Self-trapping excitons(STEs) emission in metal halides has been a matter of interest, correlating with the strength of electron-phonon coupling in the lattice, which are usually caused by ions with ns~2 electronic str...Self-trapping excitons(STEs) emission in metal halides has been a matter of interest, correlating with the strength of electron-phonon coupling in the lattice, which are usually caused by ions with ns~2 electronic structure. In this work, Sb^(3+)/Te^(4+)ions doped Zn-based halide single crystals(SCs) with two STEs emissions have been synthesized and the possibility of its anti-counterfeiting application was explored.Further, the relationship between the strength of electron-phonon coupling and photoluminescence quantum yields(PLQYs) for STEs in a series of metal halides has been studied. And the semi-empirical range of the Huang-Rhys factors(S) for metal halides with excellent photoluminescence(PL) property has been summarized. This work provides ideas for further research into the relationship between luminescence performance and electron-phonon coupling of metal halides, and also provides a reference for designing the metal halides with high PLQYs.展开更多
The coupled nonlocal nonlinear Schrödinger equations with variable coefficients are researched using the nonstandard Hirota bilinear method.The two-soliton and double-hump one-soliton solutions for the equations ...The coupled nonlocal nonlinear Schrödinger equations with variable coefficients are researched using the nonstandard Hirota bilinear method.The two-soliton and double-hump one-soliton solutions for the equations are first obtained.By assigning different functions to the variable coefficients,we obtain V-shaped,Y-shaped,wave-type,exponential solitons,and so on.Next,we reveal the influence of the real and imaginary parts of the wave numbers on the double-hump structure based on the soliton solutions.Finally,by setting different wave numbers,we can change the distance and transmission direction of the solitons to analyze their dynamic behavior during collisions.This study establishes a theoretical framework for controlling the dynamics of optical fiber in nonlocal nonlinear systems.展开更多
It has been proved that there exists a cross coupling between vertical heat turbulent transport and vertical velocity by using linear thermodynamics. This result asserts that the vertical component of heat turbulent t...It has been proved that there exists a cross coupling between vertical heat turbulent transport and vertical velocity by using linear thermodynamics. This result asserts that the vertical component of heat turbulent transport flux is composed of both the transport of the vertical potential temperature gradient and the coupling transport of the vertical velocity. In this paper, the coupling effect of vertical velocity on vertical heat turbulent transportation is validated by using observed data from the atmospheric boundary layer to determine cross coupling coefficients, and a series of significant properties of turbulent transportation are opened out. These properties indicate that the cross coupling coefficient is a logarithm function of the dimensionless vertical velocity and dimensionless height, and is not only related to the friction velocity u., but also to the coupling roughness height zwo and the coupling temperature Two of the vertical velocity. In addition, the function relations suggest that only when the vertical velocity magnitude conforms to the limitation IW/u. I # 1, and is above the level zwo, then the vertical velocity leads to the cross coupling effect on the vertical heat turbulent transport flux. The cross coupling theory and experimental results provide a challenge to the traditional turbulent K closure theory and the Monin-Obukhov similarity theory.展开更多
This study investigates the impact of different water coupling coefficients on the blasting effect of red sandstone.The analysis is based on the theories of detonation wave and elastic wave,focusing on the variation i...This study investigates the impact of different water coupling coefficients on the blasting effect of red sandstone.The analysis is based on the theories of detonation wave and elastic wave,focusing on the variation in wall pressure of the blasting holes.Using DDNP explosive as the explosive load,blasting tests were conducted on red sandstone specimens with four different water coupling coefficients:1.20,1.33,1.50,and 2.00.The study examines the morphologies of the rock specimens after blasting under these different water coupling coefficients.Additionally,the fractal dimensions of the surface cracks resulting from the blasting were calculated to provide a quantitative evaluation of the extent of rock damage.CT scanning and 3D reconstruction were performed on the post-blasting specimens to visually depict the extent of damage and fractures within the rock.Additionally,the volume fractal dimension and damage degree of the post-blasting specimens are calculated.The findings are then combined with numerical simulation to facilitate auxiliary analysis.The results demonstrate that an increase in the water coupling coefficient leads to a reduction in the peak pressure on the hole wall and the crushing zone,enabling more of the explosion energy to be utilized for crack propagation following the explosion.The specimens exhibited distinct failure patterns,resulting in corresponding changes in fractal dimensions.The simulated pore wall pressure–time curve validated the derived theoretical results,whereas the stress cloud map and explosion energy-time curve demonstrated the buffering effect of the water medium.As the water coupling coefficient increases,the buffering effect of the water medium becomes increasingly prominent.展开更多
The reconstruction of emission coefficient is a key factor for the calculation of temperature field.However,most of the researches for determining arc plasmas are based on axisymmetric sources,little has been done to ...The reconstruction of emission coefficient is a key factor for the calculation of temperature field.However,most of the researches for determining arc plasmas are based on axisymmetric sources,little has been done to study non-axisymmetric arc plasmas.In order to reveal temperatures of a non-axisymmetric coupling arc,the distribution of emission coefficients must be reconstructed in advance.In this paper,the argon atomic line intensities of the coupling arc are obtained by using the imaging system that involves a high speed camera in conjunction with a neutral and a narrow-band filter.The converted programme between emission coefficients and emitted intensities is programmed based on MALDONADO＇s method.A displaced Gaussian model is used for evaluating the validity of the converted programme.Then,the emission coefficients of a free burning arc are reconstructed by MALDONADO＇s method and an Abel inversion,respectively,and good agreement is obtained.Finally,the emission coefficient profiles of the coupling arc are achieved.The results show that the distribution of emission coefficient for the coupling arc is non-axisymmetric.The emission coefficient profile is similar to an ellipse,and the short axis of the ellipse is in the direction that the two electrodes are arranged along.The peak temperature of the coupling arc is in the middle of both electrodes.There is a strong interaction between both arcs within the coupling arc.The proposed research solves difficulties for determining asymmetric arcs and enlarges the application scope of spectroscopic techniques.展开更多
We propose a method for estimating the mutual coupling coefficient among antennas in this paper which is based on the principle of signal subspace and the simulated annealing （SA） algorithm. The computer simulation ...We propose a method for estimating the mutual coupling coefficient among antennas in this paper which is based on the principle of signal subspace and the simulated annealing （SA） algorithm. The computer simulation has been conducted to illustrate the＇ excellent performance of this method and to demonstrate that it is statistically efficient. The benefit of this new method is that calibration signals and unknown signals can be received simultaneously, during the course of calibration.展开更多
According to a uniform and simple method of calculating spin-lattice coupling coefficients and the pert1rbation formulas of gi factors and hyperfine structure constants Ai based on the cluster approach for 3d7 ions in...According to a uniform and simple method of calculating spin-lattice coupling coefficients and the pert1rbation formulas of gi factors and hyperfine structure constants Ai based on the cluster approach for 3d7 ions in cubic,tetragonal and trigonal octahedral crystal fields, the spin-lattice coupling coefficients Fij (F11, Fl2, F44), Zij (Z11, Z12,Z44) and also g factor and hyperfine constant A for MgO:Co2+ are calculated by using the parameters obtained from the optical spectra without adjustable parameters. The calculated results show good agreement with the observed values.The difiiculty in explaining the coeficients Fij and Zij is therefore removed.展开更多
<div style="text-align:justify;"> Currently, coupled mode theory (CMT) is widely used for calculating the coupling coefficient of twin-core fibers (TCFs) that are used in a broad range of important app...<div style="text-align:justify;"> Currently, coupled mode theory (CMT) is widely used for calculating the coupling coefficient of twin-core fibers (TCFs) that are used in a broad range of important applications. This approach is highly accurate for scenarios with weak coupling between the cores but shows significant errors in the strong coupling scenarios, necessitating the use of a more accurate method for coupling coefficient calculations. Therefore, in this work, we calculate the coupling coefficients of TCFs using the supermode theory with finite element method (FEM) that has higher accuracy than CMT, particularly for the strong coupling TCF. To investigate the origin of the differences between the results obtained by these two methods, the modal field distributions of the supermodes of TCF are simulated and analyzed in detail. </div>展开更多
For the superstructure fiber grating （SFG） consisting of fiber Bragg grating （FBG） and long-period fiber grating （LPFG）, there exist three kinds of coupling： the contra-directional coupling between forward prop...For the superstructure fiber grating （SFG） consisting of fiber Bragg grating （FBG） and long-period fiber grating （LPFG）, there exist three kinds of coupling： the contra-directional coupling between forward propagating core mode and backward propagating core mode, the contra-directional coupling between core mode and cladding mode, and the co-directional coupling between core mode and cladding mode. By using the similarity transformation method for the coupled mode equations, the effects of three coupling coefficients κcoL, κclL, and κsL on the transmission and re- flection spectra of SFG have been investigated. The simulations show that the overall intensity of the transmission spectrum of SFG is decided by LPFG, that the main lobes of the transmission and reflectivity spectra of SFG are decided by coupling coefficients κcoL and κsL, and that the side lobes of the transmission and reflectivity spectra are decided by coupling coefficients κclL and κsL.展开更多
The response relationship between equivalent neutral wind speed anomaly(ENWSA)and sea-air temperature difference anomaly(SATDA)has been analyzed over four typical sea regions,i.e.,the Kuroshio Extension,the Gulf Strea...The response relationship between equivalent neutral wind speed anomaly(ENWSA)and sea-air temperature difference anomaly(SATDA)has been analyzed over four typical sea regions,i.e.,the Kuroshio Extension,the Gulf Stream,the Brazil-Malvinas Confluence and the Agulhas Return Current.The results show that ENWSA is more sensitive to SATDA than sea surface temperature anomaly(SSTA),which implies that SATDA seems to be a more suitable parameter than SSTA to analyze the mesoscale air-sea interactions.Here,the slope of the linear relation between ENWSA and SATDA is defined as the air-sea coupling coefficient.It is found that the values of the coupling coefficient over the four typical sea areas have obvious seasonal variations and geographical differences.In order to reveal the reason of the seasonal variation and geographical difference of the coupling coefficient,the influences of some environmental background factors,such as the spatially averaged sea surface temperature(SST),the spatially averaged air temperature,the spatially averaged sea-air temperature difference and the spatially averaged equivalent neutral wind speed,on the coupling coefficient are discussed in detail.The results reveal that the background sea-air temperature difference is an important environmental factor which directly affects the magnitude of the coupling coefficients,meanwhile,the seasonal and geographical variations of the coupling coefficient.展开更多
The first six Chebyshev polynomial coefficients (i.e., A00, A01, A10, A11, A02, A20) were derived from monthly mean geopotential height over East Asia for the period 1951-1983. Spectral analysis of these coefficients ...The first six Chebyshev polynomial coefficients (i.e., A00, A01, A10, A11, A02, A20) were derived from monthly mean geopotential height over East Asia for the period 1951-1983. Spectral analysis of these coefficients reveals relative maxima of power in the frequency bands of 200 months (- 16.7 years), 25 months (the quasi-biennial oscillation), 5-6 months, and 2-3 months. Cross-spectral characteristics between Chebyshev coefficients and the Southern Oscillation Index (SOI) were also explored. Coherence spectrum for the zonal and meridional circulation index (A01 and A 10) with the SOI was significant near 4 years, the QBO, and 2-3 months. Some physical explanations were offered for the spatial linkages (i.e., teleconnections) between the SO and atmospheric circulation anomalies overEast Asia.展开更多
By the two-scale homogenization approach we justify a two-scale model of ion transport through a layered membrane, with flows being driven by a pressure gradient and an external electrical field. By up-scaling, the el...By the two-scale homogenization approach we justify a two-scale model of ion transport through a layered membrane, with flows being driven by a pressure gradient and an external electrical field. By up-scaling, the electroosmotic flow equations in horizontal thin slits separated by thin solid layers are approximated by a homogenized system of macroscale equations in the form of the Poisson equation for induced vertical electrical field and Onsager's reciprocity relations between global fluxes (hydrodynamic and electric) and forces (horizontal pressure gradient and external electrical field). In addition, the two-scale approach provides macroscopic mobility coefficients in the Onsager relations. On this way, the cross-coupling kinetic coefficient is obtained in a form which does involves the ζ -potential among the data provided the surface current is negligible.展开更多
A quite general coupled variable coefficient modified KdV (VCmKdV) equation in a two-layer fluid systemis derived by means of the reductive perturbation method.Making use of the CK's direct method,some similarityr...A quite general coupled variable coefficient modified KdV (VCmKdV) equation in a two-layer fluid systemis derived by means of the reductive perturbation method.Making use of the CK's direct method,some similarityreductions of the coupled VCmKdV equation are obtained and their corresponding group explanations are discussed.Some exact solutions of the coupled equations are also presented.展开更多
Calculating the flow coefficient of a spool-valve is complicated due to the coupling–throttling effect in the throttling grooves of a proportional–directional valve.In this paper,a methodology for expressing the flo...Calculating the flow coefficient of a spool-valve is complicated due to the coupling–throttling effect in the throttling grooves of a proportional–directional valve.In this paper,a methodology for expressing the flow coefficient of coupled throttling grooves is proposed to resolve that difficulty.With this purpose,an approach of a 3 D numerical simulation and an experimental bench were introduced based on the prototype of a commercial proportional valve.The results show consistency between the numerical simulation and the bench test.Based on that,the concept of‘saturation limit’is introduced to describe the value gap between the current and saturated flows,so that the flow-coefficient saturation limit of the prototype in the process can be deducted.Accordingly,an approximate flow coefficient suitable for coupled throttling grooves within finite variable space,which is based on three typical throttling structures(i.e.O-shape,U-shape,and C-shape)of the coupled throttling grooves,is obtained based on an orthogonal test.The model results are consistent with the numerical and experimental results,with maximum errors of less than 5.29%and 5.34%,respectively.This suggests that the proposed method is effective in approximating the flow coefficient.展开更多
Using a transient thermoreflectance （TTR） technique, several Au films with different thicknesses on glass and SiC substrates are measured for thermal characterization of metMlic nano-films, including the electron ph...Using a transient thermoreflectance （TTR） technique, several Au films with different thicknesses on glass and SiC substrates are measured for thermal characterization of metMlic nano-films, including the electron phonon coupling factor G, interfazial thermal resistance R, and thermal conductivity Ks of the substrate. The rear heating-front detecting （RF） method is used to ensure the femtosecond temporal resolution. An intense laser beam is focused on the rear surface to heat the film, and another weak laser beam is focused on the very spot of the front surface to detect the change in the electron temperature. By varying the optical path delay between the two beams, a complete electron temperature profile can be scanned. Different from the normally used single-layer model, the double-layer model involving interfaciM thermal resistance is studied here. The electron temperature cooling profile can be affected by the electron energy transfer into the substrate or the electron-phonon interactions in the metallic films. For multiple-target optimization, the genetic algorithm （GA） is used to obtain both G and R. The experimental result gives a deep understanding of the mechanism of ultra-fast heat transfer in metals.展开更多
This study presents experimental evidence of the dependence of non-radiative recombination processes on the electron-phonon coupling of perovskite in perovskite solar cells(PSCs).Via A-site cation engineering,a weaker...This study presents experimental evidence of the dependence of non-radiative recombination processes on the electron-phonon coupling of perovskite in perovskite solar cells(PSCs).Via A-site cation engineering,a weaker electron-phonon coupling in perovskite has been achieved by introducing the structurally soft cyclohexane methylamine(CMA^(+))cation,which could serve as a damper to alleviate the mechanical stress caused by lattice oscillations,compared to the rigid phenethyl methylamine(PEA^(+))analog.It demonstrates a significantly lower non-radiative recombination rate,even though the two types of bulky cations have similar chemical passivation effects on perovskite,which might be explained by the suppressed carrier capture process and improved lattice geometry relaxation.The resulting PSCs achieve an exceptional power conversion efficiency(PCE)of 25.5%with a record-high opencircuit voltage(V_(OC))of 1.20 V for narrow bandgap perovskite(FAPbI_(3)).The established correlations between electron-phonon coupling and non-radiative decay provide design and screening criteria for more effective passivators for highly efficient PSCs approaching the Shockley-Queisser limit.展开更多
1 INTRODUCTIONKnowledge of the basic transport phenomena of ions in an ion exchange membrane isimportant for the application of such a membrane.Various studies on the developmentof mathematical models for predicting a...1 INTRODUCTIONKnowledge of the basic transport phenomena of ions in an ion exchange membrane isimportant for the application of such a membrane.Various studies on the developmentof mathematical models for predicting and correlating membrane transport rate havebeen published in recent years.More exact estimation of the diffusion coefficientshas been the subject of chief concern in many of these papers.For a bi-ionic systemwith the same valence,Sato et al.gave a method for estimating diffusion coefficients展开更多
By means of sn-function expansion method and cn-function expansion method, several kinds of explicit solutions to the coupled KdV equations with variable coefficients are obtained, which include three sets of periodic...By means of sn-function expansion method and cn-function expansion method, several kinds of explicit solutions to the coupled KdV equations with variable coefficients are obtained, which include three sets of periodic wave-like solutions. These solutions degenerate to solitary wave-like solutions at a certain limit. Some new solutions are presented.展开更多
This study investigated the interdiffusion of calcium ferrite/calcium titanate system in the time range of 0-120 min by the diffusion couple method in a CO/N2 reducing atmosphere at 700℃.The results show that after t...This study investigated the interdiffusion of calcium ferrite/calcium titanate system in the time range of 0-120 min by the diffusion couple method in a CO/N2 reducing atmosphere at 700℃.The results show that after the diffusion reaction occurred,no longitudinal agglomerations were present on the substrate surface on the calcium titanate side.When the diffusion time was increased to 105 min,a net vacancy flow from calcium titanate to calcium ferrite might have occurred,causing the surface of the calcium ferrite substrate to collapse.The thickness of the diffusion layer of the calcium ferrite/calcium titanate system was about 17-48μm,which conforms to the parabolic law of diffusion.The diffusion coefficient and the Ti^4+concentration in the calcium ferrite/calcium titanate system are related.This shows an increase in the diffusion coefficient with the increase of Ti^4+concentration,and the diffusion coefficient value was in the range of 10^−12-10^−11 cm^2·s^−1.展开更多
Studied in this paper is a(2+1)-dimensional coupled nonlinear Schr?dinger system with variable coefficients,which describes the propagation of an optical beam inside the two-dimensional graded-index waveguide amplifie...Studied in this paper is a(2+1)-dimensional coupled nonlinear Schr?dinger system with variable coefficients,which describes the propagation of an optical beam inside the two-dimensional graded-index waveguide amplifier with the polarization effects. According to the similarity transformation, we derive the type-Ⅰ and type-Ⅱ rogue-wave solutions. We graphically present two types of the rouge wave and discuss the influence of the diffraction parameter on the rogue waves.When the diffraction parameters are exponentially-growing-periodic, exponential, linear and quadratic parameters, we obtain the periodic rogue wave and composite rogue waves respectively.展开更多
基金supported by the financial aid from the National Natural Science Foundation of China (No. 22271273)International Partnership Program of Chinese Academy of Sciences (No. 121522KYSB20190022)。
文摘Self-trapping excitons(STEs) emission in metal halides has been a matter of interest, correlating with the strength of electron-phonon coupling in the lattice, which are usually caused by ions with ns~2 electronic structure. In this work, Sb^(3+)/Te^(4+)ions doped Zn-based halide single crystals(SCs) with two STEs emissions have been synthesized and the possibility of its anti-counterfeiting application was explored.Further, the relationship between the strength of electron-phonon coupling and photoluminescence quantum yields(PLQYs) for STEs in a series of metal halides has been studied. And the semi-empirical range of the Huang-Rhys factors(S) for metal halides with excellent photoluminescence(PL) property has been summarized. This work provides ideas for further research into the relationship between luminescence performance and electron-phonon coupling of metal halides, and also provides a reference for designing the metal halides with high PLQYs.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1604200)the National Natural Science Foundation of China(Grant No.12261131495)Institute of Systems Science,Beijing Wuzi University(Grant No.BWUISS21).
文摘The coupled nonlocal nonlinear Schrödinger equations with variable coefficients are researched using the nonstandard Hirota bilinear method.The two-soliton and double-hump one-soliton solutions for the equations are first obtained.By assigning different functions to the variable coefficients,we obtain V-shaped,Y-shaped,wave-type,exponential solitons,and so on.Next,we reveal the influence of the real and imaginary parts of the wave numbers on the double-hump structure based on the soliton solutions.Finally,by setting different wave numbers,we can change the distance and transmission direction of the solitons to analyze their dynamic behavior during collisions.This study establishes a theoretical framework for controlling the dynamics of optical fiber in nonlocal nonlinear systems.
基金This study has been supported by the National Natural Science Foundation of China under Grant No. 40633014.
文摘It has been proved that there exists a cross coupling between vertical heat turbulent transport and vertical velocity by using linear thermodynamics. This result asserts that the vertical component of heat turbulent transport flux is composed of both the transport of the vertical potential temperature gradient and the coupling transport of the vertical velocity. In this paper, the coupling effect of vertical velocity on vertical heat turbulent transportation is validated by using observed data from the atmospheric boundary layer to determine cross coupling coefficients, and a series of significant properties of turbulent transportation are opened out. These properties indicate that the cross coupling coefficient is a logarithm function of the dimensionless vertical velocity and dimensionless height, and is not only related to the friction velocity u., but also to the coupling roughness height zwo and the coupling temperature Two of the vertical velocity. In addition, the function relations suggest that only when the vertical velocity magnitude conforms to the limitation IW/u. I # 1, and is above the level zwo, then the vertical velocity leads to the cross coupling effect on the vertical heat turbulent transport flux. The cross coupling theory and experimental results provide a challenge to the traditional turbulent K closure theory and the Monin-Obukhov similarity theory.
基金National Key Research and Development Program of China(2021YFC2902103)National Natural Science Foundation of China(51934001)Fundamental Research Funds for the Central Universities(2023JCCXLJ02).
文摘This study investigates the impact of different water coupling coefficients on the blasting effect of red sandstone.The analysis is based on the theories of detonation wave and elastic wave,focusing on the variation in wall pressure of the blasting holes.Using DDNP explosive as the explosive load,blasting tests were conducted on red sandstone specimens with four different water coupling coefficients:1.20,1.33,1.50,and 2.00.The study examines the morphologies of the rock specimens after blasting under these different water coupling coefficients.Additionally,the fractal dimensions of the surface cracks resulting from the blasting were calculated to provide a quantitative evaluation of the extent of rock damage.CT scanning and 3D reconstruction were performed on the post-blasting specimens to visually depict the extent of damage and fractures within the rock.Additionally,the volume fractal dimension and damage degree of the post-blasting specimens are calculated.The findings are then combined with numerical simulation to facilitate auxiliary analysis.The results demonstrate that an increase in the water coupling coefficient leads to a reduction in the peak pressure on the hole wall and the crushing zone,enabling more of the explosion energy to be utilized for crack propagation following the explosion.The specimens exhibited distinct failure patterns,resulting in corresponding changes in fractal dimensions.The simulated pore wall pressure–time curve validated the derived theoretical results,whereas the stress cloud map and explosion energy-time curve demonstrated the buffering effect of the water medium.As the water coupling coefficient increases,the buffering effect of the water medium becomes increasingly prominent.
基金supported by National Natural Science Foundation of China (Grant Nos. 51175119,50775053)
文摘The reconstruction of emission coefficient is a key factor for the calculation of temperature field.However,most of the researches for determining arc plasmas are based on axisymmetric sources,little has been done to study non-axisymmetric arc plasmas.In order to reveal temperatures of a non-axisymmetric coupling arc,the distribution of emission coefficients must be reconstructed in advance.In this paper,the argon atomic line intensities of the coupling arc are obtained by using the imaging system that involves a high speed camera in conjunction with a neutral and a narrow-band filter.The converted programme between emission coefficients and emitted intensities is programmed based on MALDONADO＇s method.A displaced Gaussian model is used for evaluating the validity of the converted programme.Then,the emission coefficients of a free burning arc are reconstructed by MALDONADO＇s method and an Abel inversion,respectively,and good agreement is obtained.Finally,the emission coefficient profiles of the coupling arc are achieved.The results show that the distribution of emission coefficient for the coupling arc is non-axisymmetric.The emission coefficient profile is similar to an ellipse,and the short axis of the ellipse is in the direction that the two electrodes are arranged along.The peak temperature of the coupling arc is in the middle of both electrodes.There is a strong interaction between both arcs within the coupling arc.The proposed research solves difficulties for determining asymmetric arcs and enlarges the application scope of spectroscopic techniques.
基金Supported by the 863 High Technology Project ofChina (2001AA631050)
文摘We propose a method for estimating the mutual coupling coefficient among antennas in this paper which is based on the principle of signal subspace and the simulated annealing （SA） algorithm. The computer simulation has been conducted to illustrate the＇ excellent performance of this method and to demonstrate that it is statistically efficient. The benefit of this new method is that calibration signals and unknown signals can be received simultaneously, during the course of calibration.
文摘According to a uniform and simple method of calculating spin-lattice coupling coefficients and the pert1rbation formulas of gi factors and hyperfine structure constants Ai based on the cluster approach for 3d7 ions in cubic,tetragonal and trigonal octahedral crystal fields, the spin-lattice coupling coefficients Fij (F11, Fl2, F44), Zij (Z11, Z12,Z44) and also g factor and hyperfine constant A for MgO:Co2+ are calculated by using the parameters obtained from the optical spectra without adjustable parameters. The calculated results show good agreement with the observed values.The difiiculty in explaining the coeficients Fij and Zij is therefore removed.
文摘<div style="text-align:justify;"> Currently, coupled mode theory (CMT) is widely used for calculating the coupling coefficient of twin-core fibers (TCFs) that are used in a broad range of important applications. This approach is highly accurate for scenarios with weak coupling between the cores but shows significant errors in the strong coupling scenarios, necessitating the use of a more accurate method for coupling coefficient calculations. Therefore, in this work, we calculate the coupling coefficients of TCFs using the supermode theory with finite element method (FEM) that has higher accuracy than CMT, particularly for the strong coupling TCF. To investigate the origin of the differences between the results obtained by these two methods, the modal field distributions of the supermodes of TCF are simulated and analyzed in detail. </div>
基金Supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project, Ministry of Education of China (708064)Natural Science Foundation of Wuhan University of Technology (471-38650024)
文摘For the superstructure fiber grating （SFG） consisting of fiber Bragg grating （FBG） and long-period fiber grating （LPFG）, there exist three kinds of coupling： the contra-directional coupling between forward propagating core mode and backward propagating core mode, the contra-directional coupling between core mode and cladding mode, and the co-directional coupling between core mode and cladding mode. By using the similarity transformation method for the coupled mode equations, the effects of three coupling coefficients κcoL, κclL, and κsL on the transmission and re- flection spectra of SFG have been investigated. The simulations show that the overall intensity of the transmission spectrum of SFG is decided by LPFG, that the main lobes of the transmission and reflectivity spectra of SFG are decided by coupling coefficients κcoL and κsL, and that the side lobes of the transmission and reflectivity spectra are decided by coupling coefficients κclL and κsL.
基金The National Key Research and Development Program of China under contract No.2016YFC1401008the National Natural Science Foundation of China under contract Nos 41976167 and 41576170the National Natural Science Foundation of ChinaShandong Joint Fund for Marine Science Research Centers under contract No.U1606404.
文摘The response relationship between equivalent neutral wind speed anomaly(ENWSA)and sea-air temperature difference anomaly(SATDA)has been analyzed over four typical sea regions,i.e.,the Kuroshio Extension,the Gulf Stream,the Brazil-Malvinas Confluence and the Agulhas Return Current.The results show that ENWSA is more sensitive to SATDA than sea surface temperature anomaly(SSTA),which implies that SATDA seems to be a more suitable parameter than SSTA to analyze the mesoscale air-sea interactions.Here,the slope of the linear relation between ENWSA and SATDA is defined as the air-sea coupling coefficient.It is found that the values of the coupling coefficient over the four typical sea areas have obvious seasonal variations and geographical differences.In order to reveal the reason of the seasonal variation and geographical difference of the coupling coefficient,the influences of some environmental background factors,such as the spatially averaged sea surface temperature(SST),the spatially averaged air temperature,the spatially averaged sea-air temperature difference and the spatially averaged equivalent neutral wind speed,on the coupling coefficient are discussed in detail.The results reveal that the background sea-air temperature difference is an important environmental factor which directly affects the magnitude of the coupling coefficients,meanwhile,the seasonal and geographical variations of the coupling coefficient.
文摘The first six Chebyshev polynomial coefficients (i.e., A00, A01, A10, A11, A02, A20) were derived from monthly mean geopotential height over East Asia for the period 1951-1983. Spectral analysis of these coefficients reveals relative maxima of power in the frequency bands of 200 months (- 16.7 years), 25 months (the quasi-biennial oscillation), 5-6 months, and 2-3 months. Cross-spectral characteristics between Chebyshev coefficients and the Southern Oscillation Index (SOI) were also explored. Coherence spectrum for the zonal and meridional circulation index (A01 and A 10) with the SOI was significant near 4 years, the QBO, and 2-3 months. Some physical explanations were offered for the spatial linkages (i.e., teleconnections) between the SO and atmospheric circulation anomalies overEast Asia.
文摘By the two-scale homogenization approach we justify a two-scale model of ion transport through a layered membrane, with flows being driven by a pressure gradient and an external electrical field. By up-scaling, the electroosmotic flow equations in horizontal thin slits separated by thin solid layers are approximated by a homogenized system of macroscale equations in the form of the Poisson equation for induced vertical electrical field and Onsager's reciprocity relations between global fluxes (hydrodynamic and electric) and forces (horizontal pressure gradient and external electrical field). In addition, the two-scale approach provides macroscopic mobility coefficients in the Onsager relations. On this way, the cross-coupling kinetic coefficient is obtained in a form which does involves the ζ -potential among the data provided the surface current is negligible.
基金The project supported by National Natural Science Foundation of China under Grant Nos.10547124,10475055,and 90503006the Youth Foundation of Shanghai Jiao Tong University
文摘A quite general coupled variable coefficient modified KdV (VCmKdV) equation in a two-layer fluid systemis derived by means of the reductive perturbation method.Making use of the CK's direct method,some similarityreductions of the coupled VCmKdV equation are obtained and their corresponding group explanations are discussed.Some exact solutions of the coupled equations are also presented.
基金Project supported by the National Key R&D Program of China(No.2018YFC0810203)。
文摘Calculating the flow coefficient of a spool-valve is complicated due to the coupling–throttling effect in the throttling grooves of a proportional–directional valve.In this paper,a methodology for expressing the flow coefficient of coupled throttling grooves is proposed to resolve that difficulty.With this purpose,an approach of a 3 D numerical simulation and an experimental bench were introduced based on the prototype of a commercial proportional valve.The results show consistency between the numerical simulation and the bench test.Based on that,the concept of‘saturation limit’is introduced to describe the value gap between the current and saturated flows,so that the flow-coefficient saturation limit of the prototype in the process can be deducted.Accordingly,an approximate flow coefficient suitable for coupled throttling grooves within finite variable space,which is based on three typical throttling structures(i.e.O-shape,U-shape,and C-shape)of the coupled throttling grooves,is obtained based on an orthogonal test.The model results are consistent with the numerical and experimental results,with maximum errors of less than 5.29%and 5.34%,respectively.This suggests that the proposed method is effective in approximating the flow coefficient.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50730006,50976053,and 50906042)
文摘Using a transient thermoreflectance （TTR） technique, several Au films with different thicknesses on glass and SiC substrates are measured for thermal characterization of metMlic nano-films, including the electron phonon coupling factor G, interfazial thermal resistance R, and thermal conductivity Ks of the substrate. The rear heating-front detecting （RF） method is used to ensure the femtosecond temporal resolution. An intense laser beam is focused on the rear surface to heat the film, and another weak laser beam is focused on the very spot of the front surface to detect the change in the electron temperature. By varying the optical path delay between the two beams, a complete electron temperature profile can be scanned. Different from the normally used single-layer model, the double-layer model involving interfaciM thermal resistance is studied here. The electron temperature cooling profile can be affected by the electron energy transfer into the substrate or the electron-phonon interactions in the metallic films. For multiple-target optimization, the genetic algorithm （GA） is used to obtain both G and R. The experimental result gives a deep understanding of the mechanism of ultra-fast heat transfer in metals.
基金supported by the National Natural Science Foundation of China(U21A20331,81903743,22005322,22279151,and 22275004)National Science Fund for Distinguished Young Scholars(21925506).
文摘This study presents experimental evidence of the dependence of non-radiative recombination processes on the electron-phonon coupling of perovskite in perovskite solar cells(PSCs).Via A-site cation engineering,a weaker electron-phonon coupling in perovskite has been achieved by introducing the structurally soft cyclohexane methylamine(CMA^(+))cation,which could serve as a damper to alleviate the mechanical stress caused by lattice oscillations,compared to the rigid phenethyl methylamine(PEA^(+))analog.It demonstrates a significantly lower non-radiative recombination rate,even though the two types of bulky cations have similar chemical passivation effects on perovskite,which might be explained by the suppressed carrier capture process and improved lattice geometry relaxation.The resulting PSCs achieve an exceptional power conversion efficiency(PCE)of 25.5%with a record-high opencircuit voltage(V_(OC))of 1.20 V for narrow bandgap perovskite(FAPbI_(3)).The established correlations between electron-phonon coupling and non-radiative decay provide design and screening criteria for more effective passivators for highly efficient PSCs approaching the Shockley-Queisser limit.
基金Supported by the Post-doctoral Foundation of China
文摘1 INTRODUCTIONKnowledge of the basic transport phenomena of ions in an ion exchange membrane isimportant for the application of such a membrane.Various studies on the developmentof mathematical models for predicting and correlating membrane transport rate havebeen published in recent years.More exact estimation of the diffusion coefficientshas been the subject of chief concern in many of these papers.For a bi-ionic systemwith the same valence,Sato et al.gave a method for estimating diffusion coefficients
文摘By means of sn-function expansion method and cn-function expansion method, several kinds of explicit solutions to the coupled KdV equations with variable coefficients are obtained, which include three sets of periodic wave-like solutions. These solutions degenerate to solitary wave-like solutions at a certain limit. Some new solutions are presented.
基金This work was financially supported by the National Natural Science Foundation of China(No.51674084).
文摘This study investigated the interdiffusion of calcium ferrite/calcium titanate system in the time range of 0-120 min by the diffusion couple method in a CO/N2 reducing atmosphere at 700℃.The results show that after the diffusion reaction occurred,no longitudinal agglomerations were present on the substrate surface on the calcium titanate side.When the diffusion time was increased to 105 min,a net vacancy flow from calcium titanate to calcium ferrite might have occurred,causing the surface of the calcium ferrite substrate to collapse.The thickness of the diffusion layer of the calcium ferrite/calcium titanate system was about 17-48μm,which conforms to the parabolic law of diffusion.The diffusion coefficient and the Ti^4+concentration in the calcium ferrite/calcium titanate system are related.This shows an increase in the diffusion coefficient with the increase of Ti^4+concentration,and the diffusion coefficient value was in the range of 10^−12-10^−11 cm^2·s^−1.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11772017,11272023,and 11471050the Fund of State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications),China(IPOC:2017ZZ05)the Fundamental Research Funds for the Central Universities of China under Grant No.2011BUPTYB02
文摘Studied in this paper is a(2+1)-dimensional coupled nonlinear Schr?dinger system with variable coefficients,which describes the propagation of an optical beam inside the two-dimensional graded-index waveguide amplifier with the polarization effects. According to the similarity transformation, we derive the type-Ⅰ and type-Ⅱ rogue-wave solutions. We graphically present two types of the rouge wave and discuss the influence of the diffraction parameter on the rogue waves.When the diffraction parameters are exponentially-growing-periodic, exponential, linear and quadratic parameters, we obtain the periodic rogue wave and composite rogue waves respectively.
