The performance of a sonar system is closely related to the marine environment and the target characteristics. When dealing with the echoes of a traditional active sonar system, the sonar designers often do not take i...The performance of a sonar system is closely related to the marine environment and the target characteristics. When dealing with the echoes of a traditional active sonar system, the sonar designers often do not take into account the influence of the environmental information and prior knowledge perceived by sonar receivers, making it difficult to obtain desired processing results. Based on the basic principle and key technology of sonar, this paper proposed a cognition-based intelligent sonar system in theory--cognitive sonar. Cognitive sonar is capable of jointly optimizing the transmission waveform and receiver according to the changes of environment so that its detection and identification performance can be significantly improved.展开更多
The effect of Zn dopant on the growth of cadmium oxide （CdO） nanostructures through a sonochemical method wasinvestigated. The X-ray diffraction （XRD） patterns of the nanoparticles show CdO cubic structures for th...The effect of Zn dopant on the growth of cadmium oxide （CdO） nanostructures through a sonochemical method wasinvestigated. The X-ray diffraction （XRD） patterns of the nanoparticles show CdO cubic structures for the produced samples. Fieldemission scanning electron microscope （FESEM） images reveal that morphologies of the samples change, when they are doped withZn atoms, and their sizes reduce. Room temperature photoluminescence （PL） and UV-Vis spectrometers were used to study opticalproperties of the samples. Evaluation of optical properties indicates that different emission bands result from different transitions andthe value of CdO energy band gap increases due to doping. Studies of electrical properties of the nanostructures demonstrate that Zndopant enhances electrical conductivity and photocurrent generation as the result of light illumination on the nanostructures due toimproved density of photo-generated carriers. Considering the obtained outcomes, Zn dopant can alter the physical property of theCdO nanostructures.展开更多
The absorption of sound in the low frequency range is problematic with fibrous materials made up of coarser fibers. In that case, highly efficient sound absorption materials from much finer fibers must be developed. A...The absorption of sound in the low frequency range is problematic with fibrous materials made up of coarser fibers. In that case, highly efficient sound absorption materials from much finer fibers must be developed. Although studies on the acoustic properties of conventional textile materials started in the nineties, analysis of the acoustic properties of the electrospun nanofibrous membranes is a novel subject. Nanofibrous membranes can improve acoustic insulation products by increasing the sound absorption coefficient, reducing material thickness, and decreasing material weight offering a competitive advantage. The purpose of this study is to analyze the effect of fiber diameter on the acoustic behavior of nanofibrous membranes.展开更多
基金Supported by Research Foundation of Shaanxi Province Returned Overseas Students No.SLZ2008006
文摘The performance of a sonar system is closely related to the marine environment and the target characteristics. When dealing with the echoes of a traditional active sonar system, the sonar designers often do not take into account the influence of the environmental information and prior knowledge perceived by sonar receivers, making it difficult to obtain desired processing results. Based on the basic principle and key technology of sonar, this paper proposed a cognition-based intelligent sonar system in theory--cognitive sonar. Cognitive sonar is capable of jointly optimizing the transmission waveform and receiver according to the changes of environment so that its detection and identification performance can be significantly improved.
基金Ahvaz Branch, Islamic Azad University for the financial support in this research work
文摘The effect of Zn dopant on the growth of cadmium oxide （CdO） nanostructures through a sonochemical method wasinvestigated. The X-ray diffraction （XRD） patterns of the nanoparticles show CdO cubic structures for the produced samples. Fieldemission scanning electron microscope （FESEM） images reveal that morphologies of the samples change, when they are doped withZn atoms, and their sizes reduce. Room temperature photoluminescence （PL） and UV-Vis spectrometers were used to study opticalproperties of the samples. Evaluation of optical properties indicates that different emission bands result from different transitions andthe value of CdO energy band gap increases due to doping. Studies of electrical properties of the nanostructures demonstrate that Zndopant enhances electrical conductivity and photocurrent generation as the result of light illumination on the nanostructures due toimproved density of photo-generated carriers. Considering the obtained outcomes, Zn dopant can alter the physical property of theCdO nanostructures.
文摘The absorption of sound in the low frequency range is problematic with fibrous materials made up of coarser fibers. In that case, highly efficient sound absorption materials from much finer fibers must be developed. Although studies on the acoustic properties of conventional textile materials started in the nineties, analysis of the acoustic properties of the electrospun nanofibrous membranes is a novel subject. Nanofibrous membranes can improve acoustic insulation products by increasing the sound absorption coefficient, reducing material thickness, and decreasing material weight offering a competitive advantage. The purpose of this study is to analyze the effect of fiber diameter on the acoustic behavior of nanofibrous membranes.
