The phase difference method (PDM) is presented for the direction of arrival (DOA) estimation of the narrowband source. It estimates the DOA by measuring the reciprocal of the phase range of the sensor output spectra a...The phase difference method (PDM) is presented for the direction of arrival (DOA) estimation of the narrowband source. It estimates the DOA by measuring the reciprocal of the phase range of the sensor output spectra at the interest frequency bin. The peak width and variance of the PDM are presented. The PDM can distinguish closely spaced sources with different and unknown center frequencies as long as they are separated with at least one frequency bin. The simulation results show that the PDM has a better resolution than that of the conventional beamforming.展开更多
The dynamical-wave routing model of the urban unsteady and non-pressure rain pipe flow was established by conservation of mass, momentum and energy, and it was solved by applying the four point implicit difference met...The dynamical-wave routing model of the urban unsteady and non-pressure rain pipe flow was established by conservation of mass, momentum and energy, and it was solved by applying the four point implicit difference method and the pursuit method. It was obtained from the experiment checking and comparative analysis that the dynamical-wave muting model can reflect influence like attenuate and backwater when flood peak propagate in pipeline with high calculation precision and vast application scope, and it can be applied in routing of urban rain pipe flow of different slopes and inflow conditions. The routing model supplies a scientific foundation for the town rainfall piping design or checking, disaster administration of storm runoff, and so on.展开更多
The exact short time propagator, in a form similar to the Crank-Nicholson method but in the spirit of spectrally transformed Hamiltonian, was proposed to solve the triatomic reactive time-dependent schrodinger equatio...The exact short time propagator, in a form similar to the Crank-Nicholson method but in the spirit of spectrally transformed Hamiltonian, was proposed to solve the triatomic reactive time-dependent schrodinger equation. This new propagator is exact and unconditionally convergent for calculating reactive scattering processes with large time step sizes. In order to improve the computational efficiency, the spectral difference method was applied. This resulted the Hamiltonian with elements confined in a narrow diagonal band. In contrast to our previous theoretical work, the discrete variable representation was applied and resulted in full Hamiltonian matrix. As examples, the collision energy-dependent probability of the triatomic H＋H2 and O＋O2 reaction are calculated. The numerical results demonstrate that this new propagator is numerically accurate and capable of propagating the wave packet with large time steps. However, the efficiency and accuracy of this new propagator strongly depend on the mathematical method for solving the involved linear equations and the choice of preconditioner.展开更多
An algorithm （differential mode） is presented for the improvement of harmonic tidal analysis along T/P tracks, in which the differences between the observed sea surface heights at adjacent points are taken as observ...An algorithm （differential mode） is presented for the improvement of harmonic tidal analysis along T/P tracks, in which the differences between the observed sea surface heights at adjacent points are taken as observations. Also, the observation equations are constrained with the results of the crossover analysis; the parameter estimations are performed at 0.1° latitude intervals by the least squares. Cycle 10 to 330 T/P altimeter data covering the China Sea and the Northwest Pacific Ocean （2°-50° N,105°-150° E） are adopted for a refined along-track harmonic tidal analysis, and harmonic constants of 12 constituents in 8 474 points are obtained, which indicates that the algorithm can efficiently remove non-tidal effects in the altimeter observations, and improve the precision of tide parameters. Moreover, parameters along altimetry tracks represent a smoother distribution than those obtained by traditional algorithms. The root mean squares of the fitting errors between the tidal height model and the observations reduce from 11 cm to 1.3 cm.展开更多
The Effects of pressure stress work and viscous dissipation in mixed convection flow along a vertical fiat plate have been investigated. The results are obtained by transforming the governing system of boundary layer ...The Effects of pressure stress work and viscous dissipation in mixed convection flow along a vertical fiat plate have been investigated. The results are obtained by transforming the governing system of boundary layer equations into a system of non-dimensional equations and by applying implicit finite difference method together with Newton＇s linearization approximation. Numerical results for different values of pressure stress work parameter, viscous dissipation parameter and Prandtl number have been obtained. The velocity profiles, temperature distributions, skin friction co-efficient and the rate of heat transfer have been presented graphically for the effects of the aforementioned parameters.展开更多
With the increasing researches on geotechnical properties of the diesel contaminated soil( DCS),the water content measured is indispensable part during the early period. In this study,the relative error of water conte...With the increasing researches on geotechnical properties of the diesel contaminated soil( DCS),the water content measured is indispensable part during the early period. In this study,the relative error of water content measurement using the traditional method is as high as 20. 78%,which is no longer suitable for contaminated soil. Through a series of tests to measure the loss coefficient of diesel in the drying time,the authors finally proposed a modified calculation formula for test samples. The results show that the maximum relative error calculated by using the modified formula is 0. 96%,far lower than that of traditional formula,which can provide accurate data for further study of diesel contaminated soil.展开更多
A numerical study has been carried out to investigate the effect of aspect ratio on heat transfer by natural convection of nanofluid taking Cu nano particles and the water as based fluid. The flow is laminar, steady s...A numerical study has been carried out to investigate the effect of aspect ratio on heat transfer by natural convection of nanofluid taking Cu nano particles and the water as based fluid. The flow is laminar, steady state, axisymmetric two-dimensional in a vertical cylindrical channel filled with porous media. Heat is generated uniformly along the center of the channel with its vertical surface remain with cooled constant wall temperature and insulated horizontal top and bottom surfaces. The governing equations which used are continuity, momentum and energy equations using Darcy law and Boussinesq＇s approximation which are transformed to dimensionless equations. The finite difference approach is used to obtain all the computational results using the MATLAB-7 program. The parameters affected on the system are Rayleigh number ranging within （10≤ Ra ≤ 103）, aspect ratio （1 ≤ As 〈 5） and the volume fraction （0 ≤0 〈 0.2）. The results obtained are presented graphically in the form of streamline and isotherm contour plots and the results show that as ~ increase from 0.01 to 0.2 the value of the mean Nusselt number increase 50.4% for Ra = 1,000.展开更多
This article is devoted to the study of high order accuracy difference methods tor the Cahn-rnmara equation. A three level linearized compact difference scheme is derived. The u^ique solvability and uaconditional conv...This article is devoted to the study of high order accuracy difference methods tor the Cahn-rnmara equation. A three level linearized compact difference scheme is derived. The u^ique solvability and uaconditional convergence of the difference solution are proved. The convergence order is O（T2＋h4） in the maximum norm. The mass conservation and the non-increase of the total energy are also verified. Some numerical examples are given to demonstrate the theoretical results.展开更多
A high-speed digital camera is used to record the saltation of three sand samples(diameter range:300–500,200–300 and100–125μm).This is followed by an overlapping particle tracking algorithm to reconstruct the salt...A high-speed digital camera is used to record the saltation of three sand samples(diameter range:300–500,200–300 and100–125μm).This is followed by an overlapping particle tracking algorithm to reconstruct the saltating trajectory and the differential scheme to abstract the kinetic parameters of saltating grains.The velocity results confirm the propagating feature of saltation in maintaining near-face aeolian sand transport.Moreover,the acceleration of saltating sand grains was obtained directly from the reconstructed trajectory,and the results reveal that the climbing stage of the saltating trajectory represents an critical process of energy transfer while the sand grains travel through air.展开更多
基金the National Science Foundation under Grant No. 60672136the the Doctorate Foundation of Northwestern Polytechnical University under Grant No.CX200803
文摘The phase difference method (PDM) is presented for the direction of arrival (DOA) estimation of the narrowband source. It estimates the DOA by measuring the reciprocal of the phase range of the sensor output spectra at the interest frequency bin. The peak width and variance of the PDM are presented. The PDM can distinguish closely spaced sources with different and unknown center frequencies as long as they are separated with at least one frequency bin. The simulation results show that the PDM has a better resolution than that of the conventional beamforming.
基金Hunan Provincial Education Department of Key Projects(No.08A019)Funded Projects in Hunan Science and Technology Department(No.2008SK4029)
文摘The dynamical-wave routing model of the urban unsteady and non-pressure rain pipe flow was established by conservation of mass, momentum and energy, and it was solved by applying the four point implicit difference method and the pursuit method. It was obtained from the experiment checking and comparative analysis that the dynamical-wave muting model can reflect influence like attenuate and backwater when flood peak propagate in pipeline with high calculation precision and vast application scope, and it can be applied in routing of urban rain pipe flow of different slopes and inflow conditions. The routing model supplies a scientific foundation for the town rainfall piping design or checking, disaster administration of storm runoff, and so on.
文摘The exact short time propagator, in a form similar to the Crank-Nicholson method but in the spirit of spectrally transformed Hamiltonian, was proposed to solve the triatomic reactive time-dependent schrodinger equation. This new propagator is exact and unconditionally convergent for calculating reactive scattering processes with large time step sizes. In order to improve the computational efficiency, the spectral difference method was applied. This resulted the Hamiltonian with elements confined in a narrow diagonal band. In contrast to our previous theoretical work, the discrete variable representation was applied and resulted in full Hamiltonian matrix. As examples, the collision energy-dependent probability of the triatomic H＋H2 and O＋O2 reaction are calculated. The numerical results demonstrate that this new propagator is numerically accurate and capable of propagating the wave packet with large time steps. However, the efficiency and accuracy of this new propagator strongly depend on the mathematical method for solving the involved linear equations and the choice of preconditioner.
基金Supported by the National Natural Science Foundation of China （No. 40671161） and the Open Research Fund Program of the Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, China（No.1469990324233-03-04）.
文摘An algorithm （differential mode） is presented for the improvement of harmonic tidal analysis along T/P tracks, in which the differences between the observed sea surface heights at adjacent points are taken as observations. Also, the observation equations are constrained with the results of the crossover analysis; the parameter estimations are performed at 0.1° latitude intervals by the least squares. Cycle 10 to 330 T/P altimeter data covering the China Sea and the Northwest Pacific Ocean （2°-50° N,105°-150° E） are adopted for a refined along-track harmonic tidal analysis, and harmonic constants of 12 constituents in 8 474 points are obtained, which indicates that the algorithm can efficiently remove non-tidal effects in the altimeter observations, and improve the precision of tide parameters. Moreover, parameters along altimetry tracks represent a smoother distribution than those obtained by traditional algorithms. The root mean squares of the fitting errors between the tidal height model and the observations reduce from 11 cm to 1.3 cm.
文摘The Effects of pressure stress work and viscous dissipation in mixed convection flow along a vertical fiat plate have been investigated. The results are obtained by transforming the governing system of boundary layer equations into a system of non-dimensional equations and by applying implicit finite difference method together with Newton＇s linearization approximation. Numerical results for different values of pressure stress work parameter, viscous dissipation parameter and Prandtl number have been obtained. The velocity profiles, temperature distributions, skin friction co-efficient and the rate of heat transfer have been presented graphically for the effects of the aforementioned parameters.
文摘With the increasing researches on geotechnical properties of the diesel contaminated soil( DCS),the water content measured is indispensable part during the early period. In this study,the relative error of water content measurement using the traditional method is as high as 20. 78%,which is no longer suitable for contaminated soil. Through a series of tests to measure the loss coefficient of diesel in the drying time,the authors finally proposed a modified calculation formula for test samples. The results show that the maximum relative error calculated by using the modified formula is 0. 96%,far lower than that of traditional formula,which can provide accurate data for further study of diesel contaminated soil.
文摘A numerical study has been carried out to investigate the effect of aspect ratio on heat transfer by natural convection of nanofluid taking Cu nano particles and the water as based fluid. The flow is laminar, steady state, axisymmetric two-dimensional in a vertical cylindrical channel filled with porous media. Heat is generated uniformly along the center of the channel with its vertical surface remain with cooled constant wall temperature and insulated horizontal top and bottom surfaces. The governing equations which used are continuity, momentum and energy equations using Darcy law and Boussinesq＇s approximation which are transformed to dimensionless equations. The finite difference approach is used to obtain all the computational results using the MATLAB-7 program. The parameters affected on the system are Rayleigh number ranging within （10≤ Ra ≤ 103）, aspect ratio （1 ≤ As 〈 5） and the volume fraction （0 ≤0 〈 0.2）. The results obtained are presented graphically in the form of streamline and isotherm contour plots and the results show that as ~ increase from 0.01 to 0.2 the value of the mean Nusselt number increase 50.4% for Ra = 1,000.
基金supported by Natural Science Foundation of China (Grant No. 10871044)
文摘This article is devoted to the study of high order accuracy difference methods tor the Cahn-rnmara equation. A three level linearized compact difference scheme is derived. The u^ique solvability and uaconditional convergence of the difference solution are proved. The convergence order is O（T2＋h4） in the maximum norm. The mass conservation and the non-increase of the total energy are also verified. Some numerical examples are given to demonstrate the theoretical results.
基金supported by the National Natural Science Foundation of China(Grant No.11272252)
文摘A high-speed digital camera is used to record the saltation of three sand samples(diameter range:300–500,200–300 and100–125μm).This is followed by an overlapping particle tracking algorithm to reconstruct the saltating trajectory and the differential scheme to abstract the kinetic parameters of saltating grains.The velocity results confirm the propagating feature of saltation in maintaining near-face aeolian sand transport.Moreover,the acceleration of saltating sand grains was obtained directly from the reconstructed trajectory,and the results reveal that the climbing stage of the saltating trajectory represents an critical process of energy transfer while the sand grains travel through air.
