المؤلفون: Wang, Ping, Li, Xinju, Min, Xiangyu, Xu, Shuo, Zhao, Guangming, Fan, Deqiang

المصدر: Near Surface Geophysics; Jun2024, Vol. 22 Issue 3, p339-357, 19p

مصطلحات موضوعية: GROUND penetrating radar, SOIL moisture, PLATEAUS, ELECTROMAGNETIC wave propagation, SOIL profiles, SOILS, LAND cover

مصطلحات جغرافية: CHINA

مستخلص: Soil layers affect the vertical movement of moisture and salt, eventually resulting in land cover and land use pattern changes. This study explored the ability of ground penetrating radar (GPR) to detect soil layers in the modern Yellow River Delta of China and assessed its accuracy. It was found that soil moisture and salt had a strong dampening effect on the electromagnetic wave signal which resulted in blurred GPR images of the soil profile below 1 m. The cultivated soil layers of different crop types, such as rice, wheat, corn and cotton, were accurately identified in GPR images. To estimate an individual soil layer thickness, the propagation velocity of the electromagnetic wave was calculated using soil mass moisture content, and the propagation time was confirmed by comparing the GPR image with the amplitude–time plot of the soil profile. The estimated thickness was 1.02 times the thickness determined in the field and the average estimation error was 0.04 m, which was 24.09% of the soil layer thickness determined in the field. The second derivative value of envelope amplitude energy with time (SDEA) was used to describe the amplitude change in the soil layers. The SDEA has negative logarithmic and power function relationships with soil mass moisture content and electrical conductivity, respectively. The present results provide a reference database for future quantitative soil investigation in the sedimentary plain area using GPR. [ABSTRACT FROM AUTHOR]

: Copyright of Near Surface Geophysics is the property of Wiley-Blackwell 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.)

المؤلفون: Wang, Qing, Bi, Chenguang, Zhang, Jiawei, Wang, Haige, Guan, Zhichuan

المصدر: Processes; May2023, Vol. 11 Issue 5, p1525, 18p

مصطلحات موضوعية: DRILL stem, ACOUSTIC wave propagation, SOUND-wave attenuation, THEORY of wave motion, ACOUSTIC excitation, TRANSMISSION of sound

مستخلص: Aiming at the problem of the unclear sound wave attenuation in the signal transmission of the load-bearing drill string, an experimental device for the sound wave propagation characteristics in the curved drill string was set up. The influence of the drill string structure and acoustic excitation parameters on the sound propagation characteristics in the drill string under different loads is different. The results show that the curvature of the drill string has an influence on the propagation of the sound wave in the drill string, and its rule is related to the curvature of the drill string and the frequency of the sound wave. The pulse repetition rate, excitation voltage, and pulse width only affect the passband amplitude, and the effect is significantly greater than the curvature of the drill string. The main influencing factor of its sound transmission characteristics is the degree of drill string curvature. The low-frequency signal should be preferentially selected as the carrier of downhole information transmission after considering the influence of drill string bending on acoustic transmission. [ABSTRACT FROM AUTHOR]

: Copyright of Processes is the property of MDPI 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.)

المؤلفون: Yuan, Zhaojie, Gao, Guofu, Wang, Yi, Fu, Zongxia, Xiang, Daohui

المصدر: International Journal of Advanced Manufacturing Technology; Jul2022, Vol. 121 Issue 5/6, p4187-4208, 22p

مصطلحات موضوعية: ULTRASONIC cutting, HARD materials, ACOUSTIC wave propagation, BRITTLE materials, ULTRASONIC propagation, ALLOYS, CUTTING (Materials)

مستخلص: In order to solve the problems of poor machining accuracy and surface quality of hard and brittle materials such as Ti2AlNb intermetallic alloy in conventional machining, the principle of apparent elasticity method was used to design a flat-plate vibration device. Firstly, the propagation characteristics of ultrasonic in inclined slot plate were analyzed by using the propagation law of acoustic wave in different media. Secondly, the vibration characteristics were analyzed and discussed in detail by using finite element software. Finally, the influence of the vibration characteristics of vibration platform on the cutting performance of Ti2AlNb alloy was studied through ultrasonic vibration cutting and common cutting (CC) experiments. The finite element modelling (FEM) and test results showed that when the slot width was 2 mm and the inclination angle was 45°, the vibration effect of the plate vibration device was the best, and the vertical upward vibration component was generated at the workpiece installation area of the plate. The errors between the measured frequency and the results of theoretical calculation and finite element analysis were 1.78% and 0.36%, respectively, which showed the reliability of finite element simulation. Compared with the three-dimensional ultrasonic vibration cutting (3DUVC) and CC, the results of two-dimensional ultrasonic vibration cutting (2DUVC) based on flat-plate vibration device showed an obvious "drainage tank" microstructure in variable speed cutting; when the rotating speed was 1700 r/min, the roughness value of 2DUVC was 54% and 57% lower than that of 3DUVC and CC, respectively. The amplitude along the feed direction was 8 μm, the surface roughness of 2DUVC decreased by 64% and 65.9%, respectively, compared with 3DUVC and CC. The number of chip sawtooth increased with the increase of ultrasonic amplitude and vibration dimension. The experimental results showed that for Ti2AlNb alloy, ultrasonic vibration cutting can obtain higher surface quality, and the two-dimensional ultrasonic vibration platform was helpful to improve the cutting performance of materials, and the 3DUVC can realize the rapid removal of materials. [ABSTRACT FROM AUTHOR]

: Copyright of International Journal of Advanced Manufacturing Technology is the property of Springer Nature 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.)

المؤلفون: Zheng, Jingjing, Zhang, Xueqian¹ alearn1988@tju.edu.cn, Liu, Lixiang², Li, Quan³, Singh, Leena⁴, Han, Jiaguang¹, Yan, Fengping⁵, Zhang, Weili

المصدر: Journal of Infrared, Millimeter & Terahertz Waves. Sep2017, Vol. 38 Issue 9, p1034-1046. 13p.

مصطلحات موضوعية: *SUBMILLIMETER wave propagation, *ELECTROMAGNETIC spectrum, *WAVEFRONTS (Optics), *ELECTROMAGNETIC surface waves, *PHOTOCHEMISTRY

مستخلص: Metasurfaces have been very successful at demonstrating the ability to control the wave propagation over the broad electromagnetic spectrum in recent years. The output wavefronts can be controlled at will, by encoding specially designed abrupt changes of electromagnetic parameters into the metasurfaces, such as phase and amplitude. Constituted by a single- or few-layer of planar structures, metasurfaces are straightforward in design and fabrication, thus promising many credible applications. Moreover, such control concept can be further extended to the surface wave regime. In this review, we present our recent progress on metasurfaces capable of tailoring the propagation of both free-space and surface terahertz waves. Following an introduction of the basic concept and theory, a number of unique terahertz metasurfaces are presented, showing the ability to device ultra-thin and compact functional terahertz components. [ABSTRACT FROM AUTHOR]

المؤلفون: Hood, A. W., Brooks, S. J., Wright, A. N.

المصدر: Proceedings: Mathematical, Physical and Engineering Sciences, 2002 Oct 01. 458(2026), 2307-2325.

الوصول الحر: https://www.jstor.org/stable/3067317Test

المؤلفون: Lewicki, Pawel, Burridge, Robert, de Hoop, Maarten V.

المصدر: SIAM Journal on Applied Mathematics, 1996 Feb 01. 56(1), 256-276.

الوصول الحر: https://www.jstor.org/stable/2102531Test

المؤلفون: Imberger, Jörg, Antenucci, Jason P.

المصدر: Limnology and Oceanography, 2006 Jan 01. 51(1), 229-246.

الوصول الحر: https://www.jstor.org/stable/4499577Test

المؤلفون: Lei Zhang, Yuan Gao, Shang Gao, Tie Jun Cui, Cong Xiao, Qiang Cheng, Shi Jin, Jing Cheng Liang

المصدر: IEEE Transactions on Antennas and Propagation. 70:8798-8808

مصطلحات موضوعية: Physics, Amplitude, business.industry, Acoustics, Reciprocity (electromagnetism), Phase (waves), Wireless, Decoupling (cosmology), Sensitivity (control systems), Electrical and Electronic Engineering, business, Interference (wave propagation), Electromagnetic radiation

الوصف: Recently, reconfigurable intelligent surface (RIS) has attracted continuous attention in wireless communications. Because the normal incidence condition of electromagnetic waves cannot always be satisfied in practical applications, the angular insensitivity in RISs has become an important issue. The angular sensitivity in RISs may lead to the failure of RIS-assisted wireless communication networks that rely on the reciprocity of wireless channels. In this work, an angle-insensitive 3-bit RIS meta-atom is proposed. By introducing metallic vias in the substrate of programmable meta-atoms, the interference induced by multiple reflections in the multilayered structure is restrained, and the decoupling between adjacent meta-atoms makes the metasurface insensitive to the incident angle. Hence the angular insensitivity can be achieved. An RIS is fabricated using the proposed angleinsensitive programmable meta-atom with metallic vias, which is capable of maintaining stable phase and amplitude responses at oblique incidences. Both simulated and measured results show stable angle performance. A maximum of 3150 phase range and eight digital coding states with 450 stable interval are obtained for wide incidence angles from 00 to 600. Finally, numerical simulations and experimental results of anomalous reflections are performed to verify the angular reciprocity of the proposed RIS, which is important in wireless communications.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::5df11ba3671da730500434986cf26361Test
https://doi.org/10.1109/tap.2021.3130108Test

المؤلفون: Brearley, Maurice N.

المصدر: The Mathematical Gazette, 2005 Nov 01. 89(516), 437-440.

الوصول الحر: https://www.jstor.org/stable/3621935Test

المؤلفون: Titov, Vasily, Rabinovich, Alexander B., Mofjeld, Harold O., Thomson, Richard E., González, Frank I.

المصدر: Science, 2005 Sep . 309(5743), 2045-2048.

الوصول الحر: https://www.jstor.org/stable/3843664Test