This paper describes two modified methods for triangular and quadrilateral meshing for finite element analysis of 2D electric machines. One is coupling the classic Delaunay method and advancing front method to generat...This paper describes two modified methods for triangular and quadrilateral meshing for finite element analysis of 2D electric machines. One is coupling the classic Delaunay method and advancing front method to generate optimal triangulation; the other is coupling the classic paving and Delaunay triangulation for optimal quadrilateral meshing. Various electric machine models are meshed successfully to demonstrate the robustness and effectiveness of the methods.展开更多
Conventional f-x prediction filtering methods are based on an autoregressive model. The error section is first computed as a source noise but is removed as additive noise to obtain the signal, which results in an assu...Conventional f-x prediction filtering methods are based on an autoregressive model. The error section is first computed as a source noise but is removed as additive noise to obtain the signal, which results in an assumption inconsistency before and after filtering. In this paper, an autoregressive, moving-average model is employed to avoid the model inconsistency. Based on the ARMA model, a noncasual prediction filter is computed and a self-deconvolved projection filter is used for estimating additive noise in order to suppress random noise. The 1-D ARMA model is also extended to the 2-D spatial domain, which is the basis for noncasual spatial prediction filtering for random noise attenuation on 3-D seismic data. Synthetic and field data processing indicate this method can suppress random noise more effectively and preserve the signal simultaneously and does much better than other conventional prediction filtering methods.展开更多
To study wave-current actions on 3-D bodies a time-domain numerical model was established using a higher-order boundary element method(HOBEM).By assuming small flow velocities,the velocity potential could be expressed...To study wave-current actions on 3-D bodies a time-domain numerical model was established using a higher-order boundary element method(HOBEM).By assuming small flow velocities,the velocity potential could be expressed for linear and higher order components by perturbation expansion.A 4th-order Runge-Kutta method was applied for time marching.An artificial damping layer was adopted at the outer zone of the free surface mesh to dissipate scattering waves.Validation of the numerical method was carried out on run-up,wave exciting forces,and mean drift forces for wave-currents acting on a bottom-mounted vertical cylinder.The results were in close agreement with the results of a frequency-domain method and a published time-domain method.The model was then applied to compute wave-current forces and run-up on a Seastar mini tension-leg platform.展开更多
To test the accuracy of real-time three-dimensional echocardiography (RT3DE) imaging system for evaluating left ventricular mass (LVM) in phantom and excised canine heart. Methods Ten left ventricular (LV) wall phanto...To test the accuracy of real-time three-dimensional echocardiography (RT3DE) imaging system for evaluating left ventricular mass (LVM) in phantom and excised canine heart. Methods Ten left ventricular (LV) wall phantoms made of two rubber-bursas, ten excised canine hearts underwent RT3DE and two-dimensional echocardiography (2DE). In RT3DE "full volume" imaging, the myocardial volume was mea-sured using 2,4,8, and 16-plane method with the analysis software of RT3DE. Mass was then calculated by multiplying the resulting myocardial volume by specific density of myocardial tissue. In 2DE the masses were measured by area-length meth-od. The true LV wall phantom mass was measured by water displacement and the canine LVM was weighed by anatomy, which served as a reference standard. We compared RT3DE or 2DE with true mass. Results In LV wall phantoms, RT3DE correlated with true masses strongly (r = 0.813-0.994) and weakly correlated between 2DE and true masses (r = 0.628). In excised canine hearts, there is an excellent correlation between RT3DE and true masses (r = 0.764-0.991), while 2DE value showed a lesser correlation (r = 0.514). There are no difference between RT-3DE and true masses (P > 0.05) but different between 2DE and true masses (P < 0.05). In different planes, there was no difference between 8-plane and 16-plane (P > 0.05) but different between 8-plane and 2, 4-plane (P < 0.05). Conclusion RT3DE can accurately quantify LVM and provide a new tool to evaluate LV function. For LVM by RT3DE, 8-plane measurement method is the best choice for accuracy and convenience.展开更多
The compound KdV-Burgers equation and combined KdV-mKdV equation are real physical models concerning many branches in physics.In this paper,applying the improved trigonometric function method to these equations,rich e...The compound KdV-Burgers equation and combined KdV-mKdV equation are real physical models concerning many branches in physics.In this paper,applying the improved trigonometric function method to these equations,rich explicit and exact travelling wave solutions,which contain solitary-wave solutions,periodic solutions,and combined formal solitary-wave solutions,are obtained.展开更多
In this paper a 3D numerical model was developed to study the complicated interaction between waves and a set of tandem fixed cylinders.The fluid was considered to be inviscid and irrotational.Therefore,the Helmholtz ...In this paper a 3D numerical model was developed to study the complicated interaction between waves and a set of tandem fixed cylinders.The fluid was considered to be inviscid and irrotational.Therefore,the Helmholtz equation was used as a governing equation.The boundary element method（BEM） was adopted to discretize the relevant equations.Open boundaries were used in far fields of the study domain.Linear waves were generated and propagated towards tandem fixed cylinders to estimate the forces applied on them.Special attention was paid to consideration of the effect on varying non-dimensional cylinder radius and distance between cylinders,ka and kd on forces and trapped modes.The middle cylinder wave forces and trapped modes in a set of nine tandem cylinders were validated utilizing analytical data.The comparisons confirm the accuracy of the model.The results of the inline wave force estimation on n tandem cylinders show that the critical cylinder in the row is the middle one for odd numbers of cylinders.Furthermore the results show that the critical trapped mode effect occurs for normalized cylinder radiuses close to 0.5 and 1.0.Finally the force estimation for n tandem cylinders confirms that force amplitude of the middle cylinder versus normalized separation distance fluctuates about that of a single cylinder.展开更多
In the traditional dual-frequency radar ranging system,there is a contradiction between ranging precision and ranging distance.So a tri-frequency ranging method is proposed.The principle of the tri-frequency ranging i...In the traditional dual-frequency radar ranging system,there is a contradiction between ranging precision and ranging distance.So a tri-frequency ranging method is proposed.The principle of the tri-frequency ranging is that the distance can be achieved by transmitting the three frequencies and then measuring the three phase difference and calculating the number of wavelength.What's more,range ambiguity will not occur within a certain distance.The experimental results show that,if the waveband is 0.47 ~0.57 m,the measurement of unambiguous distance of 25 ~500m can be realized.If the wavelength tolerance error is less than ± 10^(-7) and the phase error is less than ± 10^(-3),the precision of the distance ranging can reach 10^(-6).展开更多
文摘This paper describes two modified methods for triangular and quadrilateral meshing for finite element analysis of 2D electric machines. One is coupling the classic Delaunay method and advancing front method to generate optimal triangulation; the other is coupling the classic paving and Delaunay triangulation for optimal quadrilateral meshing. Various electric machine models are meshed successfully to demonstrate the robustness and effectiveness of the methods.
基金This research was financially supported by National Natural Science Foundation of China （Grant No. 40604016） and the National Hi-Tech Research and Development Program （863 Program） （Grants No. 2006AA09A102-09 and No. 2007AA06Z229）.
文摘Conventional f-x prediction filtering methods are based on an autoregressive model. The error section is first computed as a source noise but is removed as additive noise to obtain the signal, which results in an assumption inconsistency before and after filtering. In this paper, an autoregressive, moving-average model is employed to avoid the model inconsistency. Based on the ARMA model, a noncasual prediction filter is computed and a self-deconvolved projection filter is used for estimating additive noise in order to suppress random noise. The 1-D ARMA model is also extended to the 2-D spatial domain, which is the basis for noncasual spatial prediction filtering for random noise attenuation on 3-D seismic data. Synthetic and field data processing indicate this method can suppress random noise more effectively and preserve the signal simultaneously and does much better than other conventional prediction filtering methods.
基金Supported by the National Natural Science Foundation of China under (Grant No.107 72040,50709005 and 50921001)the Major National Science and Technology Projects of China under (Grant No.2008ZX05026-02)the Open Fund of State Key Laboratory of Ocean Engineering
文摘To study wave-current actions on 3-D bodies a time-domain numerical model was established using a higher-order boundary element method(HOBEM).By assuming small flow velocities,the velocity potential could be expressed for linear and higher order components by perturbation expansion.A 4th-order Runge-Kutta method was applied for time marching.An artificial damping layer was adopted at the outer zone of the free surface mesh to dissipate scattering waves.Validation of the numerical method was carried out on run-up,wave exciting forces,and mean drift forces for wave-currents acting on a bottom-mounted vertical cylinder.The results were in close agreement with the results of a frequency-domain method and a published time-domain method.The model was then applied to compute wave-current forces and run-up on a Seastar mini tension-leg platform.
文摘To test the accuracy of real-time three-dimensional echocardiography (RT3DE) imaging system for evaluating left ventricular mass (LVM) in phantom and excised canine heart. Methods Ten left ventricular (LV) wall phantoms made of two rubber-bursas, ten excised canine hearts underwent RT3DE and two-dimensional echocardiography (2DE). In RT3DE "full volume" imaging, the myocardial volume was mea-sured using 2,4,8, and 16-plane method with the analysis software of RT3DE. Mass was then calculated by multiplying the resulting myocardial volume by specific density of myocardial tissue. In 2DE the masses were measured by area-length meth-od. The true LV wall phantom mass was measured by water displacement and the canine LVM was weighed by anatomy, which served as a reference standard. We compared RT3DE or 2DE with true mass. Results In LV wall phantoms, RT3DE correlated with true masses strongly (r = 0.813-0.994) and weakly correlated between 2DE and true masses (r = 0.628). In excised canine hearts, there is an excellent correlation between RT3DE and true masses (r = 0.764-0.991), while 2DE value showed a lesser correlation (r = 0.514). There are no difference between RT-3DE and true masses (P > 0.05) but different between 2DE and true masses (P < 0.05). In different planes, there was no difference between 8-plane and 16-plane (P > 0.05) but different between 8-plane and 2, 4-plane (P < 0.05). Conclusion RT3DE can accurately quantify LVM and provide a new tool to evaluate LV function. For LVM by RT3DE, 8-plane measurement method is the best choice for accuracy and convenience.
文摘The compound KdV-Burgers equation and combined KdV-mKdV equation are real physical models concerning many branches in physics.In this paper,applying the improved trigonometric function method to these equations,rich explicit and exact travelling wave solutions,which contain solitary-wave solutions,periodic solutions,and combined formal solitary-wave solutions,are obtained.
文摘In this paper a 3D numerical model was developed to study the complicated interaction between waves and a set of tandem fixed cylinders.The fluid was considered to be inviscid and irrotational.Therefore,the Helmholtz equation was used as a governing equation.The boundary element method（BEM） was adopted to discretize the relevant equations.Open boundaries were used in far fields of the study domain.Linear waves were generated and propagated towards tandem fixed cylinders to estimate the forces applied on them.Special attention was paid to consideration of the effect on varying non-dimensional cylinder radius and distance between cylinders,ka and kd on forces and trapped modes.The middle cylinder wave forces and trapped modes in a set of nine tandem cylinders were validated utilizing analytical data.The comparisons confirm the accuracy of the model.The results of the inline wave force estimation on n tandem cylinders show that the critical cylinder in the row is the middle one for odd numbers of cylinders.Furthermore the results show that the critical trapped mode effect occurs for normalized cylinder radiuses close to 0.5 and 1.0.Finally the force estimation for n tandem cylinders confirms that force amplitude of the middle cylinder versus normalized separation distance fluctuates about that of a single cylinder.
基金Supported by the National Natural Science Foundation of China(No.61107052)the National Natural Science Foundation of Tianjing(No.11JCYBJC00100)
文摘In the traditional dual-frequency radar ranging system,there is a contradiction between ranging precision and ranging distance.So a tri-frequency ranging method is proposed.The principle of the tri-frequency ranging is that the distance can be achieved by transmitting the three frequencies and then measuring the three phase difference and calculating the number of wavelength.What's more,range ambiguity will not occur within a certain distance.The experimental results show that,if the waveband is 0.47 ~0.57 m,the measurement of unambiguous distance of 25 ~500m can be realized.If the wavelength tolerance error is less than ± 10^(-7) and the phase error is less than ± 10^(-3),the precision of the distance ranging can reach 10^(-6).
