Scatterers often exhibit aspect or frequency dependence which affects the micro-Doppler shift in scattering response. For cone-cylinder targets, sliding-type scatterers which slide on the edge discontinuity with the c...Scatterers often exhibit aspect or frequency dependence which affects the micro-Doppler shift in scattering response. For cone-cylinder targets, sliding-type scatterers which slide on the edge discontinuity with the change of the incident angle are the most dominant nonideal scattering models. A method is proposed to discriminate among the scatterers on the cone-cylinder target based on the deviation degree of micro-Doppler from sinusoid. By extracting the amplitude and initial phase, the micro-Doppler is estimated as sinusoid. Then the deviation degree is evaluated by the error between the extracted sinusoidal micro-Doppler and the actual micro-Doppler curve. Threshold for the classification is determined with the simulation data. After classification, the micro-Doppler features of sliding-type scatterers are exploited to estimate the target dimensions. The influence of parameters errors and noise on estimation of target dimensions is also illustrated with the simulation data. ? 1990-2011 Beijing Institute of Aerospace Information.展开更多
The buckling propagation in marine pipelines is studied by means of the cylindrical shell model in this paper. Several parameters including geometrical parameter D/ T, L/ D, physical parameter E and σy are discussed....The buckling propagation in marine pipelines is studied by means of the cylindrical shell model in this paper. Several parameters including geometrical parameter D/ T, L/ D, physical parameter E and σy are discussed. The computed results are compared with the available experimental data and other computed results, it is found that the present are closer to the experimental results than other computed results.展开更多
For better controllability in actuations,it is desirable to create Functionally Graded Shape Memory Alloys（FG-SMAs）in the actuation direction.It can be achieved by applying different heat treatment processes to crea...For better controllability in actuations,it is desirable to create Functionally Graded Shape Memory Alloys（FG-SMAs）in the actuation direction.It can be achieved by applying different heat treatment processes to create the gradient along the radius of a SMA cylinder.Analytical solutions are derived to predict the macroscopic behaviors of such a functionally graded SMA cylinder.The Tresca yield criterion and linear hardening are used to describe the different phase transformations with different gradient parameters.The numerical results for an example of the model exhibit different pseudo-elastic behaviors from the non-gradient case,as well as a variational hysteresis loop for the transformation,providing a mechanism for easy actuation control.When the gradient disappears,the model can degenerate to the non-gradient case.展开更多
The fluctuating pressures on the surface of three circular cylinders in equispaced arrangement were measured simultaneously in the medium subcritical regime (Re=3×104). The distributions of their rms values and c...The fluctuating pressures on the surface of three circular cylinders in equispaced arrangement were measured simultaneously in the medium subcritical regime (Re=3×104). The distributions of their rms values and circumferential correlation were obtained in the spacing range from 1.25 to 6.0. The spatial correlation of pressures of two pressure taps on two different cylinders at the same azimuth was investigated as well. Owing to different flow patterns in various arrangements and spacing, these correlation curves of pressure show different distributions. The lift fluctuation can be estimated qualitatively from the circumferential coefficient curve with the knowledge of the rms pressure distribution. Some critical spacing for each arrangement were found that the flow regimes and the corresponding pressure correlation take a sudden change. Flow interference between cylinders in each arrangement was also discussed with various flow regimes.展开更多
This paper presents the model test to measure the second-order wave pressure and forces on a circular cylinder fixed in Stokes wave with a given draught. The distributions of second-order oscillating and steady wave p...This paper presents the model test to measure the second-order wave pressure and forces on a circular cylinder fixed in Stokes wave with a given draught. The distributions of second-order oscillating and steady wave pressure on the wet surface of the cylinder and second order oscillating wave forces were obtained in this test, but the second-order steady wave force was not able to be measured due to its very small magnitude. The test results also show that third-order wave force may be greater than the second-order force when wave frequencies are high. The experimental results were compared with the corresponding calculation results of Reference [3].展开更多
The equations of motion for rapid flow of a granular material were derived and their solutions representing flow driven by a body force along an infinitely-long cylinder were obtained by the numerical method.
In the present paper an unsteady flow of polymer fluid, i.e. non-Newtonian fluid is studied. The constitutive equation of upper-convected Maxwell fluid is used. The variational approach due to Kantorovich is used for ...In the present paper an unsteady flow of polymer fluid, i.e. non-Newtonian fluid is studied. The constitutive equation of upper-convected Maxwell fluid is used. The variational approach due to Kantorovich is used for the unsteady problem of the fluid. A special computer program `MACSYMA' is used to get the different approximation of the method of Kantorovich. The present method developed is called Computational Analytical Method which is available for the scientific research.展开更多
The solution of boundary layer along a curved surface was discussed in this article. According to the principle of the theory of similarity, the method of partial similarity was proposed, in which the profile of objec...The solution of boundary layer along a curved surface was discussed in this article. According to the principle of the theory of similarity, the method of partial similarity was proposed, in which the profile of object is divided into many tiny sections, the method of similarity was used in each section and the error in each section was fully considered. This method is proved to be feasible.展开更多
基金supported by the National Natural Science Foundation of China(61271442)
文摘Scatterers often exhibit aspect or frequency dependence which affects the micro-Doppler shift in scattering response. For cone-cylinder targets, sliding-type scatterers which slide on the edge discontinuity with the change of the incident angle are the most dominant nonideal scattering models. A method is proposed to discriminate among the scatterers on the cone-cylinder target based on the deviation degree of micro-Doppler from sinusoid. By extracting the amplitude and initial phase, the micro-Doppler is estimated as sinusoid. Then the deviation degree is evaluated by the error between the extracted sinusoidal micro-Doppler and the actual micro-Doppler curve. Threshold for the classification is determined with the simulation data. After classification, the micro-Doppler features of sliding-type scatterers are exploited to estimate the target dimensions. The influence of parameters errors and noise on estimation of target dimensions is also illustrated with the simulation data. ? 1990-2011 Beijing Institute of Aerospace Information.
文摘The buckling propagation in marine pipelines is studied by means of the cylindrical shell model in this paper. Several parameters including geometrical parameter D/ T, L/ D, physical parameter E and σy are discussed. The computed results are compared with the available experimental data and other computed results, it is found that the present are closer to the experimental results than other computed results.
基金the financial support of National Natural Science Foundation of China (no.11502284, 51505483, 11772041)the Fundamental Research Funds for the Central Universities (3122016C006) of China
文摘For better controllability in actuations,it is desirable to create Functionally Graded Shape Memory Alloys（FG-SMAs）in the actuation direction.It can be achieved by applying different heat treatment processes to create the gradient along the radius of a SMA cylinder.Analytical solutions are derived to predict the macroscopic behaviors of such a functionally graded SMA cylinder.The Tresca yield criterion and linear hardening are used to describe the different phase transformations with different gradient parameters.The numerical results for an example of the model exhibit different pseudo-elastic behaviors from the non-gradient case,as well as a variational hysteresis loop for the transformation,providing a mechanism for easy actuation control.When the gradient disappears,the model can degenerate to the non-gradient case.
文摘The fluctuating pressures on the surface of three circular cylinders in equispaced arrangement were measured simultaneously in the medium subcritical regime (Re=3×104). The distributions of their rms values and circumferential correlation were obtained in the spacing range from 1.25 to 6.0. The spatial correlation of pressures of two pressure taps on two different cylinders at the same azimuth was investigated as well. Owing to different flow patterns in various arrangements and spacing, these correlation curves of pressure show different distributions. The lift fluctuation can be estimated qualitatively from the circumferential coefficient curve with the knowledge of the rms pressure distribution. Some critical spacing for each arrangement were found that the flow regimes and the corresponding pressure correlation take a sudden change. Flow interference between cylinders in each arrangement was also discussed with various flow regimes.
文摘This paper presents the model test to measure the second-order wave pressure and forces on a circular cylinder fixed in Stokes wave with a given draught. The distributions of second-order oscillating and steady wave pressure on the wet surface of the cylinder and second order oscillating wave forces were obtained in this test, but the second-order steady wave force was not able to be measured due to its very small magnitude. The test results also show that third-order wave force may be greater than the second-order force when wave frequencies are high. The experimental results were compared with the corresponding calculation results of Reference [3].
文摘The equations of motion for rapid flow of a granular material were derived and their solutions representing flow driven by a body force along an infinitely-long cylinder were obtained by the numerical method.
文摘In the present paper an unsteady flow of polymer fluid, i.e. non-Newtonian fluid is studied. The constitutive equation of upper-convected Maxwell fluid is used. The variational approach due to Kantorovich is used for the unsteady problem of the fluid. A special computer program `MACSYMA' is used to get the different approximation of the method of Kantorovich. The present method developed is called Computational Analytical Method which is available for the scientific research.
文摘The solution of boundary layer along a curved surface was discussed in this article. According to the principle of the theory of similarity, the method of partial similarity was proposed, in which the profile of object is divided into many tiny sections, the method of similarity was used in each section and the error in each section was fully considered. This method is proved to be feasible.
