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A general theory for solving electromagnetic diffraction problems with impenetrable/penetrable wedges immersed in/made of an arbitrary linear (bianistropic) medium is presented. This novel and general spectral theory handles complex scattering problems by using transverse equations for layered planar and angular structures, the characteristic Green function procedure, the Wiener–Hopf technique, and a new methodology for solving GWHEs. The technique has been proven effective for analyzing problems involving wedges immersed in isotropic media; in this study, we extend the theory to more general cases while providing all necessary mathematical tools and corresponding validations. We obtain generalized Wiener–Hopf equations (GWHEs) from spectral functional equations in angular regions filled by arbitrary linear media. The equations can be interpreted with a network formalism for a systematic view. We recall that spectral methods (such as the Sommerfeld–Malyuzhinets (SM) method, the Kontorovich–Lebedev (KL) transform method, and the Wiener–Hopf (WH) method) are well-consolidated, fundamental, and effective tools for the correct and precise analysis of electromagnetic diffraction problems constituted by abrupt discontinuities immersed in media with one propagation constant, although they are not immediately applicable to multiple-propagation-constant problems. To the best of our knowledge, the proposed mathematical technique is the first extension of spectral analysis to electromagnetic problems in the presence of angular regions filled by complex arbitrary linear media, thereby providing novel mathematical tools. Validation through fundamental examples is proposed. [ABSTRACT FROM AUTHOR]

The paper presents particular issues of mudflow dynamics, one of the hazardous natural disasters, namely the theoretical study of the flow power during mudflow movement in the wave regime taking into account its rheological properties. The paper discusses the physical process of mudflow mass impetus accumulated in erosion banks, taking into account the impact of the tense state of the eroded mass, in particular, similar to soil mechanics problems, the density of the mudflow-forming mass (ρ), the free fall acceleration (g), angle of internal friction (φ), the adhesive force (Pe), the height equivalent to pressure (h′), the height of the mudflow-forming mass (H), the intensity of transverse pressure (P), and the value of the active pressure of the inertial mass cohesion (C) on the deformation mode of the mudflow mass. On the basis of the basic equations of mudflow dynamics and theoretical studies, an equation is obtained to calculate the values of flow power when mudflows move in the wave mode, taking into account the main rheological properties of a mudflow mass. [ABSTRACT FROM AUTHOR]

In this paper, the coupled sloshing and motion characteristics of a cylindrical floating production storage offloading (CFPSO) are numerically investigated by means of computational fluid dynamics (CFD) tool. The simulations are performed using an in-house CFD solver naoe-FOAM-SJTU which is developed based on OpenFOAM. The active wave generating-absorbing boundary condition (GABC) is utilized for wave generation and absorption. The stabilized k-omega SST turbulence model are used to avoid excessive eddy viscosity near the free surface. CFPSO with and without partially filled liquid tanks in regular waves with different wave periods are simulated and vertical planar motions such as surge, heave and pitch response amplitude operators (RAOs) are compared. Forces due to liquid sloshing and wave loads are extracted and analyzed. The free surface motions inside liquid tanks in one wave period presented to explain the motion characteristics. [ABSTRACT FROM AUTHOR]

The paper presents particular issues of mudflow dynamics, one of the hazardous natural disasters, namely the theoretical study of the flow power during mudflow movement in the wave regime taking into account its rheological properties. The paper discusses the physical process of mudflow mass impetus accumulated in erosion banks, taking into account the impact of the tense state of the eroded mass, in particular, similar to soil mechanics problems, the density of the mudflow-forming mass (ρ), the free fall acceleration (g), angle of internal friction (φ), the adhesive force (Pe), the height equivalent to pressure (h′), the height of the mudflow-forming mass (H), the intensity of transverse pressure (P), and the value of the active pressure of the inertial mass cohesion (C) on the deformation mode of the mudflow mass. On the basis of the basic equations of mudflow dynamics and theoretical studies, an equation is obtained to calculate the values of flow power when mudflows move in the wave mode, taking into account the main rheological properties of a mudflow mass.

A general theory for solving electromagnetic diffraction problems with impenetrable/penetrable wedges immersed in/made of an arbitrary linear (bianistropic) medium is presented. This novel and general spectral theory handles complex scattering problems by using transverse equations for layered planar and angular structures, the characteristic Green function procedure, the Wiener–Hopf technique, and a new methodology for solving GWHEs. The technique has been proven effective for analyzing problems involving wedges immersed in isotropic media; in this study, we extend the theory to more general cases while providing all necessary mathematical tools and corresponding validations. We obtain generalized Wiener–Hopf equations (GWHEs) from spectral functional equations in angular regions filled by arbitrary linear media. The equations can be interpreted with a network formalism for a systematic view. We recall that spectral methods (such as the Sommerfeld–Malyuzhinets (SM) method, the Kontorovich–Lebedev (KL) transform method, and the Wiener–Hopf (WH) method) are well-consolidated, fundamental, and effective tools for the correct and precise analysis of electromagnetic diffraction problems constituted by abrupt discontinuities immersed in media with one propagation constant, although they are not immediately applicable to multiple-propagation-constant problems. To the best of our knowledge, the proposed mathematical technique is the first extension of spectral analysis to electromagnetic problems in the presence of angular regions filled by complex arbitrary linear media, thereby providing novel mathematical tools. Validation through fundamental examples is proposed.

The purpose of this article is to derive a class of multi-soliton solutions of the Burgers equation employing Darboux transformation with the help of the Lax pair. By means of an effective transformation, the Burgers equation is reduced to a suitable form, and accordingly, the Lax pair of the said equation is derived utilising the Ablowitz–Kaup–Newell–Segur (AKNS) approach. Thus, the integrability of the Burgers equation is confirmed. To find an effective solution for the Burgers equation, for the first time, we apply the Darboux transformation through the Lax pair and explore new types of one-soliton solutions and two-soliton solutions of the Burgers equation. These solutions provide some new features of the Burgers equation. To the best of our knowledge, this is the first study in which a parabolic type of structure is found in the Burgers system. Moreover, taking these solutions as the seed solution, higher-order multi-soliton solution can also be generated. Finally, some important three-dimensional plots of the wave solutions are presented to visualise the dynamics of the model. [ABSTRACT FROM AUTHOR]

The six-degree-of-freedom (6 DOF) motion of the mother-ship, which is caused by wave fluctuation, makes offshore operations difficult. To solve this problem, various heave compensation systems were proposed, as well as the law of wave motion. These heave compensation systems included passive heave compensation system, semi-active heave compensation system, and active heave compensation (AHC) system. However, the empirical formula of wave motion is not suitable for practical offshore operations, and rare AHC systems take the characteristic of compensation into consideration. To study the compensation characteristic of the AHC system based on electric-driven marine winch in the actual sea condition and improve the accuracy of compensation, this work uses the measured data of wave motion, and deduces the motion equations of multi-axial driving system. By substituting the above elements into the AHC system and designing the sliding mode controller (SMC), the simulation results show the ideal compensation effect of the system. By comparing with experimental results, it is concluded that the driving system operates in according with the specified states, and the compensation performance of system is effective. The overall work is conductive to the research on AHC system, as well as the exploitation of marine resources. [ABSTRACT FROM AUTHOR]

It is well known that the kinetic and potential energies of a system governed by a linear wave equation are equipartitioned in a finite time. This result has been extended by previous researchers to several physical settings: elastodynamics, electrodynamics, and micropolar elasticity. In the case of a helix, there is a direct coupling of longitudinal and torsional wave motions due to the structure of constitutive relations. Providing that the initial conditions functions have compact support, we demonstrate that the equipartition phenomenon occurs after a finite time in this case as well—i.e. the potential energy and the kinetic energy of a helix become equal and remain constant after a finite time. [ABSTRACT FROM AUTHOR]

The objective of this article is to make a comparison in a computational environment between an alternating current motor and a direct current motor is made for dynamic variations in the propulsion of an artisanal fishing boat. Initially, the boat was simulated in the Maxsurf software to obtain the dynamic behaviors for pitching, rolling, yawing, and heave motions with wind and wave perturbations for a Pierson Moskowitz spectrum. Subsequently, the motors are selected and in Matlab/Simulink software and a torque behavior required by the vessel to act on the resistance presented in each dynamic motion is proposed. This allows for analyzing the required mechanical and electrical conditions, using the curves obtained in the simulation. Finally, it is concluded that taking into account the criteria of torque, power, speed, and current, the results obtained show that the DC motor is more efficient than the three-phase AC motor for artisanal fishing vessel applications. In addition, the two motors require greater effort to overcome the disturbance related to the rolling motion in the steady-state, while in the transient state the DC motor requires a higher starting torque and the AC motor presents oscillations, which are undesirable disturbances because they produce instability in the electrical system. Additionally, it is important to take into account the energy source that feeds the motors, which can be alternating current or direct current.

Human Mesenchymal Stem Cells (hMSCs) and their derived products hold potential in tissue engineering and as therapeutics in a wide range of diseases. hMSCs possess the ability to aggregate into "spheroids", which has been used as a preconditioning technique to enhance their therapeutic potential by upregulating stemness, immunomodulatory capacity, and anti-inflammatory and pro-angiogenic secretome. Few studies have investigated the impact on hMSC aggregate properties stemming from dynamic and static aggregation techniques. hMSCs' main mechanistic mode of action occur through their secretome, including extracellular vesicles (EVs)/exosomes, which contain therapeutically relevant proteins and nucleic acids. In this study, a 3D printed microchannel bioreactor was developed to dynamically form hMSC spheroids and promote hMSC condensation. In particular, the manner in which dynamic microenvironment conditions alter hMSC properties and EV biogenesis in relation to static cultures was assessed. Dynamic aggregation was found to promote autophagy activity, alter metabolism toward glycolysis, and promote exosome/EV production. This study advances our knowledge on a commonly used preconditioning technique that could be beneficial in wound healing, tissue regeneration, and autoimmune disorders. [ABSTRACT FROM AUTHOR]

The question of how soft polymers slide against hard surfaces is of significant scientific interest, given its practical implications. Specifically, such systems commonly show interesting stick–slip dynamics, wherein the interface moves intermittently despite uniform remote loading. The year 2021 marked the 50th anniversary of the publication of a seminal paper by Adolf Schallamach (Wear, 1971), which first revealed an intimate link between stick–slip and moving detachment waves, now called Schallamach waves. We place Schallamach's results in a broader context and review subsequent investigations of stick–slip, before discussing recent observations of solitary Schallamach waves. This variant is not observable in standard contacts so that a special cylindrical contact must be used to quantify its properties. The latter configuration also reveals the occurrence of a dual wave—the so-called separation pulse—that propagates in a direction opposite to Schallamach waves. We show how the dual wave and other, more general, Schallamach-type waves can be described using continuum theory and provide pointers for future research. In the process, fundamental analogues of Schallamach-type waves emerge in nanoscale mechanics and interface fracture. The result is an ongoing application of lessons learnt from Schallamach-type waves to better understand these latter phenomena. This article is part of the theme issue 'Nanocracks in nature and industry'. [ABSTRACT FROM AUTHOR]

In this paper, an analytical method is developed for the axisymmetric dynamic response of a finite thickness liquid layer overlying a transversely isotropic porous solid half-space due to body waves. Potential functions and integral transforms are used together to handle the equations of wave motion in two media. The time-harmonic excitation with axisymmetric shape is assumed to be distributed in the interface of liquid and porous media. Green’s functions of stress and displacement are derived as closed-form integral expressions. Demonstration of the effect of the liquid thickness, degree of material anisotropy, and frequency of excitation on the dynamic response is considered here. Numerical results for a uniform distributed disk load are comprised with the existing elastic and poroelastic solutions to illustrate the quality of the method. The results of the current paper can be used in analysis and modelling the rigid or flexible foundations in marine structures.

The block medium is modeled by a discrete-periodic spatial lattice of masses connected by elastic springs and viscous dampers. To describe the viscoelastic behavior of the interblock layers, a rheological model of internal friction with two Maxwell elements and one Voigt element with the quality factor of the material as the determining parameter is proposed. Numerical experiments show that, within the framework of this interlayer model, it is possible to select the viscosity and stiffness of the Maxwell and Voigt elements so that the quality factor of the material differs from the given constant value by no more than 5%. In the one-dimensional case, within the framework of the proposed model, the influence of the quality factor on the dispersion properties of a block medium is studied and it is shown that the greatest effect of the quality factor on the dispersion is observed in the low-frequency part of the spectrum. In the three-dimensional case, within the framework of the proposed model, some geomechanical problems are numerically studied for a block half-space under the action of a surface concentrated vertical load. Namely, the attenuation of the velocity amplitudes of surface blocks was studied depending on the Q-factor under step action and under the action of a Gaussian pulse. In addition, we study a layer on the surface of a half-space under the action of a concentrated vertical impulse load in the case when both the layer and the half-space are block media but have different properties. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department 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.)

This paper reports a cellular automata (CA) study of the transient dynamic responses of anti-plane shear Lamb's problems on random fields (RFs) with fractal and Hurst effects. Both Cauchy and Dagum random field models are employed to capture the combined effects of spatial randomness in both mass density and stiffness tensor fields. First, with a dyadic representation, we formulate a second-rank anti-plane stiffness tensor random field (TRF) model with full anisotropy. Its statistical, fractal, and Hurst properties are investigated, leading to introduction of a so-called MOSP model of TRF. Then, we generalize the CA approach to incorporate the inhomogeneity in mass density as well as stiffness fields. Through parametric studies for both Cauchy and Dagum TRFs, the sensitivity of wave propagation on random fields is assessed for a wide range of fractal and Hurst parameters. In general, the mean response amplitude is lowered by the presence of randomness, and the Hurst parameter (especially, for β < 0.5 ) is found to have a stronger influence than the fractal dimension on the response. The results are compared with two simpler random fields: (1) randomness is present only in the mass density field; (2) randomness is present in the mass density field and in a locally isotropic stiffness tensor field. Overall, the results show that a second-rank anti-plane stiffness TRF with full anisotropy leads to the strongest fluctuation in displacement responses followed by a locally isotropic RF model. [ABSTRACT FROM AUTHOR]

The traditional wave motion characteristic experiment has some problems, such as the loose connection between theory and experimental teaching, limitations of the experiment due to its site and time, and poor sense of participation and interaction. Focusing on the above problems, a virtual simulation experiment system for wave motion characteristics is designed and developed. The system uses virtual reality technology, cloud platform technology, and wave simulation technology. Taking the real laboratory as the prototype, the scene structure, instrument function, and water movement are simulated with high precision. The multimode fusion teaching method has expanded the experimental content, enriched the micro‐observation function and data collection categories, enhanced the interaction of the experimental process, and created a high‐quality immersive online teaching experience for the students. Since its inception, the experiment system has served six cycles of instruction and obtained good feedback from the teachers and students. During the period of the pandemic, it provides great support to experimental teaching and serves as a good supplement to the existing teaching system. Adhering to the "student‐centered" teaching principle, the teaching team will improve the experimental system constantly, cultivate the students' independent thinking and innovation abilities, help the students with their own personalized development, and contribute to the training of excellent engineers. [ABSTRACT FROM AUTHOR]

In this work, we introduce a general method to deduce spectral functional equations in elasticity and thus, the generalized Wiener-Hopf equations (GWHEs), for the wave motion in angular regions filled by arbitrary linear homogeneous media and illuminated by sources localized at infinity. The work extends the methodology used in electromagnetic applications and proposes for the first time a complete theory to get the GWHEs in elasticity. In particular, we introduce a vector differential equation of firstorder characterized by a matrix that depends on the medium filling the angular region. The functional equations are easily obtained by a projection of the reciprocal vectors of this matrix on the elastic field present on the faces of the angular region. The application of the boundary conditions to the functional equations yields GWHEs for practical problems. This paper extends and applies the general theory to the challenging canonical problem of elastic scattering in angular regions. [ABSTRACT FROM AUTHOR]

The scaled boundary finite element method (SBFEM) developed by Wolf and Song has shown certain parallels to the finite element method (FEM) and boundary element method (BEM). Because of its semi‐analytical nature, SBFEM is particularly suitable for the analysis of wave propagation in unbounded domains. This paper makes a certain modification of the standard SBFEM. A new idea of scaling surface instead of a scaling center is introduced to formulate the governing SBFE equations for the analysis of wave propagation in multilayered half‐space, which leads to simplifying the modeling and saving considerably the computational effort. In addition, by employing the proposed approach, some problems encountered in engineering practice, which are difficult to deal with by the conventional SBFEM, for example, 3D foundation impedance on half‐space with irregular geographical features, can be effectively solved. The proposed approach also helps to simplify the solution of shell structures. Numerical examples are provided to validate the accuracy and efficiency of the proposed approach. [ABSTRACT FROM AUTHOR]

The coastline of the Gulf of Naples, Italy, is characterized by a series of infrastructures of strategic importance, including touristic and commercial ports between Pozzuoli to Sorrento, main roads, railways, and urban areas. Furthermore, the Gulf of Naples hosts an intense traffic of touristic and commercial maritime routes. The risk associated with extreme marine events is hence very significant over this marine and coastal area. On 28 December 2020, the Gulf of Naples was hit by an extreme sea storm, with severe consequences. This study focuses on the waterfront area of Via Partenope, where the waves overrun the roadway, causing massive damage on coastal seawall, road edges, and touristic structures (primarily restaurants). Based on the analysis of the meteorological evolution of the sea storm and its effects on the waterfront, we suggest that reflective processes induced on the sea waves by the tuff cliffs at the base of Castel dell'Ovo had an impact in enhancing the local-scale waves magnitude. This caused in turn severe flooding of the roadway and produced widespread damage along the coast. The analysis of the event of 28 December 2020, also suggests the need of an effective mitigation policy in the management of coastal issues induced by extreme sea storm events. Wind-based analysis and prediction of the sea wave conditions are currently discussed in the literature; however, critical information on wave height is often missing or not sufficient for reliable forecasting. In order to improve our ability to forecast the effects of sea storm events on the coastline, it is necessary to analyze all the components of the coastal wave system, including wave diffraction and reflection phenomena and the tidal change. Our results suggest in fact that only an integrated approach to the analysis of all the physical and anthropic components of coastal system may provide a correct base of information for the stakeholders to address coastal zone planning and protection. [ABSTRACT FROM AUTHOR]

Human Mesenchymal Stem Cells (hMSCs) and their derived products hold potential in tissue engineering and as therapeutics in a wide range of diseases. hMSCs possess the ability to aggregate into “spheroids”, which has been used as a preconditioning technique to enhance their therapeutic potential by upregulating stemness, immunomodulatory capacity, and anti-inflammatory and pro-angiogenic secretome. Few studies have investigated the impact on hMSC aggregate properties stemming from dynamic and static aggregation techniques. hMSCs’ main mechanistic mode of action occur through their secretome, including extracellular vesicles (EVs)/exosomes, which contain therapeutically relevant proteins and nucleic acids. In this study, a 3D printed microchannel bioreactor was developed to dynamically form hMSC spheroids and promote hMSC condensation. In particular, the manner in which dynamic microenvironment conditions alter hMSC properties and EV biogenesis in relation to static cultures was assessed. Dynamic aggregation was found to promote autophagy activity, alter metabolism toward glycolysis, and promote exosome/EV production. This study advances our knowledge on a commonly used preconditioning technique that could be beneficial in wound healing, tissue regeneration, and autoimmune disorders.

In this work, we introduce a general method to deduce spectral functional equations and, thus, the generalized Wiener–Hopf equations (GWHEs) for wave motion in angular regions filled by arbitrary linear homogeneous media and illuminated by sources localized at infinity with application to electromagnetics. The functional equations are obtained by solving vector differential equations of first order that model the problem. The application of the boundary conditions to the functional equations yields GWHEs for practical problems. This paper shows the general theory and the validity of GWHEs in the context of electromagnetic applications with respect to the current literature. Extension to scattering problems by wedges in arbitrarily linear media in different physics will be presented in future works. [ABSTRACT FROM AUTHOR]

The present paper is concerned with a study of water waves generated due to the presence of a line singularity (source) with time harmonic strength as well as impulsive strength through mangrove forests in the presence of a viscoelastic bed. The trunks of mangroves are assumed to be in the upper layer inviscid fluid, while the roots of mangroves are inside the viscoelastic bed. The equation of motion in the viscoelastic region is obtained by coupling the Voigt’s model with the equation of motion in the presence of mangroves. The expressions for the potential functions in the two layers are obtained. The forms of the surface and interface waves are depicted graphically for realistic values of kinematic viscosity and shear modulus of elasticity, the line source being submerged in the upper layer. [ABSTRACT FROM AUTHOR]

Rail corrugation, which causes the vibration and the noise, is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running. In the previous paper, we have already explained the growth mechanism and the wavelength determination mechanism of the rail corrugation from the dynamic point of view and that there are three stages in the evolution process of the corrugation: formation, growth and saturation. In this paper, we analyze the dynamic characteristics of the track and vehicle in the saturation stage, propose a growth curve of corrugation, and verify them based on measured data obtained on commercial lines. As a result, it is confirmed that when the roughness amplitude grows and exceeds the critical roughness amplitude, there are two characteristics: the significant increase of the contact force fluctuation and the acceleration of the rail and wheel, formation of higher-order roughness components of the corrugation. The growth curve of the corrugation can be approximated by a logistic function.

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office 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.)

The evaluation of hip hop dancers presently lacks clearly defined criteria and is often dependent on the subjective impressions of judges. Our study objective was to extract hidden motion characteristics that could potentially distinguish the skill levels of hip hop dancers and to examine the relationship between performance kinematics and judging scores. Eleven expert, six nonexpert, and nine novice dancers participated in the study, where each performed the "wave" motion as an experimental task. The movements of their upper extremities were captured by a motion capture system, and several kinematic parameters including the propagation velocity of the wave were calculated. Twelve judges evaluated the performances of the dancers, and we compared the kinematic parameters of the three groups and examined the relationship between the judging scores and the kinematic parameters. We found the coefficient of variation of the propagation velocity to be significantly different among the groups (P < .01) and highly correlated with the judging scores (r = -0.800, P < .01). This revealed that the variation of propagation velocity was the most dominant variable representing the skill level of the dancers and that the smooth propagation of the wave was most closely related to the evaluation by judges. [ABSTRACT FROM AUTHOR]

A multi-layer model is used to calculate time-dependent sediment velocity and concentration vertical profiles. This model, in which the differences in sediment transport at different distances from the bed are considered is intended both for the wave motion and steady flow. Numerical calculations were carried out for sediment transport during the wave crest and trough and total sediment transport as a sum of their absolute values. The model concept of variation in shear stress from the skin stress value above the bed to the stress value at the bed previously proposed for steady flow is extended here for the wave motion and verified by direct stress measurements. The calculations were carried out for mixed sand sediments with different grain size distributions including semiuniform and poorly sorted grains. Comparison with the available small- and large -scale data from flumes and oscillating tunnels yields agreement typically within plus/minus a factor two of measurements. [ABSTRACT FROM AUTHOR]

Rail corrugation that causes the vibration and the noise is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running. In the previous paper, we have already explained the growth mechanism and the wavelength determination mechanism of the rail corrugation from the dynamic point of view and verified their validity by comparing them with the field data. In this paper, we verify three influence factors of the elastically supported beam model left as subjects in the previous paper. As a result of analyses, it is confirmed that when the track structure is usually used type, the effect of the rail axial force on the growth mechanism of the rail corrugation and the error compared with the analysis results by the model of the moving coordinate system are negligible, and the analysis by the elastically supported beam model is valid including at near the anti-resonance frequency of the elastic support track system.

Composite laminates are usually made of anisotropic viscoelastic materials with layer-dependent properties. Although such structures are advantageous over the traditional single-material structure, their interfacial damage/failure is a great concern. In this paper, we present the general formulation and the corresponding solution to enhance our understanding on the guided waves in such laminates with imperfect interfaces. The formulation is based on the modified dual variable and position (DVP) method combined with a powerful and accurate root-finding algorithm. While the former overcomes the numerical instability when handling layered structures, the latter finds all the roots of the dispersion equation in a complex domain providing the full three-dimensional (3D) dispersion curves. After the proposed formulation is validated by the semi-analytical finite-element (SAFE) method for the perfect interface case, the present solution is applied to analyze the dispersion curves and mode shapes for a bilayer laminate with imperfect interface. Numerical examples demonstrate the detailed evolution mechanisms on wave features from perfect interface to complete delamination in the bilayer with imperfect interface. The results presented in this paper provide important insight to guide the in-situ monitoring of the evolution processes of the wave mode shapes and dispersion curves from perfect interface to complete delamination. [ABSTRACT FROM AUTHOR]

The equations of wave motion are considered in this article for three-layered medium which consists of liquid and porous layers with finite depth and solid half-space such as ocean bed. By virtue of scalar potential functions for each layer, complicated differential equations of layers are reduced to ordinary differential equations. An analytical method is applied to determine the Green's functions of media based on an arbitrary shaped time-harmonic excitation at the interface of liquid and porous layers. A Mathcad code is provided to compute the complex integrals. Displacement and stress fields of three layers are discussed. Comparing with special cases, existing answers represent the validity of the proposed method. Numerical results are carried out for circular patch, ring and point loads, and the effects of various parameters on the behavior of the system are plotted. Finally, the achieved results were under discussion. [ABSTRACT FROM AUTHOR]

The discrete element method has been widely adopted to study the phononic dispersion relation of granular crystals, but its intrinsic limitations in the conventional particle contact model are often overlooked. In this study, we numerically investigate both the quasi-static nonlinear behavior and the phononic dispersion relation of a pattern-transformable 2-D soft granular crystal using discrete element method (DEM) and finite element method (FEM). Regarding the quasi-static analysis at low strain levels, the DEM simulation results show good qualitative and quantitative agreement with the corresponding FEM results. However, our study reveals that the dispersion relations obtained by the stiffness matrix method coupled with DEM are substantially different from the corresponding FEM results. We find that independent rotational stiffness in the DEM contact models has little effect on the quasi-static motion and some lowest eigenmodes of dispersion relations, but it plays a pivotal role in the overall dispersion relation of granular crystals. Thus, we demonstrate that special care should be taken when DEM is adopted for calculating the phononic dispersion relation of soft granular crystals. [ABSTRACT FROM AUTHOR]

Wave propagation in a multi-layered transversely isotropic porous medium has been considered in this paper, which consists of n parallel layers overlying on a half-space. Potential functions are used to solve elastodynamic differential equations of the poroelastic medium. Time-harmonic excitation is assumed and the procedure of solution is performed in the frequency domain. Generalized reflection and transmission matrices are generated for compressional and shear waves separately. By means of the Hankel transformation method, coupled differential equations are altered to ordinary ones and Riemann surfaces are used to establish the path of integrations. A closed-form solution is described to reach Green's functions of displacements and stresses. Some special cases of excitations are discussed and verification of the solution is presented. The numerical results of a three-layered medium on a porous half-space are determined and discussed. [ABSTRACT FROM AUTHOR]

• Basic wave properties of deploying uniform pipes conveying fluid are elucidated. • A deploying phononic crystal (PC) pipe model is proposed based on the Bragg scattering mechanism. • Effects of the fluid excitation, deployment and component geometry on the band gaps of the system are achieved. • The study provides a theoretical base for the vibration suppression of deploying structures conveying fluid. Wave propagation and band gap (BG) characteristics of deploying long pipes conveying fluid are investigated based on a phononic crystal (PC) pipe model. The dispersion relation of the corresponding time-variant uniform pipe system is first derived in terms of the traveling wave feature of axially moving structures. Basic wave properties, such as the propagating and evanescent waves and the phase velocity and group velocity of propagating waves, are discussed to demonstrate the great effects of the flow velocity and deploying speed. The band structures of deploying pipe conveying fluid with periodic varying parameters are then investigated based on the Bragg scattering mechanism and treated by the transfer matrix method. A complex propagation constant is used to measure the band distribution. The fluid–structure interaction, deploying motion and component geometry are all found to have significant effects on the location and width of the BGs of the pipe. The deploying speed and flow velocity mainly influence the lower BGs while the component geometry acts much on the higher ones. [ABSTRACT FROM AUTHOR]

The coastline of the Gulf of Naples, Italy, is characterized by a series of infrastructures of strategic importance, including touristic and commercial ports between Pozzuoli to Sorrento, main roads, railways, and urban areas. Furthermore, the Gulf of Naples hosts an intense traffic of touristic and commercial maritime routes. The risk associated with extreme marine events is hence very significant over this marine and coastal area. On 28 December 2020, the Gulf of Naples was hit by an extreme sea storm, with severe consequences. This study focuses on the waterfront area of Via Partenope, where the waves overrun the roadway, causing massive damage on coastal seawall, road edges, and touristic structures (primarily restaurants). Based on the analysis of the meteorological evolution of the sea storm and its effects on the waterfront, we suggest that reflective processes induced on the sea waves by the tuff cliffs at the base of Castel dell’Ovo had an impact in enhancing the local-scale waves magnitude. This caused in turn severe flooding of the roadway and produced widespread damage along the coast. The analysis of the event of 28 December 2020, also suggests the need of an effective mitigation policy in the management of coastal issues induced by extreme sea storm events. Wind-based analysis and prediction of the sea wave conditions are currently discussed in the literature; however, critical information on wave height is often missing or not sufficient for reliable forecasting. In order to improve our ability to forecast the effects of sea storm events on the coastline, it is necessary to analyze all the components of the coastal wave system, including wave diffraction and reflection phenomena and the tidal change. Our results suggest in fact that only an integrated approach to the analysis of all the physical and anthropic components of coastal system may provide a correct base of information for the stakeholders to address coastal zone planning and protection.

Rail corrugation is such phenomenon that roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running, and cause the vibration and the noise. In the previous papers of ours, we have already explained the growth mechanism and the wavelength determination mechanism of the rail corrugation from the dynamic point of view and verified their validity by comparing them with the field data. In this paper, we report the results of simulation analyses of the characteristics of each step of formation, growth and saturation of the rail corrugation using a discrete elastic support model close to the actual track. As a result of the simulation, the following are confirmed : (1) at the formation step, by providing a minute and irregular wheel load fluctuation, rail surface roughnesses are formed with such wavelengths that their amplification factor of roughness amplitude is maximal and greater than 1.0. (2) at the growth step, as the contact length of the wheel / rail becomes longer, growth of roughness of the short wavelength is suppressed. (3) at the saturation step, when the roughness amplitude increases and the wheel loses the contact with the rail, the growth is suppressed and the roughness amplitude saturates. Based on these results, we present the progress process of the rail corrugation and the ways to approach the countermeasures.

Rail corrugation is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running, and causes the vibration and the noise. Therefore, in this paper, we analyze the amplification factor of roughness amplitude using a model that takes into consideration the interaction between the track and the vehicle, and clarify the growth mechanism and the wavelength determination mechanism of the rail corrugation. As a result of the theoretical analyses, it is indicated that the essential factors of growth of the corrugation are (1) interference of rail wave motion between the front and the rear wheels of a bogie of the vehicle, (2) anti-resonance phenomenon of the elastic support of the track system, (3) anti-resonance phenomenon of the total system of the track and the vehicle, and (4) anti-resonance phenomenon of the vehicle system. In addition, as a result of examing the rail corrugation measured on the commercial lines, it is confirmed that the causes of the corrugation occurrence are the above mentioned (1),(2) and (3) factors, and that the measured wavelengths almost agree with the theoretical values.