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1دورية أكاديمية
المؤلفون: Andrew T. Peplow, Bilong Liu
المصدر: Foundations, Vol 4, Iss 2, Pp 205-224 (2024)
مصطلحات موضوعية: wave propagation, linear elastic material, matrix scaling, zero group velocity, path following, Mathematics, QA1-939
الوصف: This paper introduces an efficient computational procedure for analyzing the propagation of harmonic waves in layered elastic media. This offers several advantages, including the ability to handle arbitrary frequencies, depths, and the number of layers above an elastic half-space, and efforts to follow dispersion curves and flag up possible singularities are investigated. While there are inherent limitations in terms of computational accuracy and capacity, this methodology is straightforward to implement for studying free or forced vibrations and obtaining relevant response data. We present computations of wavenumber dispersion diagrams, phase velocity plots, and response data in both the frequency and time domains. These computational results are provided for two example cases: plane strain and axisymmetry. Our methodology is grounded in a well-conditioned dynamic stiffness approach specifically tailored for deep-layered strata analysis. We introduce an innovative method for efficiently computing wavenumber dispersion curves. By tracking the slope of these curves, users can effectively manage continuation parameters. We illustrate this technique through numerical evidence of a layer resonance in a real-life case study characterized by a fold in the dispersion curves. Furthermore, this framework is particularly advantageous for engineers addressing problems related to ground-borne vibrations. It enables the analysis of phenomena such as zero group velocity (ZGV), where a singularity occurs, both in the frequency and time domains, shedding light on the unique characteristics of such cases. Given the reduced dimension of the problem, this formulation can considerably aid geophysicists and engineers in areas such as MASW or SASW techniques.
وصف الملف: electronic resource
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2دورية أكاديمية
المصدر: Modelling, Vol 5, Iss 2, Pp 458-482 (2024)
مصطلحات موضوعية: numerical modeling, integrated modeling, coastal processes, mild slope, wave propagation, wave reflection, Engineering design, TA174
الوصف: Numerical modeling of wave transformation, hydrodynamics, and morphodynamics in coastal regions holds paramount significance for combating coastal erosion by evaluating and optimizing various coastal protection structures. This study aims to present an integration of numerical models to accurately simulate the coastal processes with the presence of coastal and harbor structures. Specifically, integrated modeling employs an advanced mild slope model as the main driver, which is capable of describing all the wave transformation phenomena, including wave reflection. This model provides radiation stresses as inputs to a hydrodynamic model based on Reynolds-averaged Navier–Stokes equations to simulate nearshore currents. Ultimately, these models feed an additional model that can simulate longshore sediment transport and bed level changes. The models are validated against experimental measurements, including energy dissipation due to bottom friction and wave breaking; combined refraction, diffraction, and breaking over a submerged shoal; wave transformation and wave-generated currents over submerged breakwaters; and wave, currents, and sediment transport fields over a varying bathymetry. The models exhibit satisfactory performance in simulating all considered cases, establishing them as efficient and reliable integrated tools for engineering applications in real coastal areas. Moreover, leveraging the validated models, a numerical investigation is undertaken to assess the effects of wave reflection on a seawall on coastal processes for two ideal beach configurations—one with a steeper slope of 1:10 and another with a milder slope of 1:50. The numerical investigation reveals that the presence of reflected waves, particularly in milder bed slopes, significantly influences sediment transport, emphasizing the importance of employing a wave model that takes into account wave reflection as the primary driver for integrated modeling of coastal processes.
وصف الملف: electronic resource
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3دورية أكاديمية
المؤلفون: Oscar Scussel, Michael J. Brennan, Jennifer M. Muggleton, Fabrício C. L. de Almeida, Phillip F. Joseph, Yan Gao
المصدر: Acoustics, Vol 6, Iss 1, Pp 157-176 (2024)
مصطلحات موضوعية: leak noise wave propagation, predominantly fluid-borne wavenumber, buried plastic water pipes, wave dynamic stiffness, Physics, QC1-999
الوصف: In buried plastic water pipes, the predominantly fluid-borne wave is of particular interest, as it plays a key role in the propagation of leak noise. Consequently, it has been studied by several researchers to determine the speed of wave propagation and its attenuation with distance. These features are encapsulated in the wavenumber. By examining the factors that govern the behaviour of this wavenumber, this paper presents an in-depth examination of the physical mechanisms of leak noise propagation. To achieve this, an alternative physics-based model for the wavenumber is developed, using the concept of the wave dynamic stiffnesses of the individual components within the pipe system, i.e., the water in the pipe, the pipe wall, and the surrounding medium. This facilitates a clear interpretation of the wave behaviour in terms of the physical properties of the system, especially the interface between the pipe and the surrounding medium, which can have a profound influence on the leakage of acoustic energy from the pipe wall into the external medium. Three systems with different types of surrounding medium are studied, and the factors that govern leak noise propagation in each case are identified. Experimental results on two distinct test sites from different parts of the world are provided to validate the approach using leak noise as an excitation mechanism.
وصف الملف: electronic resource
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4دورية أكاديمية
المؤلفون: Sun-Hoon Kim, Kwang-Jin Kim
المصدر: Applied Mechanics, Vol 5, Iss 1, Pp 141-161 (2024)
مصطلحات موضوعية: earthquake, free-field analysis, frequency domain analysis, time domain analysis, finite element analysis, shear wave propagation, Engineering (General). Civil engineering (General), TA1-2040
الوصف: In Korea, the underground silo structure for low- and intermediate-level radioactive waste disposal facilities has been constructed and operated since 2014. Large-scale earthquakes occurred in 2016 and 2017, respectively, in Gyeongju and Pohang areas near the underground silo structures, and interest in the stability of the underground silo increased significantly. In this paper, one-dimensional free-field analyses have been carried out before the three-dimensional silo dynamic analyses subjected to earthquake loadings. As an additional study, a new form of the finite element equilibrium equation is derived in terms of relative motions, which is essentially the same equation expressed in terms of total motions where the base shear force is applied to the earthquake load. The accuracy of conventional finite element solutions is evaluated by directly comparing them with closed-form solutions by frequency domain analysis such as SHAKE91.
وصف الملف: electronic resource
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5دورية أكاديمية
المؤلفون: Angelo Morro
المصدر: Dynamics, Vol 3, Iss 3, Pp 563-580 (2023)
مصطلحات موضوعية: Korteweg fluids, quantum hydrodynamics, higher-order gradients, non-local equations, thermodynamic consistency, wave propagation, Thermodynamics, QC310.15-319, Biochemistry, QD415-436
الوصف: This paper investigates the modelling of Korteweg-type fluids and hence the dependence of the stress tensor on gradients of mass density. This topic, originating from the need for describing capillarity effects, is mainly of interest in connection with nanosystems where the mean free path may be comparable with the geometric dimensions of the system. In addition to the Korteweg fluid model, the paper gives a review of the stress tensor function arising in quantum fluid hydrodynamics. Next, thermodynamic consistency is established for a fluid involving first- and second-order density gradients. The modelling investigated is a generalization of the classical Korteweg fluid and allows a better understanding of previous thermodynamic restrictions. The restrictions determined for the general scheme with second-order gradients are applied to the particular cases of the Korteweg fluid and the quantum fluid. Further, to allow for discontinuity wave solutions with finite speed of propagation, a model is established which involves higher-order derivatives and reduces to the Korteweg fluid in stationary conditions.
وصف الملف: electronic resource
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6دورية أكاديمية
المؤلفون: Wenjie Zhou, Yanjun Li, Yulu Zhang, Qingyan Jiang, Dong Chen, Yanzhen Gu, Yuan Lin
المصدر: Journal of Marine Science and Engineering, Vol 12, Iss 6, p 889 (2024)
مصطلحات موضوعية: buoy response, typhoon doksuri, cable seafloor observatory, ocean multidisciplinary observation, wave propagation, Naval architecture. Shipbuilding. Marine engineering, VM1-989, Oceanography, GC1-1581
الوصف: In order to address the requirements of scientific multidisciplinary observation in diverse small-scale regions, we have introduced the Buoy-based Cable Seafloor Observatory System (BCSOS). This system offers a distinct advantage in contexts where the use of shorter cables is feasible, contrasting with the lengthy cables typically necessary for conventional observatories. The BCSOS consists of three primary components: the Real-Time Electric Communication (RTEC) Buoy, the Power Information Transmission System (PITS), and the Seafloor Observation Subsystem (SOS). The RTEC Buoy is equipped with instruments for measuring sea surface parameters and serves as a data and power hub. The PITS, comprising a robust EM cable, connects the buoy to the SOS, which houses instruments for seafloor observations. The system is designed for a maximum water depth of 100 m and has an expected lifespan of about 5 years. The BCSOS prototypes were deployed at the Huangqi Peninsula, Fujian Province, and successfully documented the process during Typhoon Doksuri (international code 2305) at the end of July 2023. The recorded data from the BCSOS revealed a significant increase in wave height and period as the storm approached the Huangqi Peninsula. Additionally, the RTEC buoy exhibited a notable response to the large waves. The data analysis revealed a distinct pattern between the buoy response and the direction of wave propagation across various sea conditions, that the buoy’s angular movement in pitch and roll directions follows a regular elliptical distribution corresponding to different wave propagation directions. Upon thorough evaluation, future enhancements to the system are slated to concentrate on refining its design, with a particular emphasis on bolstering stability and enhancing corrosion resistance. These improvements are aimed at cementing the system’s long-term viability and performance within the challenging marine environment.
وصف الملف: electronic resource
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7دورية أكاديمية
المصدر: Materials, Vol 17, Iss 10, p 2369 (2024)
مصطلحات موضوعية: ligament structure, band gap, frequency–response, wave propagation, Technology, Electrical engineering. Electronics. Nuclear engineering, TK1-9971, Engineering (General). Civil engineering (General), TA1-2040, Microscopy, QH201-278.5, Descriptive and experimental mechanics, QC120-168.85
الوصف: Honeycomb structures have attracted much attention for their excellent characteristics of reducing vibration and noise in recent years. In this study, through band analysis of different ligament structures, we aim to optimize the design of a steel structure that can isolate most of the noise in the 1500–5000 Hz range. The present study examines several different chiral structures. We calculate the band gaps of chiral structures under different geometric configurations and identify the variations in band gaps with geometric layouts. It is found that compared to other chiral structures, the triligaments chiral structure exhibits excellent band gap characteristics. The calculation results demonstrate that enhancing axial symmetry while filling central nodes can effectively enhance the structure’s band gap properties. Frequency–response functions of different lattice structures are computed, and the results align with the calculations of band structures. This study then analyzes the influence of the number of periods on the magnitude of vibration attenuation, revealing that under the same number of periods, the wider the band gap of the structure, the greater the vibration attenuation. Both the triligaments chiral structure and the vertical triligaments structure possess ideal band gap widths, effectively suppressing wave propagation. Subsequently, harmonic response analyses and transient wave calculations further validate the accuracy of the band structure and frequency–response curve calculations. Our study results provide a new way to design a sound insulation structure that can isolate noise signals within the frequency range from 1500 to 5000 Hz in engineering.
وصف الملف: electronic resource
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8دورية 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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9دورية 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.
العلاقة: https://www.mdpi.com/1424-8220/24/1/282Test; https://doaj.org/toc/1424-8220Test; https://doaj.org/article/6d18aaf2fbbd42dbb49ddc5ea3f653d3Test
الإتاحة: https://doi.org/10.3390/s24010282Test
https://doaj.org/article/6d18aaf2fbbd42dbb49ddc5ea3f653d3Test -
10دورية أكاديمية
المؤلفون: Huadian Zhang, Arunachalam M. Rajendran, Manoj K. Shukla, Sasan Nouranian, Ahmed Al-Ostaz, Steven Larson, Shan Jiang
المصدر: Journal of Composites Science, Vol 8, Iss 5, p 159 (2024)
مصطلحات موضوعية: layered ceramic–polymer–metal composites, plate impact simulation, stress wave propagation, finite element method, Abaqus, VUMAT, Technology, Science
الوصف: This paper presents a numerical study on the dynamic response and impact mitigation capabilities of layered ceramic–polymer–metal (CPM) composites under plate impact loading, focusing on the layer sequence effect. The layered structure, comprising a ceramic for hardness and thermal resistance, a polymer for energy absorption, and a metal for strength and ductility, is analyzed to evaluate its effectiveness in mitigating the impact loading. The simulations employed the VUMAT subroutine of DSGZ material models within Abaqus/Explicit to accurately represent the mechanical behavior of the polymeric materials in the composites. The VUMAT implementation incorporates the explicit time integration scheme and the implicit radial return mapping algorithm. A safe-version Newton–Raphson method is applied for numerically solving the differential equations of the J2 plastic flow theory. Analysis of the simulation results reveals that specific layer configurations significantly influence wave propagation, leading to variations in energy absorption and stress distribution within the material. Notably, certain layer sequences, such as P-C-M and C-P-M, exhibit enhanced impact mitigation with a superior ability to dissipate and redirect the impact energy. This phenomenon is tied to the interactions between the material properties of the ceramic, polymer, and metal, emphasizing the necessity of precise material characterization and enhanced understanding of the layer sequencing effect for optimizing composite designs for impact mitigation. The integration of empirical data with simulation methods provides a comprehensive framework for optimizing composite designs in high-impact scenarios. In the general fields of materials science and impact engineering, the current research offers some guidance for practical applications, underscoring the need for detailed simulations to capture the high-strain-rate dynamic responses of multilayered composites.
وصف الملف: electronic resource
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