The first- and second-order statistical properties of ultrasound -speckles reflected from an interface are studied theoretically and experimentally. A theoretical model for predicting statistical properties of ultraso...The first- and second-order statistical properties of ultrasound -speckles reflected from an interface are studied theoretically and experimentally. A theoretical model for predicting statistical properties of ultrasound speckles is constructed based on the Fresnel-Huygens principle and three basic assumptions. Distributions of amplitude and phase of ultrasound speckles in a scattering space are studied. And the study shows that they are in the form of Rayleigh and uniform distribution respectively. Using the proposed model, the average transverse size of the speckles within a scattering domain which are received by a focus probe is investigated. The average transverse size is found to be dependent on the characteristics of the measuring system only, and does not vary with the position in the domain. To verify the applicability of the theoretical model, a special experimental set-up was designed and the corresponding experiments were conducted for measuring the sound pressure of the ultrasound speckles reflected from an interface between water and Aluminium alloy. The numerical results are compared with the experimental ones. The comparison demonstrates that the theoretical model and the three related assumptions are suitable for analysing statistical properties of ultrasound speckles reflected from an interface.展开更多
Trade deficit has provided international trade protection forces with a grand excuse. e US and EU sides are prone to either imposing anti-dumping on China, or demanding revaluation of the Renminbi (RMB) under the pret...Trade deficit has provided international trade protection forces with a grand excuse. e US and EU sides are prone to either imposing anti-dumping on China, or demanding revaluation of the Renminbi (RMB) under the pretext of trade deficit. Many businessmen claimed that they have suffered great losses whenever trade deficit is mentioned.展开更多
基金This work was supported by the National Natural Science Foundation of China (10074017).
文摘The first- and second-order statistical properties of ultrasound -speckles reflected from an interface are studied theoretically and experimentally. A theoretical model for predicting statistical properties of ultrasound speckles is constructed based on the Fresnel-Huygens principle and three basic assumptions. Distributions of amplitude and phase of ultrasound speckles in a scattering space are studied. And the study shows that they are in the form of Rayleigh and uniform distribution respectively. Using the proposed model, the average transverse size of the speckles within a scattering domain which are received by a focus probe is investigated. The average transverse size is found to be dependent on the characteristics of the measuring system only, and does not vary with the position in the domain. To verify the applicability of the theoretical model, a special experimental set-up was designed and the corresponding experiments were conducted for measuring the sound pressure of the ultrasound speckles reflected from an interface between water and Aluminium alloy. The numerical results are compared with the experimental ones. The comparison demonstrates that the theoretical model and the three related assumptions are suitable for analysing statistical properties of ultrasound speckles reflected from an interface.
文摘Trade deficit has provided international trade protection forces with a grand excuse. e US and EU sides are prone to either imposing anti-dumping on China, or demanding revaluation of the Renminbi (RMB) under the pretext of trade deficit. Many businessmen claimed that they have suffered great losses whenever trade deficit is mentioned.
