The determination of the relative permittivity of periodic stratified media based on the iterative time-reversal method

Zhang, Zhimin; Wang, Bing‐Zhong; Liang, Mu‐Sheng; Ji, Qing; Song, Gangbing

doi:10.1088/1674-1056/23/4/048403

Cited by 3 publications

(1 citation statement)

References 27 publications

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“…Yan et al [17] established a dynamic mechanical model to actuate the performance of a piezoelectric material bonded to the surface of structures based on the second class of the piezoelectric equation and continuum dynamics. The research group also presented a new method to determine the relative permittivity of periodic stratified media using the iterative time reversal method [18].…”

Section: Introductionmentioning

confidence: 99%

Smart washer—a piezoceramic-based transducer to monitor looseness of bolted connection

Huo

Chen

Kong

et al. 2017

Smart Mater. Struct.

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The safety of a bolted connection, as one of the most common ways of making two or more parts/components work together in engineering structures, is very important in order to ensure the health of the whole structure. However, bolt loosening or pre-load degradation may induce the failure of the bolt connection, threatening the normal operation of the system's structure. As a result, it would be beneficial if the health condition of the bolt connection could be monitored in real time. In this paper, a 'smart washer', fabricated by embedding a piezoceramic patch into two pre-machined flat metal rings, was invented and then introduced as a transducer to detect the looseness of a bolted connection. A simple specimen, which consists of two steel plates connected by a nut, a bolt and two smart washers, was fabricated as the test object to study the performance of the 'smart washers' (SWs). For the specimen, a smart washer was used as an actuator to generate a stress wave, and the other one was used as a sensor to detect the propagated wave that traveled through the interface of the bolted connection. A time reversal method was employed to quantify the energy of the stress wave propagating between the two washers, and thus it was possible to build a relationship between the extent of any pre-loaded degradation of the bolt connection and the response signal of the stress wave traveling between the two washers. In addition, a normalized bolt looseness index was proposed for evaluating the looseness of a bolt connection based on wavelet energy analysis.

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Section: Introductionmentioning

confidence: 99%

Smart washer—a piezoceramic-based transducer to monitor looseness of bolted connection

Huo

Chen

Kong

et al. 2017

Smart Mater. Struct.

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Single frequency spatial power combining using sparse array based on time reversal of electromagnetic wave

Chen¹,

Jiang²,

Zeng³

et al. 2015

Acta Phys. Sin.

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Based on time-reversal (TR) technique, the model of single frequency spatial power combining using sparse array is established. The efficiency function of spatial power combining is defined. The expression for the relationship of the statistical characteristics of combining efficiency at the time of maximum amplitude with the phase error and the number of array elements is derived. The analysis shows that when other parameters are determined, if the phase errors of the array nodes are mutually independent, and obey the uniform distribution to a certain extent, the combing efficiency's mean would not be related to the number of array elements N, but related to the statistic parameter of phase error. The combing efficiency's variance is related to not only the statistic parameter of phase errors, but also N. Once the statistic parameter of phase error is fixed, the greater the value of N, the smaller the variance is. So, in the engineering application, a large number of small power nodes could be used to reduce the phase error's effect. In addition, the influence of phase error on the combining efficiency is investigated by both theoretical analysis and the numerical simulation. The results show that when the array elements work at the same frequency, polarization and antenna type, the parameter of phase error would affect the combing result. The smaller the parameter of phase error, the larger the power of the effective point is, and the more concentrative the effective points' distribution is; the greater the parameter of phase error, the smaller the power of the effective point is, and the more dispersed the effective points' distribution is. It is also seen that even though the phase error occurs, the spatial power combining can still be realized with the time reversal technique. The determination of the phase control precision is the compromise between the requirements and the possibility. The results presented in this paper are useful for developing the microwave weapons with high power and electronic warfare.

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The novel feed forward and decision feedback equalizer structures and improved variable step algorithm

Xue-Yuan¹,

Xiao-Hong²,

Li-Xia³

2015

Acta Phys. Sin.

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Skin effect and dielectric loss in super-long cable will cause nonlinear attenuation at different signal frequency, and in addition, coupling noise and thermal noise also cause signal distortion at the receiver end. These factors seriously affect the signal transmission speed in the super-long cable. Especially, in the field of exploration of shale gas and bed methane, the transmission cable is also used to transport high-precision synchronization pulse signal, and the synchronization pulse must reach the microsecond accuracy, which is used for data phase calibration. A synchronization signal is a high frequency signal, which suffers more severe attenuation and noise interference. At the receiving end, the sync pulse signal will be drowned in the noise environment, and so it is difficult to restore the original signal.#br#Although fiber can achieve a high transfer rate, but the fiber cable cannot transmit power energy; in addition, the tensile strength and heat resistance of the fiber are much worse than copper cable, these weaknesses limit its application in such industry. Therefore, an effective balancing algorithm is necessary to overcome the propagation effects and interference in a super-long copper cable. However, conventional equalization techniques have well-balanced effect for the short-range communications, but for the long-distance communication, they often have poorly balanced results. In order to solve the above problem and improve the long cable signal transmission speed, this paper presents a new balanced portfolio structure; the new structure uses feed-forward equalizer (FFE) as the pre-stage, and decision-feedback equalizer (DFE) as the post stage to form a new structure. The combination structures can effectively utilize the flexibility of FFE and overcome the problem of error diffusion in DFE. By mathematical modeling and simulation, this paper gives the best combination factors. Furthermore, based on the improved structure, a new convergence algorithm is proposed, which uses the arc tangent function combined with three error converge factors to form a converging function, and it has the advantages of fast convergence and steady-state error. Simulation results show that the FFE-DFE combination equalizer has low computational complexity, fast convergence, and strong channel tracking capability; in addition, it can speed up the data processing speed, and better respond to the real variation of the channel. Simulation results show also that the performance is improved by 50% by eliminating inter-symbol interference and noise.#br#The real circuit board based on the new algorithm have been tested in the East China Petroleum Bureau, the test results show that the algorithm can rectify 160 dB signal distortion, and the transmission speed can reach 5 Mbps in 6 dB signal to noise ratio.

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The determination of the relative permittivity of periodic stratified media based on the iterative time-reversal method

Abstract: The determination of the relative permittivity of periodic stratified media based on the iterative time-reversal method *Zhang Zhi-Min(章志敏) a)b) , Wang Bing-Zhong(王秉中) a) † , Liang Mu-Sheng(梁木生) a) , Ji Qing(纪晴) b) , and Song Gang-Bing(宋钢兵) b) a)

Cited by 3 publications

References 27 publications

Smart washer—a piezoceramic-based transducer to monitor looseness of bolted connection

Smart washer—a piezoceramic-based transducer to monitor looseness of bolted connection

Single frequency spatial power combining using sparse array based on time reversal of electromagnetic wave

The novel feed forward and decision feedback equalizer structures and improved variable step algorithm

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The determination of the relative permittivity of periodic stratified media based on the iterative time-reversal method

Abstract: The determination of the relative permittivity of periodic stratified media based on the iterative time-reversal method *Zhang Zhi-Min(章志敏) a)b) , Wang Bing-Zhong(王秉中) a) † , Liang Mu-Sheng(梁木生) a) , Ji Qing(纪 晴) b) , and Song Gang-Bing(宋钢兵) b) a)

Cited by 3 publications

References 27 publications

Smart washer—a piezoceramic-based transducer to monitor looseness of bolted connection

Smart washer—a piezoceramic-based transducer to monitor looseness of bolted connection

Single frequency spatial power combining using sparse array based on time reversal of electromagnetic wave

The novel feed forward and decision feedback equalizer structures and improved variable step algorithm

Contact Info

Product

Resources

About

Abstract: The determination of the relative permittivity of periodic stratified media based on the iterative time-reversal method *Zhang Zhi-Min(章志敏) a)b) , Wang Bing-Zhong(王秉中) a) † , Liang Mu-Sheng(梁木生) a) , Ji Qing(纪晴) b) , and Song Gang-Bing(宋钢兵) b) a)