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Matched field processing (MFP) is an established technique for source localization in known multipath acoustic environments. Unfortunately, in many situations, imperfect knowledge of the actual propagation environment and sidelobes due to modal interference prevent accurate propagation modeling and source localization via MFP. To suppress the sidelobes and improve the method's robustness, a linear frequency-difference matched field processing (LFDMFP) method for estimating the source range is proposed. A two-neighbor-frequency high-order cross-spectrum between the measurement and the replica of each hydrophone of the vertical line array is first computed. The cost function can then be derived from the dual summation or double integral of the high-order cross-spectrum with respect to the depth of the hydrophones and the candidate sources of the replicas, where the range that corresponds to the minimum is the optimal estimation. Because of the larger modal interference distances, LFDMFP can efficiently provide only one optimal range within the same range search interval rather than some conventional matched field processing. The efficiency of the presented method was verified using simulations and experiments. The LFDMFP unambiguously estimated the source range in two experimental datasets with average relative errors of 2.2 and 1.9%. [ABSTRACT FROM AUTHOR]

The dynamical characteristics of the zonal wavenumber 1 (s = 1) Rossby-gravity (RG) wave are examined using recently available reanalysis data for the whole neutral atmosphere over 16 years. An isolated peak is detected in the two-dimensional zonal wavenumber-frequency spectra that likely corresponds to the theoretically-expected s = 1 RG mode at heights of z = 30, 50, 65, and 80 km. The wave period of the spectral peak is approximately 1.3 days, which is close to one day. The s = 1 RG wave is successfully extracted using a band-pass filter after removing the diurnal tide with quite large amplitudes. The s = 1 RG wave exhibits a characteristic seasonal variation: the geopotential height (GPH) amplitudes are largest in the winter hemisphere in the stratosphere and lower mesosphere while enhancement is observed in both the winter and summer hemispheres in the upper mesosphere. Phase structures are examined in detail for a strong case. The horizontal phase structure at each height is consistent with the normal mode theory. The vertical phase structure is approximately barotropic from the lower stratosphere to the upper mesosphere at 30°N and 30°S where the amplitudes are large. [ABSTRACT FROM AUTHOR]

This study investigates the thermo-mechanical behavior of generalized thermoelastic mediums under the influence of gravitational fields, incorporating two-temperature effects through the Lord–Shulman and dual-phase-lag models. Focusing on a plane surface subjected to an arbitrary normal force and maintained at isothermal conditions, analytical expressions for conductive temperature, thermodynamic temperature, displacement components, and force stresses are derived using normal mode analysis. Numerical results, presented graphically, consider the application of thermal force. Comparative analyses between the dual-phase-lag and Lord-Shulman models are conducted, examining the impact of gravity and the two-temperature effect. Engineering applications of these findings can enhance the understanding of thermal management in materials subjected to varying gravitational environments, such as aerospace structures and thermal barrier coatings. [ABSTRACT FROM AUTHOR]

Data-derived normal mode extraction is an effective method for extracting normal mode depth functions in the absence of marine environmental data. However, when the corresponding singular vectors become nonunique when two or more singular values obtained from the cross-spectral density matrix diagonalization are nearly equal, this results in unsatisfactory extraction outcomes for the normal mode depth functions. To address this issue, we introduced in this paper a range-difference singular value decomposition method for the extraction of normal mode depth functions. We performed the mode extraction by conducting singular value decomposition on the individual frequency components of the signal's cross-spectral density matrix. This was achieved by using pressure and its range-difference matrices constructed from vertical line array data. The proposed method was validated using simulated data. In addition, modes were successfully extracted from ambient noise. [ABSTRACT FROM AUTHOR]

This manuscript addresses a significant research gap in the study by employing a mathematical model of photo thermoelastic wave propagation in a rotator semiconductor medium under the effect of a magnetic field and initial stress, as well as ramp-type heating. The considered model is formulated during the photothermal theory and in two-dimensional (2D) electronic-elastic deformation. The governing equations represent the interaction between the primary physical parameters throughout the process of photothermal transfer. Computational simulations are performed to determine the temperature, carrier density, displacement components, normal stress, and shear stress using the application of Lame's potential and normal mode analysis. Numerical calculations are carried out and graphically displayed for an isotropic semiconductor like silicon (Si) material. Furthermore, comparisons are made with the previous results obtained by the others, as well as in the presence and absence of magnetic field, rotation, and initial stress. The obtained results illustrate that the rotation, initial stress, magnetic field, and ramp-type heating parameter all have significant effects. This investigation provides valuable insights into the synergistic dynamics among a magnetization constituent, semiconducture structures, and wave propagation, enabling advancements in nuclear reactors' construction, operation, electrical circuits, and solar cells. [ABSTRACT FROM AUTHOR]

We consider circular Rayleigh problem which is incompressible, inviscid axial flows to axisymmetric disturbances. For this problem, we derived unbounded parabolic instability region which intersects with Batchelor and Gill semicircle instability region under certain condition. This has been illustrated with examples. Furthermore, we obtained supremum bound for the growth rate of an unstable mode, amplification factor. [ABSTRACT FROM AUTHOR]

The poro-thermoelastic problem with two-temperature, under the influence of the gravitational field and the rotation was investigated. The solution to the problem is presented in the context of lord and Shulman's theory of thermoelasticity with one relaxation time. We applied normal mode analysis to solve the resulting non-dimensional coupled partial differential equations. Effect of rotation, gravitational field, two-temperature parameter and porosity parameter on non-dimensional displacements, thermodynamic temperature, conductive temperature, excess pore water pressure and stresses has been discussed. Numerical analyses are given graphically in the square (2D) to illustrate the effect of these parameters. Some particular cases of interest are deduced from the present investigation. [ABSTRACT FROM AUTHOR]

A unique three-dimensional model of generalized thermoelasticity, incorporating a single relaxation time and relying on stress gradient nonlocal elasticity, is presented in this study. The fundamental coupled equations governing the model are applied to a semi-infinite spatial medium with a rigidly fixed bounding surface, which is exposed to a time-dependent thermal shock. The general solution for the field variables is obtained in a closed form through the utilization of normal mode analysis and the eigenvalue approach technique. Numerical results, specific to a substance resembling copper, are provided for the field variables. Parametric studies are conducted to assess the impact of elastic nonlocality on various physical quantities. The graphical representation reveals a noteworthy influence of the nonlocal parameter on the field variables. The study further discusses and compares predictions from the new model with the Lord and Shulman theory of generalized thermoelasticity. Ultimately, the article concludes with a summary of key remarks. [ABSTRACT FROM AUTHOR]

Normal mode separation and information extraction are popular topics in marine acoustics. The extraction of modal wavenumbers and modal depth functions using the data of a vertical line array is beneficial to various applications. In this paper, we systematically introduce a normal mode separation method based on the consistency restraint of the horizontal wavenumber, obtain the modal depth functions using the singular value decomposition (SVD) method, determine the vertical distribution of the horizontal wavenumber, and determine the SVD accuracy by the consistency of modal wavenumbers on the vertical direction. Moreover, this method can be used to determine the SVD accuracy without true depth functions. When the degeneracy problem leads to a poor SVD effect, the linear relation between the degenerate and true modes is obtained, and the minimum standard deviation of the vertical distribution of the modal wavenumbers is taken as the loss function, thus optimizing the SVD result and improving the accuracy of modal wavenumber estimation. The proposed method is validated using simulated data. In addition, the modes are successfully extracted from ambient noise.

Matched field processing (MFP) is an established technique for source localization in known multipath acoustic environments. Unfortunately, in many situations, imperfect knowledge of the actual propagation environment and sidelobes due to modal interference prevent accurate propagation modeling and source localization via MFP. To suppress the sidelobes and improve the method’s robustness, a linear frequency-difference matched field processing (LFDMFP) method for estimating the source range is proposed. A two-neighbor-frequency high-order cross-spectrum between the measurement and the replica of each hydrophone of the vertical line array is first computed. The cost function can then be derived from the dual summation or double integral of the high-order cross-spectrum with respect to the depth of the hydrophones and the candidate sources of the replicas, where the range that corresponds to the minimum is the optimal estimation. Because of the larger modal interference distances, LFDMFP can efficiently provide only one optimal range within the same range search interval rather than some conventional matched field processing. The efficiency of the presented method was verified using simulations and experiments. The LFDMFP unambiguously estimated the source range in two experimental datasets with average relative errors of 2.2 and 1.9%.

The use of autonomous vehicles (AVs) in transportation at signalized intersections is proposed to improve safety, efficiency, and sustainability. The discussion shall thus focus more on the impacts of different AV driving behaviors to some key transportation metrics solely at signalized intersections. Among the parameters considered are travel time, queue length, delay, and speed. This is clear from one such holistic study that Cautious AV behavior would reduce accidents, but on the other way around, it might increase traffic delays and lead to congestion at signalized junctions. Aggressive AVs will improve the flow of traffic but face problems in safety in this kind of set-up. Normal AV operation A balanced approach that offers intermediary levels of travel time and safety. The review further investigates the environmental effects of various driving patterns within signalized intersections, where it notes that there are noticeable differences in emissions and fuel consumed if the driving behavior is taken into consideration. It goes further into the implications for traffic management and control systems, noting challenges and opportunities while integrating AVs into existing infrastructure and spotlighting at signalized intersections. Paramount to the review are the considerations of safety, regulatory frameworks, and mitigating strategies relevant to AV behavior at signalized intersections. In so doing, this review seeks to inform future research and policy decisions with a nuanced understanding of how various AV driving behaviors affect signalized intersection performance, seeking to optimize AV benefits while mitigating possible risks at critical traffic junctures. [ABSTRACT FROM AUTHOR]

The purpose of the current study is to establish the deformation in a two-dimensional, isotropic, rotating half-space with gravitational field and initial stress that also has a heat source at the half boundary-space under magnetic field for Green and Naghdi II model. For the solution of the required problem, the methodologies of normal mode and approximate eigenvalues has been utilized. For graphical representation of different physical quantities such as displacement components, stress components, as well as the temperature distribution, Matlab software has been used. These results were compared with previous results in the same direction, and it was found that the treatment method for the aforementioned problem may form a basis for examining the effect of each of the gravitational field, magnetic field, rotation, and initial pressure on a thermally elastic body in the form of half an area without energy decay when neglecting some external influences. [ABSTRACT FROM AUTHOR]