المؤلفون: Benidir, Adel, Debbakh, Said, Chaibeddra, Siham

المصدر: Selected Scientific Papers: Journal of Civil Engineering; Dec2023, Vol. 18 Issue 1, p1-15, 15p

مصطلحات موضوعية: COMPRESSIVE strength, ULTRASONIC testing, REINFORCED concrete, ELASTIC wave propagation, NONDESTRUCTIVE testing, ELASTIC waves

مستخلص: This paper studies the influence of core diameters and slenderness ratio on the assessment of the actual compressive strength of concrete on reinforced-concrete elements. The experiment consists of the preparation of three reinforced concrete columns and the extraction of cores to carry out both destructive (core diameter of 64 mm, 79 mm, and 103 mm) and non-destructive tests. The non-destructive test deals with the propagation of elastic and compressive waves by deriving the ultrasound pulse velocities. The results show that the assessment of the compressive strength of concrete depends strongly on the diameter of cores and the extraction zones. Furthermore, the derivation of the actual compressive strength by referring to the compressive strengths of the cores with a diameter of 64 mm shows a stringent appearance of a size effect. More interestingly, valuable details about the correlation between the concrete compressive strength assessment based on destructive and non-destructive tests are also presented. [ABSTRACT FROM AUTHOR]

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المؤلفون: Kliuchka, Anatolii, Harťanský, René, Halgoš, Ján

المصدر: Journal of Electrical Engineering; Oct2023, Vol. 74 Issue 5, p422-433, 12p

مصطلحات موضوعية: COMPUTATIONAL electromagnetics, INTERNET of things, RADIO wave propagation, ELECTROMAGNETIC fields, COMPUTER simulation

مستخلص: The paper investigates software solutions to simulate radio waves propagation in urban environment, specifically for the context of the Internet of Things (IoT). The purpose of the study is to provide a comprehensive guide for utilizing the Altair Feko software to obtain a detailed representation of the IoT network, its associated parameters and how they relate to the modeling of electromagnetic fields. It is beneficial to simulate the network during the design stage to obtain valuable data and make necessary adjustments. The key features of a Sigfox or other low power IoT network can be obtained by simulation, enabling an evaluation of the network design prior to its actual implementation. Given the growing demand for IoT devices and networks, researching the optimal design and performance of such networks is of great importance. This underscores the need for continuous exploration of effective methods to achieve efficient design and performance of IoT networks. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Electrical Engineering is the property of Sciendo 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: Wu Chenguang, Shao Qi, Li Gongming, Liu Shanfeng, Gao Yang, Zhang Qizhen

المصدر: Applied Mathematics and Nonlinear Sciences, Vol 9, Iss 1 (2024)

مصطلحات موضوعية: traveling wave propagation, fault localization, split-phase current phase, transient current fluctuation, distributed detection, 68t05, Mathematics, QA1-939

الوصف: Transmission lines are the arteries of power system operation, carrying the important task of conveying electric energy, which is the most fragile and fault-prone place in the power system. This paper first analyzes the traveling wave propagation characteristics of transmission lines. It builds a mathematical model for the refraction and reflection phenomena of traveling waves that occur in the process of readjustment and distribution of transmission lines. The three traveling wave monitoring points nearest to the fault point are used to localize the fault, and the principle of the phase difference of split-phase current is explored based on the fault component. By means of experimental analysis, the phase currents of the three measurement points are detected, and for the transient current waveforms at the time of lightning strikes and short-circuits, the lightning fault localization method of the transmission line based on wavelet transforms is proposed and analyzed for fault localization of the technique. The results of simulation experiments show that when a ground fault occurs in the L1 phase of the line, the current fault components of measurement point 2 and measurement point 3 increase rapidly, and the element between measurement points is more than 10kA. The phase difference of the components is 180°, so the fault interval of the transmission line is from measurement point 2 to measurement point 3, and the fault phase is the L1 phase. Upon analysis, it is apparent that the actual fault distance error of 0.838km is the measurement of the fault distance of the transmission line, and the method proposed in this paper has a high level of measurement accuracy.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/2444-8656Test

الوصول الحر: https://doaj.org/article/ad55d93a37eb4f628a4791842c5db50eTest

المؤلفون: Kowalczyk Piotr

المصدر: Studia Geotechnica et Mechanica, Vol 44, Iss 4, Pp 253-266 (2022)

مصطلحات موضوعية: finite element modelling, earthquake engineering, wave propagation, soil dynamics, soil nonlinearity, Engineering geology. Rock mechanics. Soil mechanics. Underground construction, TA703-712

الوصف: High-frequency motion is often observed in small-scale experimental works carried out in flexible containers under simplified seismic loading conditions when single harmonic sine input motions are introduced at the base of a soil specimen. The source of the high-frequency motion has often been sought in experimental inaccuracies. On the other hand, the most recent numerical studies suggested that high-frequency motion in the steady-state dynamic response of soil subjected to harmonic excitation can also be generated as a result of soil elastic waves released in non-linear hysteretic soil upon unloading. This work presents an example of a finite element numerical study on seismic soil–structure interaction representative of an experimental setup from the past. The results show how high-frequency motion generated in soil in the steady-state response, apparently representative of soil elastic waves, affects the steady-state response of a structure, that is, it is presented how the structure in the analysed case resonates with the soil elastic waves. The numerical findings are verified against the benchmark experimental example to indicate similar patterns in the dynamic response of the structure.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/2083-831XTest

الوصول الحر: https://doaj.org/article/5ac20514a773462a9ae92293cdc22c55Test

المؤلفون: Kamel Filali, Badreddine Sbartai

المصدر: Studia Geotechnica et Mechanica, Vol 44, Iss 2, Pp 162-174 (2022)

مصطلحات موضوعية: earthquakes, probabilistic hazard analysis, site effects/liquefaction, probability, random variable, wave propagation, Engineering geology. Rock mechanics. Soil mechanics. Underground construction, TA703-712

الوصف: The Youd etal liquefaction resistance curves developed in 2001 to characterize the cyclic resistance of soil based on SPT test are the most used in the context of the Seed and Idriss simplified procedure as a deterministic model. These curves were developed from a modified database of Seed etal. in 1985 with the assumption that the actual peak shear stress (τd) induced at depth h is always less than that predicted by the simplified procedure (τr) of Seed and Idriss (rd= τd/τr1). As in this case, the assumption of the simplified procedure is not verified, Filali and Sbartai have proposed a corrector factor (RC) in the range where rd>1 to adjust the deformable and rigid body. In this paper, we will present a probabilistic study for the evaluation of the liquefaction potential using a database based on SPT measurement compiled after the Chi-Chi Taiwan earthquake, in which the cyclic stress ratio is evaluated using the proposed corrector factor. The objective of this study is to present a probabilistic shape of the cyclic resistance ratio (CRR) curves based on the original simplified method of Seed and Idriss and the corrected version and a new formulation for computing the probability of liquefaction.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/2083-831XTest

الوصول الحر: https://doaj.org/article/d7761a1df62e45cd8434044e78677f13Test

المؤلفون: Kozaczka, Eugeniusz¹, Grelowska, Grażyna²

المصدر: Polish Maritime Research. Jun2017, Vol. 24 Issue 2, p48-55. 8p.

مصطلحات موضوعية: *ACOUSTIC wave propagation, *WATER depth, *OCEAN waves, *STOCHASTIC processes, *SOUND pressure

مستخلص: The work is devoted to the propagation of low frequency waves in a shallow sea. As a source of acoustic waves, underwater disturbances generated by ships were adopted. A specific feature of the propagation of acoustic waves in shallow water is the proximity of boundaries of the limiting media characterised by different impedance properties, which affects the acoustic field coming from a source situated in the water layer 'deformed' by different phenomena. The acoustic field distribution in the real shallow sea is affected not only by multiple reflections, but also by stochastic changes in the free surface shape, and statistical changes in the seabed shape and impedance. The paper discusses fundamental problems of modal sound propagation in the water layer over different types of bottom sediments. The basic task in this case was to determine the acoustic pressure level as a function of distance and depth. The results of the conducted investigation can be useful in indirect determination of the type of bottom. [ABSTRACT FROM AUTHOR]

المؤلفون: Fiala, Pavel, Bartušek, Karel, Dědková, Jarmila, Kadlec, Radim, Dohnal, Přemysl

المصدر: Measurement Science Review; Aug2019, Vol. 19 Issue 4, p144-152, 9p

مصطلحات موضوعية: ELECTROMAGNETIC waves, COMPUTATIONAL electromagnetics, ELECTROMAGNETIC spectrum, GAMMA rays, ELECTROMAGNETIC wave propagation

مستخلص: We discuss and compare the results obtained from experimental measurements of a two-layer, Ni and TiO2 nanometric structure deposited on siliceous glass. Utilizing previous theoretical models of multilayers or periodic systems and their verifications, the paper focuses on measurement in the NIR, visible, UV, X-ray, and gamma bands of the electromagnetic spectrum; the wavelength of the incident electromagnetic wave is respected. The proposed evaluation comprises a brief description of a Snell's law-based semi-analytic model of electromagnetic wave propagation through a layered material. We also demonstrate the expected anti-reflective and shielding effects in the X-ray and gamma-ray bands, respectively. [ABSTRACT FROM AUTHOR]

: Copyright of Measurement Science Review is the property of Sciendo 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: Herbut Aneta

المصدر: Studia Geotechnica et Mechanica, Vol 39, Iss 1, Pp 3-12 (2017)

مصطلحات موضوعية: vibration-mitigation techniques, wave propagation, soil dynamics, Engineering geology. Rock mechanics. Soil mechanics. Underground construction, TA703-712

الوصف: This paper presents a concept for vibration-mitigation techniques with the potential to reduce ground vibration amplitudes by applying an additional vibration source. The idea of an additional generator is verified in the case of an impact load for the points located on the ground surface and below it. Equations of motion for the damped transversally isotropic ground model with the absorbing boundary conditions are presented and numerically integrated using FlexPDE software, based on the finite element method. The efficiency of the solution is analyzed in terms of reducing the vertical and horizontal components. Results are presented in the form of a dimensionless amplitude reduction factor. In each case being analyzed, a vibration mitigation effect in a three-story building was achieved.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/2083-831XTest

الوصول الحر: https://doaj.org/article/4e9e43e975d146aaa5e75fa0bcf90fd6Test

المؤلفون: Danilov, Mikhail, Karpov, Arkadi

المصدر: Advances in Materials Science; Dec2018, Vol. 18 Issue 4, p318-325, 8p

مصطلحات موضوعية: METEORS, ARTIFICIAL neural networks, RADIO wave propagation, ASTRONOMICAL observations

مستخلص: An artificial neural network is described for classification of meteor trails into the distinct overdense, intermediate and underdense trail categories. The neural network was trained and on model data obtained using the "KAMET" program and tested on real data. The best result of classification success rate of 95% without according to the heights of the formation of meteor trails. Results of classification with according to the heights of the formation of meteor trails are 82% - 91%. [ABSTRACT FROM AUTHOR]

: Copyright of Advances in Materials Science is the property of Sciendo 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: Gajewski Sławomir

المصدر: Polish Maritime Research, Vol 23, Iss 1, Pp 12-19 (2016)

مصطلحات موضوعية: marine radio communication, wave propagation at sea, ground-to-sea communication, ground-to-air communication, ofdm system design, safety at sea, Naval architecture. Shipbuilding. Marine engineering, VM1-989

الوصف: In the paper the study of radio communication system design process for systems based on OFDM transmission is considered. The signal propagation model for 1.4 GHz frequency band is discussed, and the study of signal propagation characteristics, important from the point of view of OFDM system design, is presented. The methodology of OFDM interface design is proposed and some characteristics of the OFDM-based radio communication system are analysed.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/2083-7429Test

الوصول الحر: https://doaj.org/article/3ac200a6436644ac9d57cc22da857cb1Test