The ground roll and body wave usually show significant differences in arrival time, frequency content, and polarization characteristics, and conventional polarization filters that operate in either the time or frequen...The ground roll and body wave usually show significant differences in arrival time, frequency content, and polarization characteristics, and conventional polarization filters that operate in either the time or frequency domain cannot consider all these elements. Therefore, we have developed a time-frequency dependent polarization filter based on the S transform to attenuate the ground roll in seismic records. Our approach adopts the complex coefficients of the S transform of the multi-component seismic data to estimate the local polarization attributes and utilizes the estimated attributes to construct the filter function. In this study, we select the S transform to design this polarization filter because its scalable window length can ensure the same number of cycles of a Fourier sinusoid, thereby rendering more precise estimation of local polarization attributes. The results of applying our approach in synthetic and real data examples demonstrate that the proposed polarization filter can effectively attenuate the ground roll and successfully preserve the body wave.展开更多
In this paper, we calculate the low-lying spectra of a single-electron magnetic quantum ring with an offcenter Coulomb impurity, where the magnetic field is zero within the ring and constant elsewhere. The impurity, e...In this paper, we calculate the low-lying spectra of a single-electron magnetic quantum ring with an offcenter Coulomb impurity, where the magnetic field is zero within the ring and constant elsewhere. The impurity, either an acceptor or a donor, is located at a distance d as measured from the plane of the ring along the vertical z direction. The magnetic moments are found in order to get visible discontinuities at the points of the ground-state orbital angular momentum L transitions induced by magnetic fields.展开更多
A base function expressed with Chebyshev polynomials is reached. The relationship between the coefficients of the partial differential equation and the base function is deduced. Using the relationship, one can obtain ...A base function expressed with Chebyshev polynomials is reached. The relationship between the coefficients of the partial differential equation and the base function is deduced. Using the relationship, one can obtain nearly the same results as those calculated by Fast Fourier Transformation (FFT). The pseudo-spectral matrix method is applied in this paper to simulate numerically the incompressible laminar boundary flow on a plate. The simulation proves to be precise and efficient.展开更多
We performed high-level ab initio calculations on electronic structure of Na K. The potential energy curves (PECs) of 10 Λ-S states correlated with the three lowest dissociation limits have been calculated. On the ba...We performed high-level ab initio calculations on electronic structure of Na K. The potential energy curves (PECs) of 10 Λ-S states correlated with the three lowest dissociation limits have been calculated. On the basis of the calculated PECs, the spectroscopic constants of the boundΛ-S states are obtained, which are in good agreement with experimental results. The maximum vibrational quantum numbers of the singlet ground state X^1Σ^+ and the triplet ground state a^3Σ^+ have been analyzed with the semiclassical scattering theory. Transition properties including transition dipole moments, Franck-Condon factors, and radiative lifetimes have been investigated. The research results indicate that such calculations can provide fairly reliable estimation of parameters for the ultracold alkali diatomic molecular experiment.展开更多
To expose the statistical properties of the degenerated spectrum, with the aid of the random matrix theory, a possible form of the NNS distribution function of the degenerate spectrum was proposed by providing a solut...To expose the statistical properties of the degenerated spectrum, with the aid of the random matrix theory, a possible form of the NNS distribution function of the degenerate spectrum was proposed by providing a solution in terms of the same-degeneracy case. The results indicate that the target spectrum is transformed into two sub-spectra： a random one and a regular one, and that the repulsion level of the regular spectrum is also decreased.展开更多
In random vibration analysis, the importance of spectral moments of the response stems from their relevance to system performance prediction. Usually,spectral moments are obtained by the frequency domain method. In pr...In random vibration analysis, the importance of spectral moments of the response stems from their relevance to system performance prediction. Usually,spectral moments are obtained by the frequency domain method. In present paper, the random response spectral moments of elastic-viscoelastic combined systems are calculated by complex modal analysis in the time domain. The analytical form results are obtained for random response spectral moments of an elastic-viscoelastic combined system to a stationary white noise excitation. The method presented is simple and easy to apply. It is hoped that this study would pave a way for the analysis of reliability of elastic-viscoelastic combined systems subjected to random excitations.展开更多
In this paper, a negatively charged exciton trapped by a spherical parabolic quantum dot has been investigated. The energy spectra of low-lying states are calculated by means of matrix diagonalization. The important f...In this paper, a negatively charged exciton trapped by a spherical parabolic quantum dot has been investigated. The energy spectra of low-lying states are calculated by means of matrix diagonalization. The important feature of the low-lying states of the negatively charged excitons in a spherical quantum dot is obtained via an analysis of the energy spectra.展开更多
A new structure containing negative refractive index dielectric layer（NRlDL） is introduced into microcavity. The properties of the new mierocavity organic light-emitting devices（MOLEDs） are investigated. In the ex...A new structure containing negative refractive index dielectric layer（NRlDL） is introduced into microcavity. The properties of the new mierocavity organic light-emitting devices（MOLEDs） are investigated. In the experiment, the transfer matrix method is adopted. The dependence of reflectance and transmittance on the refractive index and thickness of NRIDL are analyzed in detail. Compared with the electroluminescence spectra of non-NRIDL diodes, the line widths of the spectra of the MOLEDs are narrower and all the peaks enhance. The results show that the new structure is beneficial to improve the performance and reduce the thickness of microcavity devices.展开更多
We theoretically investigate the optical absorption spectra and charge density by subjecting a GaAs quantum well to both an intense terahertz (THz)-frequency driving field and an optical pulse within the theory of den...We theoretically investigate the optical absorption spectra and charge density by subjecting a GaAs quantum well to both an intense terahertz (THz)-frequency driving field and an optical pulse within the theory of density matrix. In presence of a strong THz field, the optical transitions in quantum well subbands are altered by the THz field. The alteration has a direct impact on the optical absorption and the charge density. The excitonic peak splitting and THz optical sideband in the absorption spectra show up when changing the THz field intensity and/or frequency. The Autler-Towns splitting is a result from the THz nonlinear dynamics of confined excitons. On the other hand, the carrier charge density is created as wave packets formed by coherent superposition of several eigenstates. The charge density exhibitsquantum beats for short pulses and/or wider wells and is modulated by the THz field.展开更多
The electric characteristics of Ge quantum dot grown by molecular beam epitaxy in Si matrix were investigated by admittance spectroscopy and deep level transient spectroscopy. The admittance spectroscopy measurements ...The electric characteristics of Ge quantum dot grown by molecular beam epitaxy in Si matrix were investigated by admittance spectroscopy and deep level transient spectroscopy. The admittance spectroscopy measurements show that the activation energy of 0.341eV can be considered as the emitting energy of hole from the ground state of the quantum dot. And the capacitance variation with temperature of the sample shows a platform at various frequencies with reverse bias (0.5 V,) which indicates that the boundary of space charge region is located at the quantum dot layer where the large confined hole concentration blocks the further extension of space charge region. When the temperature increases from 120K to 200K, the holes in the dot emit out completely. The position of the platform shifting with the increase of the applied frequency shows the frequency effects of the charges in the quantum dot. The deep level transient spectroscopy results show that the charge concentration in the Ge quantum dot is a function of the pulse duration and the reverse bias voltage, the activation energy and capture cross-section of hole decrease with the increase of pulse duration due to the Coulomb charging effect. The valence-band offsets of hole in Ge dot obtained by admittance spectroscopy and deep level transient spectroscopy are 0.341 and 0.338eV, respectively.展开更多
There is little low-and-high frequency information on seismic data in seismic exploration,resulting in narrower bandwidth and lower seismic resolution.It considerably restricts the prediction accuracy of thin reservoi...There is little low-and-high frequency information on seismic data in seismic exploration,resulting in narrower bandwidth and lower seismic resolution.It considerably restricts the prediction accuracy of thin reservoirs and thin interbeds.This study proposes a novel method to constrain improving seismic resolution in the time and frequency domain.The expected wavelet spectrum is used in the frequency domain to broaden the seismic spectrum range and increase the octave.In the time domain,the Frobenius vector regularization of the Hessian matrix is used to constrain the horizontal continuity of the seismic data.It eff ectively protects the signal-to-noise ratio of seismic data while the longitudinal seismic resolution is improved.This method is applied to actual post-stack seismic data and pre-stack gathers dividedly.Without abolishing the phase characteristics of the original seismic data,the time resolution is signifi cantly improved,and the structural features are clearer.Compared with the traditional spectral simulation and deconvolution methods,the frequency distribution is more reasonable,and seismic data has higher resolution.展开更多
基金supported by the National Science and Technology Major Project of China(Grant No.2011ZX05014 and 2011ZX05008-005)
文摘The ground roll and body wave usually show significant differences in arrival time, frequency content, and polarization characteristics, and conventional polarization filters that operate in either the time or frequency domain cannot consider all these elements. Therefore, we have developed a time-frequency dependent polarization filter based on the S transform to attenuate the ground roll in seismic records. Our approach adopts the complex coefficients of the S transform of the multi-component seismic data to estimate the local polarization attributes and utilizes the estimated attributes to construct the filter function. In this study, we select the S transform to design this polarization filter because its scalable window length can ensure the same number of cycles of a Fourier sinusoid, thereby rendering more precise estimation of local polarization attributes. The results of applying our approach in synthetic and real data examples demonstrate that the proposed polarization filter can effectively attenuate the ground roll and successfully preserve the body wave.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 50371058 and 90103028
文摘In this paper, we calculate the low-lying spectra of a single-electron magnetic quantum ring with an offcenter Coulomb impurity, where the magnetic field is zero within the ring and constant elsewhere. The impurity, either an acceptor or a donor, is located at a distance d as measured from the plane of the ring along the vertical z direction. The magnetic moments are found in order to get visible discontinuities at the points of the ground-state orbital angular momentum L transitions induced by magnetic fields.
文摘A base function expressed with Chebyshev polynomials is reached. The relationship between the coefficients of the partial differential equation and the base function is deduced. Using the relationship, one can obtain nearly the same results as those calculated by Fast Fourier Transformation (FFT). The pseudo-spectral matrix method is applied in this paper to simulate numerically the incompressible laminar boundary flow on a plate. The simulation proves to be precise and efficient.
基金supported by the National Key Research and Development Program of China(No.2017YFA0304900,No.2017YFA0402300,and No.2016YFA0300600)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB28000000 and No.XDB07030000)+2 种基金the National Natural Science Foundation of China(No.11604334,No.11575099 and No.11474347)the Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics(No.KF201807)the Science Challenge Project(No.TZ2016005)
文摘We performed high-level ab initio calculations on electronic structure of Na K. The potential energy curves (PECs) of 10 Λ-S states correlated with the three lowest dissociation limits have been calculated. On the basis of the calculated PECs, the spectroscopic constants of the boundΛ-S states are obtained, which are in good agreement with experimental results. The maximum vibrational quantum numbers of the singlet ground state X^1Σ^+ and the triplet ground state a^3Σ^+ have been analyzed with the semiclassical scattering theory. Transition properties including transition dipole moments, Franck-Condon factors, and radiative lifetimes have been investigated. The research results indicate that such calculations can provide fairly reliable estimation of parameters for the ultracold alkali diatomic molecular experiment.
基金V. ACKN0WLEDGMENT This work was supported by the National Natural Sci- ence Foundation of China （No.10375024） and the Science Foundation of Hunan Educational Committee.
文摘To expose the statistical properties of the degenerated spectrum, with the aid of the random matrix theory, a possible form of the NNS distribution function of the degenerate spectrum was proposed by providing a solution in terms of the same-degeneracy case. The results indicate that the target spectrum is transformed into two sub-spectra： a random one and a regular one, and that the repulsion level of the regular spectrum is also decreased.
文摘In random vibration analysis, the importance of spectral moments of the response stems from their relevance to system performance prediction. Usually,spectral moments are obtained by the frequency domain method. In present paper, the random response spectral moments of elastic-viscoelastic combined systems are calculated by complex modal analysis in the time domain. The analytical form results are obtained for random response spectral moments of an elastic-viscoelastic combined system to a stationary white noise excitation. The method presented is simple and easy to apply. It is hoped that this study would pave a way for the analysis of reliability of elastic-viscoelastic combined systems subjected to random excitations.
基金The project supported by National Natural Science Foundation of China under Grant No. 10475021 and the Natured Science Foundation of Guangdong Province of China under Grant No. 04009519
文摘In this paper, a negatively charged exciton trapped by a spherical parabolic quantum dot has been investigated. The energy spectra of low-lying states are calculated by means of matrix diagonalization. The important feature of the low-lying states of the negatively charged excitons in a spherical quantum dot is obtained via an analysis of the energy spectra.
基金Natural Science Research Item of Education Department of Henan Province(2008A430009)Doctor Foundation of Henan Polytechnic University(B2008-22)
文摘A new structure containing negative refractive index dielectric layer（NRlDL） is introduced into microcavity. The properties of the new mierocavity organic light-emitting devices（MOLEDs） are investigated. In the experiment, the transfer matrix method is adopted. The dependence of reflectance and transmittance on the refractive index and thickness of NRIDL are analyzed in detail. Compared with the electroluminescence spectra of non-NRIDL diodes, the line widths of the spectra of the MOLEDs are narrower and all the peaks enhance. The results show that the new structure is beneficial to improve the performance and reduce the thickness of microcavity devices.
基金the National Fund for Distinguished Young Scholars of China under，国家自然科学基金，国家重点基础研究发展计划(973计划)，上海市科委资助项目
文摘We theoretically investigate the optical absorption spectra and charge density by subjecting a GaAs quantum well to both an intense terahertz (THz)-frequency driving field and an optical pulse within the theory of density matrix. In presence of a strong THz field, the optical transitions in quantum well subbands are altered by the THz field. The alteration has a direct impact on the optical absorption and the charge density. The excitonic peak splitting and THz optical sideband in the absorption spectra show up when changing the THz field intensity and/or frequency. The Autler-Towns splitting is a result from the THz nonlinear dynamics of confined excitons. On the other hand, the carrier charge density is created as wave packets formed by coherent superposition of several eigenstates. The charge density exhibitsquantum beats for short pulses and/or wider wells and is modulated by the THz field.
基金Project(60276025) supported by the National Natural Science Foundation of China
文摘The electric characteristics of Ge quantum dot grown by molecular beam epitaxy in Si matrix were investigated by admittance spectroscopy and deep level transient spectroscopy. The admittance spectroscopy measurements show that the activation energy of 0.341eV can be considered as the emitting energy of hole from the ground state of the quantum dot. And the capacitance variation with temperature of the sample shows a platform at various frequencies with reverse bias (0.5 V,) which indicates that the boundary of space charge region is located at the quantum dot layer where the large confined hole concentration blocks the further extension of space charge region. When the temperature increases from 120K to 200K, the holes in the dot emit out completely. The position of the platform shifting with the increase of the applied frequency shows the frequency effects of the charges in the quantum dot. The deep level transient spectroscopy results show that the charge concentration in the Ge quantum dot is a function of the pulse duration and the reverse bias voltage, the activation energy and capture cross-section of hole decrease with the increase of pulse duration due to the Coulomb charging effect. The valence-band offsets of hole in Ge dot obtained by admittance spectroscopy and deep level transient spectroscopy are 0.341 and 0.338eV, respectively.
基金supported by the PetroChina Prospective,Basic,and Strategic Technology Research Project(No.2021DJ0606).
文摘There is little low-and-high frequency information on seismic data in seismic exploration,resulting in narrower bandwidth and lower seismic resolution.It considerably restricts the prediction accuracy of thin reservoirs and thin interbeds.This study proposes a novel method to constrain improving seismic resolution in the time and frequency domain.The expected wavelet spectrum is used in the frequency domain to broaden the seismic spectrum range and increase the octave.In the time domain,the Frobenius vector regularization of the Hessian matrix is used to constrain the horizontal continuity of the seismic data.It eff ectively protects the signal-to-noise ratio of seismic data while the longitudinal seismic resolution is improved.This method is applied to actual post-stack seismic data and pre-stack gathers dividedly.Without abolishing the phase characteristics of the original seismic data,the time resolution is signifi cantly improved,and the structural features are clearer.Compared with the traditional spectral simulation and deconvolution methods,the frequency distribution is more reasonable,and seismic data has higher resolution.
