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The ablation fault of buffer layers in high-voltage cables is a frequent type of cable fault in recent years. However, current detection methods for ablation defects cannot meet the detection requirements of existing cables. In this paper, the ultrasonic detection method for the buffer layer ablation defects in high-voltage cables based on the surface roughness of aluminum sheath is studied for the first time. Firstly, simulated buffer layer ablation experiments under humid conditions are carried out, and the laser confocal microscopy and electrochemical impedance spectroscopy analysis are carried out on the ablated aluminum specimens. It is found that with the increase of ablation time, the surface roughness of aluminum specimens gradually increases, and the surface corrosion degree of aluminum specimens gradually deepens, corresponding to the aggravated ablation defects of buffer layers, which indicates that the surface roughness of aluminum specimens could be correlated with the ablation degree of buffer layers under the moisture conditions. Secondly, ultrasonic testing experiments are carried out on the ablated aluminum specimens, and the roughness of the corroded surfaces of aluminum specimens can be calculated from the amplitude ratio of adjacent ultrasonic echo signals. The calculated results show the same variation trend as the measured roughness in the experiment. The results in this study indicate that the ultrasonic tests could be used to detect the severity of buffer layer ablation defects, providing the research basis for the ultrasonic detection method of ablation defects in the buffer layer of high-voltage cables.

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Light Industry Machinery is the property of Light Industry Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Electric Power Engineering Technology is the property of Editorial Department of Electric Power Engineering Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bad lighting effect can be caused by bad pollution resistance of highway tunnel sidewall coating materials. Therefore, a kind of nano-silanion hydrophobic coating material is proposed, and its pollution resistance effect is examined and summarized from the aspects of principle analysis, test, and engineering application. The test results based on the pollution resistance principle show that the coating has the best pollution resistance effect when the content of nano-silica is 5% and the modifier content is 3%, while the coating smoothness reaches the highest when the coating color is white. The engineering application of this coating material in the Yakou tunnel of the Shanghai-Chongqing highway show that: (1) The reflection coefficients of the coating in different periods are generally maintained above 0.7, and the reflection coefficient decreases by approximately 3% after operation and cleaning, but the pollution resistance and lighting performance are still good. (2) Based on the comparative analysis of tunnel lighting parameters, MTPA, and sidewall cleaning cost before and after coating, it is verified that the application of the coating material can improve lighting safety and comfort, reduce operation and maintenance costs by 80% . [ABSTRACT FROM AUTHOR]

Steel pipe lining is a common support method for hydraulic engineering tunnels. It is very important to apply advanced technology to carry out void detection of steel pipe lining for project quality evaluation. In this paper, the longitudinal wave reflection coefficients of the three interfaces between steel and water, concrete and air were calculated, and the amplitude and phase variation characteristics of the reflection coefficients with the incident angle were analyzed. Through theoretical analysis, a data processing and analysis method by using the amplitude ratio of ultrasonic multiple reflection waves to detect voids was proposed. Concrete models with a thickness of 1.6 cm and 3.0 cm steel plates were made, and the models were tested with two types of 2.5 MHz probes. The results show that the reflected wave amplitude in the void area is relatively higher, which verifies the theoretical results of this paper. The pulse echo method is used for comparative detection, and the results show that the method has a certain detection effect. Since the actual impedance of the concrete cemented with the bottom of the steel plate is relatively lower, it is recommended to divide a larger detection unit for detection of a large amount of data to improve the accuraey of void discrimination.. [ABSTRACT FROM AUTHOR]

In view of the design difficulties of the vector impedance measurement module with a high dynamic range, this study designs a vector impedance measurement module based on the directional coupler using the directional coupler combined with the high-dynamic-range RF (Radio Frequency) logarithmic amplifier. The hardware and software design framework is given, the mathematical principle of the module is deduced, and the experimental verification and testing of the module are completed. The design makes full use of the characteristics of directional coupler, and the test system is small in size, good in scalability, fast in test speed and high in efficiency. The design can also be extended to a monitoring and measuring module, which can be used in communication equipment as an antenna monitoring component or power intensity control component of communication transmitter. After the verification, a number of practical applications have been developed using this design scheme. The high dynamic range of the proposed designed covers the application scenarios from 20~400 W, and obtains good application effect, which proves that the proposed design has good application, expansibility and high practical value. [ABSTRACT FROM AUTHOR]

A new type of breakwater structure, semi-elliptic breakwater, is proposed. The numerical wave flume is established by FLOW 3D, and the interaction between semi-elliptic breakwater and waves is simulated. The rationality of numerical model is proven by physical model test. Combined with numerical simulation results, the influence of wave parameters on hydrodynamic characteristics of semi-elliptic breakwater is analyzed. The results show that the reflection coefficient increases with increasing hs /H, the transmission coefficient decreases with increasing hs /H. Within the range of wave period, when D is constant, the wave retaining effect of semi-elliptical breakwater with larger wave period is better than that with smaller wave period. With the increase of D/b, the wave retaining effect becomes worse. The wave force increases with the decrease of hs /H and decreases with the increase of H/L. Under the same working condition, with the increase of a/b, the horizontal wave force on the structure decreases, the vertical wave force increases, and the dead weight of breakwater increases, so the stability of the breakwater is enhanced. The advantage of semi-elliptical breakwater is that the size relationship between horizontal axis and vertical axis can be designed according to different engineering conditions. If it is laid down with elliptical long axis, it is more suitable for weak foundation bed than semi-circular breakwater with the same depth, so as to be safer and more reliable. If it is erected with a short half axis, it can save materials compared with the half circular breakwater on the premise of preventing the same water depth, and thus reduce the construction cost. [ABSTRACT FROM AUTHOR]

The reflection characteristics of the terahertz channel are crucial for understanding and mastering the propagation mechanism of the terahertz channel, which are also required for a high-precision terahertz channel model for 6G.Therefore, the research status of terahertz channel reflection characteristics in theoretical modeling and measurement analysis were first summarized.Then, the reflection coefficient measurement campaign in the frequency range of 240 GHz to 310 GHz for five kinds of common building materials was conducted by a time-domain correlation-based terahertz channel measurement platform.It was found that the reflection coefficients were related to the incident angle.Based on the Rayleigh reflection coefficient theoretical model, a statistical reflection coefficient model was further proposed as a function of incident angle.Generally, the proposed model could accurately describe the variation law of the reflection coefficient with angle.Finally, research directions of terahertz channel reflection characteristics were discussed.

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal on Communication / Tongxin Xuebao is the property of Journal on Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In guided-wave based pipeline non-destructive inspection, it is inevitable that guided waves will interact with multiple defects, which makes damage identification more challenging. In this study, a numerical simulation was conducted to investigate the interaction of longitudinal guided waves with double notches in pipes. Firstly, a three-dimensional finite element model was established to simulate guided wave propagating in a pipe with a single notch. Then the established model was validated by comparing with existing experiments results. Based on the validated model, the guided wave reflection characteristics of two equal-sized notches of various relative positions were discussed systematically. The results show that, the relative circumferential positions of the two notches have little influence on the overall reflection, and the reflection coefficient rarely varies with the circumferential distance. However, the overall reflection of the two notches at the same circumferential location mainly depends on their axial positions, and the reflection coefficient varies periodically with the axial distance of the two notches. Moreover, the reflection coefficients of multiple notches within some axial range follow superposition principle approximately, which is very helpful for group corrosion detection.

The spectrum blueing technology for frequency-broadening based on spectrum inversion fully compresses the interference of wavelets under sparse constraints, broadens the low-frequency and high-frequency of seismic data, and uses colored terms of reflection coefficients in wells to improve the resolution of seismic data. Based on the reflection coefficient model and the single-trace convolution model test, the application basis of spectral blueing and the spectrum blueing technology for frequency-broadening based on spectrum inversion to improve the effect of thin-layer seismic response are analyzed. Results show that in reflection coefficient model test, the stratum thin layers and time correlation of reflection sequence jointly dominates the blue spectrum shape. In single-trace convolution model test, this method can significantly broaden the absolute frequency bandwidth of seismic data, and can highlight seismic response of thin layers and weak. The spectrum blueing technology for frequency-broadening based on spectrum inversion combines respective advantages of spectrum inversion and specrtrum blueing, introduces prior knowledge in wells to improve the descript ability of seismic data for thin layers or adjacent period sand bodies, and false interpretations seldom occur. The practical drilling shows that this method can improve the superposition relationship of sand bodies, and the correlation coefficient of on-well calibration is greatly improved compared with old data. [ABSTRACT FROM AUTHOR]

When there are micro-motion targets with large differences in the radar echo signals, the components of the weak reflection targets are often masked by the strong reflection targets and noise, which makes the weak reflection targets difficult to be detected. To solve the problem, a detection algorithm of large dynamic reflection coefficient micro-motion target is proposed. Firstly, the inverse Radon transform (IRT) algorithm is used to obtain the parameter estimation value of the strongest reflection components, and then the weak components are enhanced by removing the strong components one by one, which makes the weak components eater to be detected. This algorithm applies to detect micro-motion targets with different reflection coefficients and has high precision of parameter estimation. The simulation experiments show that the validity of the algorithm. At the same time, the performance of the algorithm is analyzed. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the physical model experiment, we put forward a new type of breakwater structure, and analyzed the attenuation properties of this new type breakwater from four aspects of the relative super high, wave steepness, relative wave height and opening rate. The results show that within the scope of the test, this new type breakwater has better wave attenuation effect in deep water and big wave steepness. When opening rate reached 16.75 %, wave attenuation effect of this breakwater is better than other opening situations. [ABSTRACT FROM AUTHOR]

On natural beaches nearly periodic shore-parallel sand ripples and sandbars can be often found in bays or on open coasts. When surface waves coming from the ocean propagate over patches of sand ripples and sandbars, once the Bragg condition is met, that is, the wavelength of surface waves is twice of the sandbar spacings, the Bragg resonant reflection may occur to cause a large portion of the incident wave energy to be reflected back to the ocean. Inspired by the Bragg resonant reflection phenomenon of natural sand ripples and sandbars, some pioneering scientists proposed the so-called Bragg submerged breakwater consisting of a series of small-size, low-height, shore-parallel artificial bars placed just outside the surf zone to shelter the coast and near-shore facilities from the attack of storm waves. A brief summary of the advances in research on Bragg resonance between ocean surface waves and natural sandbars as well as Bragg submerged breakwaters since 1980s was presented. [ABSTRACT FROM AUTHOR]

In order to decrease the reflection coefficient of underwater platform and promote its stealth performance, a method of covering a sound absorbing material on the platform is proposed. The transfer matrix method is used to calculate the reflection and transmission coefficients of composite structure in underwater platform in the case of oblique incidence of sound waves. The influences of the arranging sequence and parameters of sound absorbing materials on the acoustic characteristics of underwater platform are analyzed. The results show that the reflection coefficient of platform without sound absorbing material is close to 1; the constant reflection coefficient curve of the platform with sound absorbing material is a hyperbolic curve as the functions of incident angle and frequency, and its reflection coefficient obviously descreases at high frequency. This shows the frequency selectivity in the absorbing performance of platform, and the absorption wave band of platform transfers to lower frequencies by increasing the thickness of sound absorbing material. When the loss coefficient of material raises, the reflection coefficient of platform goes down. The experimental results coincides well with the theoretically calculated results. [ABSTRACT FROM AUTHOR]

In an enclosure room, the speech signal captured by a distant microphone is usually contaminated by reverberation, in which the late reverberation severely degrades the speech intelligibility. Common denoising methods can only remove the additive noise such as white noise, not the reverberation which is the convolution of clean speech and room impulse response. Therefore, dereverberation algorithm should be applied to eliminate the bad effects caused by late reverberations. In this paper, we propose an improved dereverberation algorithm using multiple-step linear prediction. This method modifies the process of pre-whitening, which can raise the first two formants of the speech signal. Experimental results showed that new dereverberation algorithm can remove most of the late reverberations and reserve more low frequency components of clean speech, consequently improve the speech intelligibility. [ABSTRACT FROM AUTHOR]

The reflection coefficient is one of the most important acoustic parameters of materials. In order to measure it in water tank, a method based on pulse compression technique was proposed to extract the directive and reflective waves from the received compressing signal. This method can overcome unavoidable multi-path disturbance in experiments and easily obtain the reflection coefficient at different frequencies in the measured frequency band. That is, the wide-band measurement for reflection coefficient was realized. The method was verified through simulation. Further more, the experiment results in water tank for an aluminum plate in the frequency range of 30 - 40 kHz were given also. Comparison of experimental results with theoretical value shows that, although the experiment curve exhibits some deviation and fluctuation, a more accurate result would be obtained by increasing the frequency band of transmitting signal to improve the compression effect or applying appropriate window functions to suppress the level of side lobes. [ABSTRACT FROM AUTHOR]

A method of discontinuity modeling with high-ordered parameters is developed based on the wave-propagation characteristics. The characteristic values are firstly derived from the discontinuity reflection curve and then these values are used to identify the parameters of discontinuity by the analytical relations among the parameters and the reflection coefficients. Numerical examples, which comprise of a finite uniform beam, with the one-order and two-order discontinuities being simulated by a set of steel blocks and springs, are set up. The theoretical results are then compared with those from experiments. It shows that the errors of the identified mass, translational stiffness and moment of inertia are below 8%, 4% and 4%, respectively. The possible reasons, which lead to these identification errors, are discussed. [ABSTRACT FROM AUTHOR]

Taking hydroponically cultured arrow-leaf saltbush (Atriplex triangularis) seedlings as test materials, and using electrical conductivity detector, atomic spectroscopy, and pressure bomb, this paper studied the effects of salt stress on the seedlings root membrane permeability, ion uptake, and reflection coefficient, and analyzed the salt-resistance characteristics and related mechanisms of A. triangularis. The results showed that with increasing salt stress, the root membrane permeability increased, but the reflection coefficient decreased. Salt stress decreased the total K+ uptake and increased the total Na+ uptake, but the relative amount of absorbed K+ increased while that of absorbed Na+ decreased. Under salt stress, A. triangularis roots had a higher regulation capability in their ion uptake, and the reduction of root reflection coefficient was favourable to the water absorption by the roots with moderate negative pressure, and accordingly, reduced the danger of xylem cavitation. All these features could be closely related to the higher salt-resistance of A. triangularis. [ABSTRACT FROM AUTHOR]

The sound baffle is a useful component for the sonar design. According to the different requirement, it's the keyboard to optimize the physical and structural parameters of the baffle. A Genetic algorithm, as an efficient optimization method, is used widely in the engineering optimization. However, the composition of chromosome, the coding form and the definition of cost function would seriously influence the performance of genetic algorithm because its calculation doesn't depend on the external information. According to the aim at maintain the reflection coefficients minimized and uniformed in the scopes of both definite incident frequencies and angles, the optimization method of parameters of layered composite sound baffle based on the genetic algorithm will be presented. In this algorithm, the chromosome coding based on transfer matrix and the cost function based on the statistic principle are proposed. The dependability and validity of the algorithm are proved and the influence led by changing the cost function on the result from the optimum algorithm is analyzed with the simulation calculation. [ABSTRACT FROM AUTHOR]