flow and the GAM. Previously, the GAM was illustrated in very simple geometries,展开更多
Previous theoretical studies have shown that dayside chorus can produce butterfly distribution of energetic electrons in the Earth's radiation belts by preferentially accelerating medium pitch angle electrons, but th...Previous theoretical studies have shown that dayside chorus can produce butterfly distribution of energetic electrons in the Earth's radiation belts by preferentially accelerating medium pitch angle electrons, but this requires the further confirmation from high- resolution satellite observation. Here, we report correlated Van Allen Probes data on wave and particle during the 1 I-13 April, 2014 geomagnetic storm. We find that a butterfly pitch angle distribution of relativistic electrons is formed around the location L = 4.52, corresponding to the presence of enhanced dayside chorus. Using a Gaussian distribution fit to the observed chorus spectra, we calculate the bounce-averaged diffusion rates and solve two-dimensional Fokker-Planck equation. Numerical results demonstrate that acceleration by dayside chorus can yield the electron flux evolution both in the energy and butterfly pitch angle distribution comparable to the observation, providing a further evidence for the formation of butterfly distribution of relativistic electrons driven by very low frequency (VLF) plasma waves.展开更多
In this study,we propose valley phononic crystals that consist of a hexagonal aluminum plate with six chiral arrangements of ligaments.Valley phononic crystals were introduced into a topological insulator(TI)system to...In this study,we propose valley phononic crystals that consist of a hexagonal aluminum plate with six chiral arrangements of ligaments.Valley phononic crystals were introduced into a topological insulator(TI)system to produce topologically protected edge waves(TPEW s)along the topological interfaces.The implementation of chiral topological edge states is different from the implementation of topological edge states of systems with symmetry.Unlike the conventional breaking of mirror symmetry,a new complete band with topological edge modes gap was opened up at the Dirac point by tuning the difference in lengths of the ligaments in the chiral unit cells.We investigated the dispersion properties in chiral systems and applied the dispersion properties to waveguides on the interfaces to achieve designable route systems.Furthermore,we simulated the robust propagation of TPEWs in different routes and demonstrated their immunity to backscattering at defects.Finally,the existence of the valley Hall effect in chiral systems was demonstrated.The study findings may lead to the further study of the topological states of chiral materials.展开更多
In this work, we reported the synthesis of twodimensional spinel structure of ultrathin Co2AlO4 nanosheets via dealloying and subsequent annealing processes. Oxygen vacancy defects were further introduced into Co2AlO4...In this work, we reported the synthesis of twodimensional spinel structure of ultrathin Co2AlO4 nanosheets via dealloying and subsequent annealing processes. Oxygen vacancy defects were further introduced into Co2AlO4 nanosheets by a mild solvothermal reduction method, resulting in large electrochemical surface area and high active site densities, making the related Co atoms get electrons, and producing more empty orbitals. The positive charge of Co and Al atoms adjacent to the O vacancies in VO-rich Co2AlO4 reduced significantly, that is, more electrons are concentrated on the Co and Al atoms. Those electrons closed to the Fermi level have a promoting effect during the H2O activation. As a result, the obtained ultrathin Co2AlO4 nanosheets with oxygen vacancies show a low overpotential of 280 m V at the current density of 10 mA cm^-2 and a small Tafel slope of70.98 m V dec^-1. Moreover, it also displays a remarkable stability in alkaline solution, which is superior to most of the reported Co3O4 electrocatalysts. The present work paves a new way to achieve efficient new energetic materials for sustainable community.展开更多
基金supported by the National Basic Research Program of China(2011CB932401)the National Natural Science Foundation of China(21221062)~~
文摘Low-temperature CO oxidation has attracted extensive interest in heterogeneous catalysis because of the potential applications in fuel cells,air cleaning,and automotive emission reduction.In the present study,theoretical investigations have been performed using density functional theory to elucidate the crystal plane effect and structure sensitivity of Co3O4 nano-catalysts toward catalyzing CO oxidation.It is shown that the surface Co–O ion pairs are the active site for CO oxidation on the Co3O4 surface.Because of stronger CO adsorption and easier removal of lattice oxygen ions,the Co3O4(011)surface is shown to be more reactive for CO oxidation than the Co3O4(001)surface,which is consistent with previous experimental results.By comparing the reaction pathways at different sites on each surface,we have further elucidated the nature of the crystal plane effect on Co3O4 surfaces and attributed the reactivity to the surface reducibility.Our results suggest that CO oxidation catalyzed by Co3O4 nanocrystals has a strong crystal plane effect and structure sensitivity.Lowering the vacancy formation energy of the oxide surface is key for high CO oxidation reactivity.
基金National Nature Science Foundation of China(Grant No.U1562110)。
文摘When a seismic wave propagates through subsurface viscoelastic media,the formation absorbs the high-frequency energy of the seismic wave more strongly than the low-frequency energy.As the depth and the off set increase,the diff erence between the logarithmic spectral areas with high and low frequencies gradually increases.Based on this seismic wave characteristic,we have developed a novel Q-estimation method based on logarithmic spectral area diff erence of high and low frequencies(referred to as the LSAD_LH method).In this paper,we derive the theoretical relationship between the Q value and difference of logarithmic spectral areas with high and low frequencies and prove the applicability of the LSAD_LH method using a single-layer medium numerical model.To verify the sensitivity of the LSAD_LH method to bandwidth selection and noise,we compare the LSAD_LH method with two credible methods—the logarithmic spectral ratio(LSR)and logarithmic spectral area diff erence(LSAD)methods using a synthetic model containing the random noise.The results demonstrate that the LSAD_LH method is not highly dependent on bandwidth,and in terms of noise immunity,it is signifi cantly better than the LSR method and has the same advantages as the LSAD method.To further highlight the advantages of the LSAD_LH method,we apply the LSAD_LH and LSAD methods to the vertical seismic profi ling(VSP)numerical simulation of the multilayer media and the fi eld zero-off set VSP data.The application of the two cases proves the applicability of the LSAD_LH method and the accuracy of the high Q-value estimation relative to the LSAD method.Moreover,via the transmission coeffi cient,the LSAD_LH method overcomes the weakness of the LSAD method.
基金Supported by the National Natural Science Foundation of China (20736005).
文摘Concentration gradient induced Rayleigh convection can influence effectively interracial mass transfer processes, but the convection phenomena are known as mesoscopic and complex. In order to investigate this phenomenon, a two-equation Lattice Boltzmann Method (LBM) is proposed to simulate the velocity and the concentra-tion distributions of Rayleigh convection generated in the CO2 absorptlon into ethanol liquid.The simulated results on velocity distributions are experimentally verified by PIV (particle image velocimetry technique) measurements. In order to simplify the analysis, the convection in the simulation as well as in the experiment, the Rayleigh convection was manipulated into a single down flow pattern, The simulated results show that the concentration contours agree qualitatively with the schlieren images in the literature. The experimental and simulated results show that theRayleigh convection under investigation is dominated by the flow in the downward direction and impels exchange of the liquid between the interfacial vicinity and the liquid bulk promoting the renewal of interfacial liquid, and hence enhances mass transfer. The comparison between the simulated and experimental results demonstrated that the proposed LBM is a promising alternative for simulating mass transfer induced Rayleigh convection.
基金supported by the National Natural Science Foundation of China under Grant No.10562002the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No.20070126002+1 种基金the Natural Science Foundation of Inner Mongolia under Grant No.200508010103the Inner Mongolia University Scientific Research Starting Foundation for Talented Scholars under Grant No.207066
文摘In the present paper, the spectrums of off-diagonal infinite-dimensional Hamiltonian operators are studied. At first, we prove that the spectrum, the continuous-spectrum, and the union of the point-spectrum and residual- spectrum of the operators are symmetric with respect to real axis and imaginary axis. Then for the purpose of reducing the dimension of the studied problems, the spectrums of the operators are expressed by the spectrums of the product of two self-adjoint operators in state spac,3. At last, the above-mentioned results are applied to plane elasticity problems, which shows the practicability of the results.
基金Ⅵ. ACKNOWLEDGMENTS Hong-fei Wang thanks the support by the National Natural Science Foundation of China (No.20373076, No.20425309, and No.20533070) and the Ministry of Science and Technology of China (No.2007CB815205). Zhi-feng Cui thanks the support by the Natural Science Foundation of China (No.10674002) and the Natural Science Foundation of Anhui Province (No.ZD2007001-1).
文摘The constructive or destructive spectral interference between the molecular groups oriented up and down at the interface in the sum-frequency generation (SFG) spectra provides a direct measurement of the absolute orientation of these molecular groups. This simple approach can be employed to interrogate absolute molecular orientations other than using the complex absolute phase measurement in the SFG studies. We used the -CN group in the p-cyanophenol (PCP) molecule as the internal phase standard, and we measured the phases of the SFG fields of the -CN groups in the 3,5-dimethyl-4-hydroxy-benzonitrile (35DMHBN) and 2,6-dimethyl-4-hydroxy-benzonitrile (26DMHBN) at the air/water interface by measuring the SFG spectra of the aqueous surfaces of the mixtures of the PCP, 35DMHBN, and 26DMHBN solutions. The results showed that the 35DMHBN had its -CN group pointing into the aqueous phase; while the 26DMHBN, similar to the PCP, had its -CN group pointing away from the aqueous phase. The tilt angles of the -CN group for both the 35DMHBN and 26DMHBN molecules at the air/water interface were around 25°-45° from the interface normal. These results provided insights on the understanding of the detailed balance of the competing factors, such as solvation of the polar head groups, hydrogen bonding and hydrophobic effects, etc., on influencing the absolute molecular orientation at the air/water interface.
文摘A non-relativistic microscopic mean field theory of finite nuclei is investigated where the nucleus is described as a collection of nucleons and delta resonances. The ground state properties of 90Zr nucleus have been investigated at equilibrium and large amplitude compression using a realistic effective baryon-baryon Hamiltonian based on Reid Soft Core (RSC) potential. The sensitivity of the ground state properties is studied, such as binding energy, nuclear radius, radial density distribution, and single particle energies to the degree of compression. It is found that the most of increasing in the nuclear energy generated under compression is used to create the massive Δ particles. For 90Zr nucleus under compression at 2.5 times density of the normal nuclear density, the excited nucleons to Δ 's are increased sharply up to 14% of the total number of constituents. This result is consistent with the values extracted from relativistic heavy-ion collisions. The single particle energy levels are calculated and their behaviors under compression are examined too. A good agreement between results with effective Hamiltonian and the phenomenologieal shell model for the low lying single-particle spectra is obtained. A considerable reduction in compressibility for the nucleus, and softening of the equation of state with the inclusion of the Δ's in the nuclear dynamics are suggested by the results.
文摘We consider the covalence characters of the 3d electron with the eg orbital freedoms and put forward a new mechanism of the orbital ordering (00) based on the direct coulomb repulsion in this article. The results show that the orbital-orbital interaction (OO-I) between the adjacent ions in 180-degree configuration is dominated by the superexchange energy accompanied by a weak orbital-spin coupling, and the OO-I in 90-degree configuration is monitored by the oxygen on-site coulomb repulsion. The ferro-OO is the stable ground state for the one-dimensional chain in the case of the 90-degree configuration.
基金Supported in part by the Foundation of Henan Educational Committee under Grant No.2009B140003
文摘In the context of topcolor-assisted technicolor (TC2) model, we study the charged and neutral top-pions production process γγ →W+ ∏t-∏t^0. We find that the production cross section is larger than that of the process γγ→ W+ H-H in the minimal supersymmetric standard model. With reasonable values of the parameters in the TC2 model, the cross section can reach the level of a few fb. Furthermore, the flavor-changing (FC) decay mode ∏t^0 → te^- is the best channel to detect the neutral top-pion due to the clean SM background. With a large number of events and the clean background, the neutral top-pion should be observable at future linear colliders operating in γγ mode at the TeV energy scale.
文摘The contribution of the resonant continuum to pairing correlations is investigated in the relativistic mean field theory plus Bardeen–Cooper–Schrieffer (BCS) approximation with a constant pairing strength. The resonance states with their widths in the continuum are considered explicitly. The numerical study is performed in an effective Lagrangian with the parameter set NLSH for neutron-rich nucleus <SUP>84</SUP>Ni. The results show that the effect of the proper treatment of the resonant continuum on pairing correlations for nucleus close to neutron drip line is important. It is found that the problem of an unphysical particle gas could be overcome when the pairing correlation is performed by using the resonant states instead of the discretized states in the continuum.
基金Supported by Hunan Province Science and Technology(2007FJ1012)the Scientific Research Fund of Hunan Provincial Education Department(09CY014)Doctoral Fund of HNUST
文摘In order to improve the thermal environment of high-temperature heading face,moisture content of supply air is reduced by dehumidification, and the relative humidity ofenvironment air of the heading face is also decreased.First, according to the coefficient ofperformance of dehumidifier, the capacity of dehumidification was calculated.Second, inthe engineering example of the heading face, quantitative changes of WBGT (Wet BulbGlobe Temperature) were compared between with dehumidification and without dehumidification.Based on WBGT standards, the thermal comfort of high-temperature environmentof heading face was evaluated between with dehumidification and without handling.Reducingthe relative humidity of airflow through dehumidification, the thermal comfort of ahigh-temperature environment of heading face can improve greatly.Even if dry bulb temperatureof airflow is not decreased, the thermal comfort of heading face environment isalso improved to some extent.
基金Supported by the National-Basic Research Program of China (2003CB615707) and the National Natural Science Foundation of China (20636020).
文摘The effects of sintering atmosphere on the properties of symmetric TiO2 membranes are studied with regard to sintering behavior, porosity, mean pore size, surface comPosition. and surface charge properties. The exerimental results show that the symmetric TiO2 membranes display better sintering activity in the air than in argon, and the mean pore diameters and porosities of the membrane sintered in argon are higher than those of the membrane sintered in the air at the same temperature. The surface compositions of the symmetric TiO2 membrane sintered in the air and in argon at different temperatures, as studied by X-ray photoelectron spectroscopy, are discussed in terms of their chemical composition, with particular emphasis on the valence state of the titanium ions. The correlation between the valence state of the titanium ions at the surface and the surface charge properties is examined.It is found that the presence of Ti^3+, introduced at the surface of the symmetric TiO2 membranes by sintering in a lower partial pressure of oxygen, is related to a significant decrease in the isoelectric point. TiO2 with Ti^4+ at the interface has an isoelectric point of 5.1, but the non-stoichiometric TiO2-x with Ti^3+ at the interface has a lower isoelectric point of 3.6.
基金Supported by the National Natural Science Foundation of China (20676015, 20806009), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (20070007055).
文摘Polyethersulfone(PES)film with regular microporous structure was formed using dichloromethane as the solvent via water vapor induced phase separation(VIPS).The effects of solution concentration,atmospheric humidity and temperature,as well as molecular weight of PES on the surface morphology of the polymer film were investigated.The surface morphology characterized by SEM showed that the pore size reduced as the solution concentration increased.There was an optimum range of relative humidity for the formation of regular pore structure, which was from 60%to 90%at concentration of 20 g·L-1 and 20°C.With the atmospheric temperature varied from 20 to 30°C,the pore became larger and the space between pores increased.The pore size in the PES film with low molecular weight was smaller than that with high molecular weight.
基金Supported by the National Natural Science Foundation of China(10135020)
文摘The geodesic acoustic mode (GAM), first predicted by Winsor, Johnson and Dawson in an attempt to explain some experimentally observed low frequency oscillations in stellarators, is a special electrostatic fluid mode with low mode number and coupled with the so-called geodesic curvature of a toroidally confined plasma. The recent on this mode are due to the close relevance of the stabi- lization of drift turbulence by both the zonal flow and the GAM. Previously, the GAM was illustrated in very simple geometries,
基金supported by the National Natural Science Foundation of China(Grant Nos.41531072,41404130,41504125&41674166)
文摘Previous theoretical studies have shown that dayside chorus can produce butterfly distribution of energetic electrons in the Earth's radiation belts by preferentially accelerating medium pitch angle electrons, but this requires the further confirmation from high- resolution satellite observation. Here, we report correlated Van Allen Probes data on wave and particle during the 1 I-13 April, 2014 geomagnetic storm. We find that a butterfly pitch angle distribution of relativistic electrons is formed around the location L = 4.52, corresponding to the presence of enhanced dayside chorus. Using a Gaussian distribution fit to the observed chorus spectra, we calculate the bounce-averaged diffusion rates and solve two-dimensional Fokker-Planck equation. Numerical results demonstrate that acceleration by dayside chorus can yield the electron flux evolution both in the energy and butterfly pitch angle distribution comparable to the observation, providing a further evidence for the formation of butterfly distribution of relativistic electrons driven by very low frequency (VLF) plasma waves.
基金supported by the National Natural Science Foundation of China(Grant Nos.11872313 and 12172297).
文摘In this study,we propose valley phononic crystals that consist of a hexagonal aluminum plate with six chiral arrangements of ligaments.Valley phononic crystals were introduced into a topological insulator(TI)system to produce topologically protected edge waves(TPEW s)along the topological interfaces.The implementation of chiral topological edge states is different from the implementation of topological edge states of systems with symmetry.Unlike the conventional breaking of mirror symmetry,a new complete band with topological edge modes gap was opened up at the Dirac point by tuning the difference in lengths of the ligaments in the chiral unit cells.We investigated the dispersion properties in chiral systems and applied the dispersion properties to waveguides on the interfaces to achieve designable route systems.Furthermore,we simulated the robust propagation of TPEWs in different routes and demonstrated their immunity to backscattering at defects.Finally,the existence of the valley Hall effect in chiral systems was demonstrated.The study findings may lead to the further study of the topological states of chiral materials.
基金the financial support by the National Natural Science Foundation of China (21771137)the Natural Science Foundation of Tianjin City (18JCJQJC47700)+1 种基金111 project (D17003)the Training Project of Innovation Team of Colleges and Universities in Tianjin (TD13-5020)
文摘In this work, we reported the synthesis of twodimensional spinel structure of ultrathin Co2AlO4 nanosheets via dealloying and subsequent annealing processes. Oxygen vacancy defects were further introduced into Co2AlO4 nanosheets by a mild solvothermal reduction method, resulting in large electrochemical surface area and high active site densities, making the related Co atoms get electrons, and producing more empty orbitals. The positive charge of Co and Al atoms adjacent to the O vacancies in VO-rich Co2AlO4 reduced significantly, that is, more electrons are concentrated on the Co and Al atoms. Those electrons closed to the Fermi level have a promoting effect during the H2O activation. As a result, the obtained ultrathin Co2AlO4 nanosheets with oxygen vacancies show a low overpotential of 280 m V at the current density of 10 mA cm^-2 and a small Tafel slope of70.98 m V dec^-1. Moreover, it also displays a remarkable stability in alkaline solution, which is superior to most of the reported Co3O4 electrocatalysts. The present work paves a new way to achieve efficient new energetic materials for sustainable community.