Automatic Vehicle License Recognition Based on Video Vehicular Detection System

Traditional methods of license character extraction cannot meet the requirements of recognition accuracy and speed rendered by the video vehicular detection system. Therefore, a license plate localization method based on multi-scale edge detection and a character segmentation algorithm based on Markov random field model is presented. Results of experiments demonstrate that the method yields more accurate license character extraction in contrast to traditional localization method based on edge detection by difference operator and character segmentation based on threshold. The accuracy increases from 90% to 94% under preferable illumination, while under poor condition, it increases more than 5%. When the two improved algorithms are used, the accuracy and speed of automatic license recognition meet the system＇s requirement even under the noisy circumstance or uneven illumination.

Aluminum Alloy Material Structure Impact Localization by Using FBG Sensors

The aluminum alloy structure impact localization system by using fiber Bragg grating （FBG） sensors and impact localization algorithm was investigated. A four-FBG sensing network was established. And the power intensity demodulation method was initialized employing the narrow-band tunable laser. The wavelet transform was used to weaken the impact signal noise. And the impact signal time difference was extracted to build the time difference localization algorithm. At last, a fiber Bragg grating impact localization system was established and experimentally verified. The experimental results showed that in the aluminum alloy plate with the 500mm＊500mm＊2mm test area, the maximum and average impact abscissa localization errors were 11 mm and 6.25mm, and the maximum and average impact ordinate localization errors were 9 mm and 4.25 mm, respectively. The fiber Bragg grating sensors and demodulation system are feasible to realize the aviation aluminum alloy material structure impact localization. The research results provide a reliable method for the aluminum alloy material structure impact localization.

Theoretical Modeling and Analysis of Vibroacoustic Characteristics of an Acoustic Metamaterial Plate

Locally resonant metamaterial plates with subwavelength bandgaps can be exploited for the simultaneous control of structural vibrations and acoustic radiation.The present work theoretically investigates the vibroacoustic characteristics of a metamaterial plate with periodic lateral local resonance.The high accuracy of the presented method is evident from the consistency of the cross mobility of the metamaterial plate calculated with the finite element technique.The modal superposition approach and Rayleigh integral technique are adopted to formulate the mean square velocity and acoustic radiation power in terms of the structural deflection and sound pressure to capture the vibroacoustic coupling characteristics of the metamaterial plate and the surrounding environment.Large vibration suppression and sound reduction with high radiation efficiency can be observed within the frequency ranges of interest.The near-field sound intensity and far-field acoustic pressure distributions inside and outside the bandgaps are plotted and analyzed.The results from this work can be utilized to set design guidelines for metamaterial design to achieve prescribed vibroacoustic characteristics.