High-precision ultrasound imaging of void defects is critical for the performance and safety assessment of ballastless track structures. The sound propagation velocity of each layer in the ballastless track structure ...
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High-precision ultrasound imaging of void defects is critical for the performance and safety assessment of ballastless track structures. The sound propagation velocity of each layer in the ballastless track structure is quite different. However, the traditional concrete Synthetic Aperture Focusing Technique (SAFT) ultrasound imaging method is based on the assumption that the concrete has a single constant shear wave velocity. Thus, it is not a suitable method for the ultrasonic imaging of multilayer structures. In this paper, a Multilayer SAFT high-precision ultrasound imaging method is proposed. It is based on the ray-tracing technique and uses the Fermat principle to find the refraction point that minimizes the delay of the acoustic wave propagation path at the interface of the discrete layers. Then, the acoustic wave propagation path is segmented by the position of the refraction point, and the propagation delay of the ultrasonic wave is obtained segment by segment. Thus, the propagation delay of the ultrasonic wave is obtained one by one, so that the propagation delay of the ultrasonic wave in the multilayer structure can be accurately obtained. Finally, the focused image is obtained according to the SAFT imaging algorithm. The finite element simulation and experimental results show that the Multilayer SAFT imaging method can accurately track the propagation path of the ultrasonic wave in ballastless track structures, as well as accurately calculate the propagation delay of the ultrasonic wave and the lengths of void defects. The high accuracy of the Multilayer SAFT imaging represents a significant improvement compared to traditional SAFT imaging.
Elderly and patients with abnormalities in the control of body movement need automatic alarm with privacy protection when they fall, this paper proposes octagonal formation of ultrasonic array sensors for fall detecti...
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ISBN:
(纸本)9781509024018
Elderly and patients with abnormalities in the control of body movement need automatic alarm with privacy protection when they fall, this paper proposes octagonal formation of ultrasonic array sensors for fall detection system in a smart room. In the method, octagonal array is designed to install ultrasonicsensors on a wall and roof. Signals of ultrasonic reflected from object in the room are processed to recognize fall. In experiments, the proposed method is proved 94% accuracy in fall detection
a new partial discharge (PD) number estimation method in oil is presented based on ultrasonic array sensors and modified CCT in this paper. Firstly, ultrasonic array sensors are developed which can receive and format ...
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ISBN:
(纸本)9781424448135
a new partial discharge (PD) number estimation method in oil is presented based on ultrasonic array sensors and modified CCT in this paper. Firstly, ultrasonic array sensors are developed which can receive and format the wideband arrayultrasonic signal of PD. Secondly, sub-band averaging and CCT are applied to realize PD number estimation in Oil. Lastly, the results of experimental research indicate that the method is effective. When the source numbers are 1, 2, 3 respectively, the estimated probability of success are 90%, 83% and 72%.
We present a zoned presence detection system using multiple ultrasonic array sensors. In active mode, sensors transmit consecutive bursts of sinusoidal pulses over a transmission slot in a time-division multiplexed ma...
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We present a zoned presence detection system using multiple ultrasonic array sensors. In active mode, sensors transmit consecutive bursts of sinusoidal pulses over a transmission slot in a time-division multiplexed manner. We present a transmission slot synchronization method to maintain assigned transmission slots of each sensor. The proposed method is distributed and does not rely on a central coordinator or unique identifiers for the sensors. In a transmission slot, the corresponding receiver array uses moving target processing on received echoes to derive range and direction-of-arrival, defining a zone. A tracking algorithm is used to make the zoned presence detection more robust. The presented methods are evaluated using ceiling-installed ultrasonic linear arraysensors in an experimental office setup.
Transformer partial discharge ultrasonicarray detection method is a new method with high signal-to-noise ratio and high reliability. But the influence of array number to the direction finding accuracy needs to be fur...
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ISBN:
(纸本)9783038350033
Transformer partial discharge ultrasonicarray detection method is a new method with high signal-to-noise ratio and high reliability. But the influence of array number to the direction finding accuracy needs to be further studied. Simulation of direction finding angle with the 15 kinds of sensor array ( 2 x 2 - 16x16 arrangement)under two conditions of the acute azimuth and obtuse azimuth, study of change rule of direction finding accuracy of the different array number, for example of the square planar array sensor, based on an improved MUSIC(Multiple Signal Classification) algorithm. The results show that the direction finding accuracy increases as the array number rises, and The specific error ranges of arraysensors of different array number by simulating have some degree of guiding significance in the selection of transformer partial discharge ultrasonic a(r)ray sensor in the field environment.
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