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المؤلفون: Cichoń, Krzysztof, Nikiforuk, Maciej, Kliks, Adrian
المصدر: Sensors. 24(10)
مصطلحات موضوعية: foliage attenuation, millimeter-wave propagation, radiative transfer equation, vegetation attenuation, Signalbehandling, Signal Processing
الوصف: As fixed wireless access (FWA) is still envisioned as a reasonable way to achieve communications links, foliage attenuation becomes an important wireless channel impairment in the millimeter-wave bandwidth. Foliage is modeled in the radiative transfer equation as a medium of random scatterers. However, other phenomena in the wireless channel may also occur. In this work, vegetation attenuation measurements are presented for a single tree alley for 26–32 GHz. The results show that vegetation loss increases significantly after the second tree in the alley. Measurement-based foliage losses are compared with model-based, and new tuning parameters are proposed for models.
وصف الملف: electronic
الوصول الحر: https://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-105853Test
https://doi.org/10.3390/s24103190Test
https://ltu.diva-portal.org/smash/get/diva2:1866494/FULLTEXT01.pdfTest -
2دورية أكاديمية
المؤلفون: Wang, Jonathan, Wu, Kesheng, Sim, Alex, Hwangbo, Seongwook
المصدر: Sensors. 23(4)
مصطلحات موضوعية: partial discharges, source location, UHF measurements, time of arrival estimation, waveform analysis, FDTD methods, nonlinear wave propagation, Analytical Chemistry, Environmental Science and Management, Ecology, Distributed Computing, Electrical and Electronic Engineering
الوصف: The most common source of transformer failure is in the insulation, and the most prevalent warning signal for insulation weakness is partial discharge (PD). Locating the positions of these partial discharges would help repair the transformer to prevent failures. This work investigates algorithms that could be deployed to locate the position of a PD event using data from ultra-high frequency (UHF) sensors inside the transformer. These algorithms typically proceed in two steps: first determining the signal arrival time, and then locating the position based on time differences. This paper reviews available methods for each task and then propose new algorithms: a convolutional iterative filter with thresholding (CIFT) to determine the signal arrival time and a reference table of travel times to resolve the source location. The effectiveness of these algorithms are tested with a set of laboratory-triggered PD events and two sets of simulated PD events inside transformers in production use. Tests show the new approach provides more accurate locations than the best-known data analysis algorithms, and the difference is particularly large, 3.7X, when the signal sources are far from sensors.
الوصول الحر: https://escholarship.org/uc/item/2k81z2xxTest
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3دورية أكاديمية
المؤلفون: Krzysztof Cichoń, Maciej Nikiforuk, Adrian Kliks
المصدر: Sensors, Vol 24, Iss 10, p 3190 (2024)
مصطلحات موضوعية: foliage attenuation, millimeter-wave propagation, vegetation attenuation, radiative transfer equation, Chemical technology, TP1-1185
الوصف: As fixed wireless access (FWA) is still envisioned as a reasonable way to achieve communications links, foliage attenuation becomes an important wireless channel impairment in the millimeter-wave bandwidth. Foliage is modeled in the radiative transfer equation as a medium of random scatterers. However, other phenomena in the wireless channel may also occur. In this work, vegetation attenuation measurements are presented for a single tree alley for 26–32 GHz. The results show that vegetation loss increases significantly after the second tree in the alley. Measurement-based foliage losses are compared with model-based, and new tuning parameters are proposed for models.
وصف الملف: electronic resource
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4دورية أكاديمية
المؤلفون: Hubbard, Peter G, Vantassel, Joseph P, Cox, Brady R, Rector, James W, Yust, Michael BS, Soga, Kenichi
المصدر: Sensors. 22(12)
مصطلحات موضوعية: Engineering, Electrical Engineering, Electronics, Sensors and Digital Hardware, Bioengineering, DAS, geophones, transfer function, wave propagation, strain measurement, DFOS, Analytical Chemistry, Environmental Science and Management, Ecology, Distributed Computing, Electrical and Electronic Engineering, Electrical engineering, Electronics, sensors and digital hardware, Environmental management, Distributed computing and systems software
الوصف: Quantitative dynamic strain measurements of the ground would be useful for engineering scale problems such as monitoring for natural hazards, soil-structure interaction studies, and non-invasive site investigation using full waveform inversion (FWI). Distributed acoustic sensing (DAS), a promising technology for these purposes, needs to be better understood in terms of its directional sensitivity, spatial position, and amplitude for application to engineering-scale problems. This study investigates whether the physical measurements made using DAS are consistent with the theoretical transfer function, reception patterns, and experimental measurements of ground strain made by geophones. Results show that DAS and geophone measurements are consistent in both phase and amplitude for broadband (10 s of Hz), high amplitude (10 s of microstrain), and complex wavefields originating from different positions around the array when: (1) the DAS channels and geophone locations are properly aligned, (2) the DAS cable provides good deformation coupling to the internal optical fiber, (3) the cable is coupled to the ground through direct burial and compaction, and (4) laser frequency drift is mitigated in the DAS measurements. The transfer function of DAS arrays is presented considering the gauge length, pulse shape, and cable design. The theoretical relationship between DAS-measured and pointwise strain for vertical and horizontal active sources is introduced using 3D elastic finite-difference simulations. The implications of using DAS strain measurements are discussed including directionality and magnitude differences between the actual and DAS-measured strain fields. Estimating measurement quality based on the wavelength-to-gauge length ratio for field data is demonstrated. A method for spatially aligning the DAS channels with the geophone locations at tolerances less than the spatial resolution of a DAS system is proposed.
وصف الملف: application/pdf
الوصول الحر: https://escholarship.org/uc/item/1vr4134zTest
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5دورية أكاديمية
المؤلفون: Vassily Mikhaltsevitch, Maxim Lebedev
المصدر: Sensors, Vol 24, Iss 4, p 1122 (2024)
مصطلحات موضوعية: strain gauges, elastic properties, wave propagation, seismic frequency, Chemical technology, TP1-1185
الوصف: Numerous experimental and theoretical studies undertaken to determine the effective stress coefficient for seismic velocities in rocks stem from the importance of this geomechanical parameter both for monitoring changes in rock saturation and pore pressure distribution in connection with reservoir production, and for overpressure prediction in reservoirs and formations from seismic data. The present work pursues a task to determine, in the framework of a low-frequency laboratory study, the dependence of the elastic moduli of n-decane-saturated sandstone on the relationship between pore and confining pressures. The study was conducted on a sandstone sample with high quartz and notable clay content in a quasi-static regime when a 100 mL tank filled with n-decane was directly connected to the pore space of the sample. The measurements were carried out at a seismic frequency of 2 Hz and strains, controlled by semiconductor strain gauges, not exceeding 10−6. The study was performed using a forced-oscillation laboratory apparatus utilizing the stress–strain relationship. The dynamic elastic moduli were measured in two sets of experiments: at constant pore pressures of 0, 1, and 5 MPa and differential pressure (defined as a difference between confining and pore pressures) that varied from 3 to 19 MPa; and at a constant confining pressure of 20 MPa and pore pressure that varied from 1 to 17 MP. It was shown that the elastic moduli obtained in the measurements were in good agreement with the Gassmann moduli calculated for the range of differential pressures used in our experiments, which corresponds to the effective stress coefficient equal to unity.
وصف الملف: electronic resource
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6دورية أكاديمية
المصدر: Sensors, Vol 24, Iss 1, p 282 (2024)
مصطلحات موضوعية: R(anging) -mode, ground wave propagation, radionavigation, Chemical technology, TP1-1185
الوصف: Time delays caused by ground wave propagation are the primary source of systematic error limiting the performance of the medium-frequency R-Mode radionavigation system. To achieve the desired ranging accuracy and compensate these delays, we have conceived a comprehensive correction scheme based on the prediction and application of the Atmospheric and Ground wave Delay Factor (AGDF). The AGDF was computed and mapped in 2D for a number of MF R-Mode transmitters in the Baltic Sea that were embedded into the receiver and evaluated during a large-scale measurement campaign. Our results show that the proposed AGDF approach is valid for the MF R-Mode system and provides accurate corrections of ground wave propagation delays within the performance requirements.
وصف الملف: electronic resource
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7دورية أكاديمية
المؤلفون: Cheng Zhang, Zhijin Qiu, Chen Fan, Guoqing Song, Bo Wang, Tong Hu, Jing Zou, Zhiqian Li, Sheng Wu
المصدر: Sensors, Vol 23, Iss 21, p 8786 (2023)
مصطلحات موضوعية: electromagnetic wave propagation, evaporation duct, multimodel fusion, Monin–Obukhov similarity theory, LIBSVM, Chemical technology, TP1-1185
الوصف: Evaporation ducts are abnormal states of the atmosphere in the air–sea boundary layer that directly affect the propagation trajectory of electromagnetic (EM) waves. Therefore, an accurate diagnosis of the evaporation duct height (EDH) is important for studying the propagation trajectory of EM waves in evaporation ducts. Most evaporation duct models (EDMs) based on the Monin–Obukhov similarity theory are empirical methods. Different EDMs have different levels of environmental adaptability. Evaporation duct diagnosis methods based on machine learning methods only consider the mathematical relationship between data and do not explore the physical mechanism of evaporation ducts. To solve the above problems, this study observed the meteorological and hydrological parameters of the five layers of the low-altitude atmosphere in the East China Sea on board the research vessel Xiangyanghong 18 in April 2021 and obtained the atmospheric refractivity profile. An evaporation duct multimodel fusion diagnosis method (MMF) based on a library for support vector machines (LIBSVM) is proposed. First, based on the observed meteorological and hydrological data, the differences between the EDH diagnosis results of different EDMs and MMF were analyzed. When ASTD ≥ 0, the average errors of the diagnostic results of BYC, NPS, NWA, NRL, LKB, and MMF are 2.57 m, 2.92 m, 2.67 m, 3.27 m, 2.57 m, and 0.24 m, respectively. When ASTD < 0, the average errors are 2.95 m, 2.94 m, 2.98 m, 2.99 m, 2.97 m, and 0.41 m, respectively. Then, the EM wave path loss accuracy analysis was performed on the EDH diagnosis results of the NPS model and the MMF. When ASTD ≥ 0, the average path loss errors of the NPS model and MMF are 5.44 dB and 2.74 dB, respectively. When ASTD < 0, the average errors are 5.21 dB and 3.46 dB, respectively. The results show that the MMF is suitable for EDH diagnosis, and the diagnosis accuracy is higher than other models.
وصف الملف: electronic resource
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8دورية أكاديمية
المؤلفون: Krzysztof Bronk, Patryk Koncicki, Adam Lipka, Rafał Niski, Błażej Wereszko
المصدر: Sensors, Vol 23, Iss 17, p 7593 (2023)
مصطلحات موضوعية: wind farms, radio wave propagation, radio channel, marine radiocommunication, VHF band, signal interference, Chemical technology, TP1-1185
الوصف: This article discusses several aspects related to the modeling of the radio channel in the wind farm propagation environment. The first part of the article is filled with the analysis of the ITU-R BT.1893-1 model, which—as will be shown—is also applicable to systems operating in the VHF and UHF bands. The conducted measurement campaign makes it possible to model a radio channel for VHF operating systems in the wind farm propagation environment. Thanks to the obtained results, the authors propose the VHF radio channel model for that environment. Using the software implementation of this model, the authors carry out a detailed simulation analysis of the impact of wind turbines on radio systems operating in the VHF band. The main motivation for this work is the growing importance of the offshore wind energy in general, numerous investments in that area in Poland, and the lack of existing mathematical models regarding the wind farms’ impact on the VHF systems. The VHF band is of special interest here, as this part of the spectrum is utilized by numerous marine administration and border protection radio systems, which can be adversely affected by the wind turbines (due to interference and/or radio shadowing).
وصف الملف: electronic resource
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9دورية أكاديمية
المؤلفون: Fernando Sánchez Iglesias, Antonio Fernández López
المصدر: Sensors, Vol 23, Iss 16, p 7220 (2023)
مصطلحات موضوعية: SHM, wave propagation, composites, ray tracing, Chemical technology, TP1-1185
الوصف: This study presents a novel method based on ray tracing for analyzing wave propagation in composites specifically tailored for structural health monitoring applications. This method offers distinct advantages over the commonly used finite element method mainly in computational resource utilization, which has become a limiting factor for these kinds of analyses. The ray tracing method is evaluated against a number of example cases representing structural details such as thickness changes, stringers, or simulated damage, and the significance of ray tracing to study wave propagation under these conditions and how it can serve as a valuable tool for structural health monitoring are highlighted. This model has been developed as part of a complete SHM framework with the intention of being an efficient and simple way to calculate wave propagation and therefore it could be used as a way to determine relevant damage indicators or train an artificial intelligence model.
وصف الملف: electronic resource
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10دورية أكاديمية
المؤلفون: David W. Greve, Jagannath Devkota, Paul R. Ohodnicki, Ruishu Wright
المصدر: Sensors, Vol 23, Iss 11, p 4991 (2023)
مصطلحات موضوعية: Goubau, surface acoustic wave, sensing, launcher, wave propagation, Chemical technology, TP1-1185
الوصف: We examine the application of guided waves on a single conductor (Goubau waves) for sensing. In particular, the use of such waves to remotely interrogate surface acoustic wave (SAW) sensors mounted on large-radius conductors (pipes) is considered. Experimental results using a small-radius (0.0032 m) conductor at 435 MHz are reported. The applicability of published theory to conductors of large radius is examined. Finite element simulations are then used to study the propagation and launching of Goubau waves on steel conductors up to 0.254 m in radius. Simulations show that waves can be launched and received, although energy loss into radiating waves is a problem with current launcher designs.
وصف الملف: electronic resource
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