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1 – 10 of over 8000Shishir Gupta, Soumik Das and Rachaita Dutta
The purpose of the present study is to investigate the dispersion and damping behaviors of Love-type waves propagating in an irregular fluid-saturated fissured porous stratum…
Abstract
Purpose
The purpose of the present study is to investigate the dispersion and damping behaviors of Love-type waves propagating in an irregular fluid-saturated fissured porous stratum coated by a sandy layer.
Design/methodology/approach
Two cases are analyzed in this study. In case-I, the irregular fissured porous stratum is covered by a dry sandy layer, whereas in case-II, the sandy layer is considered to be viscous in nature. The method of separation of variables is incorporated in this study to acquire the displacement components of the considered media.
Findings
With the help of the suitable boundary conditions, the complex frequency relation is established in each case leading to two distinct equations. The real and imaginary parts of the complex frequency relation define the dispersion and attenuation properties of Love-type waves, respectively. Using the MATHEMATICA software, several graphical implementations are executed to illustrate the influence of the sandiness parameter, total porosity, volume fraction of fissures, fluctuation parameter, flatness parameters and ratio of widths of layers on the phase velocity and attenuation coefficient. Furthermore, comparison between the two cases is clearly framed through the variation of aforementioned parameters. Some particular cases in the presence and absence of irregular interfaces are also analyzed.
Originality/value
To the best of the authors' knowledge, although many articles regarding the surface wave propagation in different crustal layers have been published, the propagation of Love-type waves in a sandwiched fissured porous stratum with irregular boundaries is still undiscovered. Results accomplished in this analytical study can be employed in different practical areas, such as earthquake engineering, material science, carbon sequestration and seismology.
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Shalini Saha, Amares Chattopadhyay and Abhishek Kumar Singh
The purpose of this paper is to develop a numerical (finite-difference) model exploring phase and group velocities of SH-wave propagation in initially stressed transversely…
Abstract
Purpose
The purpose of this paper is to develop a numerical (finite-difference) model exploring phase and group velocities of SH-wave propagation in initially stressed transversely isotropic poroelastic multi-layered composite structures and initially stressed viscoelastic-dry-sandy multi-layered composite structures in two distinct cases.
Design/methodology/approach
With the aid of relevant constitutive relations, the non-vanishing equations of motions for the propagation SH-wave in the considered composite structures have been derived. Haskell matrix method and finite-difference scheme are adopted to deduce velocity equation for both the cases. Stability analysis for the adopted finite-difference scheme has been carried out and the expressions for phase as well as group velocity in terms of dispersion-parameter and stability-ratio have been deduced.
Findings
Velocity equations are derived for the propagation of SH-wave in both the composite structures. The obtained results are matched with the classical results for the case of double and triple-layered composite structure along with comparative analysis. Stability analysis have been carried out to develop expressions of phase as well as group velocity in terms of dispersion-parameter and stability-ratio. The effect of wavenumber, dispersion parameter along with initial-stress, porosity, sandiness, viscoelasticity, stability ratio, associated with the said composite structures on phase, damped and group velocities of SH-wave has been unveiled.
Originality/value
To the best of authors’ knowledge, numerical modelling and analysis of propagation characteristics of SH-wave in multi-layered initially stressed composite structures composed of transversely isotropic poroelastic materials and viscoelastic-dry-sandy materials remain unattempted inspite of its importance and relevance in many branches of science and engineering.
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– The purpose of this paper is to investigate the existence of SH-waves in fiber-reinforced layer placed over a heterogeneous elastic half-space.
Abstract
Purpose
The purpose of this paper is to investigate the existence of SH-waves in fiber-reinforced layer placed over a heterogeneous elastic half-space.
Design/methodology/approach
The heterogeneity of the elastic half-space is caused by the exponential variations of density and rigidity. As a special case when both the layers are homogeneous, the derived equation is in agreement with the general equation of Love wave.
Findings
Numerically, it is observed that the velocity of SH-waves decreases with the increase of heterogeneity and reinforced parameters. The dimensionless phase velocity of SH-waves increases with the decreases of dimensionless wave number and shown through figures.
Originality/value
In this work, SH-wave in a fiber-reinforced anisotropic medium overlying a heterogeneous gravitational half-space has been investigated analytically and numerically. The dispersion equation for the propagation of SH-waves has been observed in terms of Whittaker function and its derivative of second degree order. It has been observed that on the removal of heterogeneity of half-space, and reinforced parameters of the layer, the derived dispersion equation reduces to Love wave dispersion equation thereby validates the solution of the problem. The equation of propagation of Love wave in fiber-reinforced medium over a heterogeneous half-space given by relevant authors is also reduced from the obtained dispersion relation under the considered geometry.
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The purpose of this paper is to deal with the propagation of Love waves in inhomogeneous viscoelastic layer overlying a gravitational half-space. It has been observed velocity of…
Abstract
Purpose
The purpose of this paper is to deal with the propagation of Love waves in inhomogeneous viscoelastic layer overlying a gravitational half-space. It has been observed velocity of Love waves depends on viscosity, gravity, inhomogeneity and initial stress of the layer.
Design/methodology/approach
The dispersion relation for the Love wave in closed form is obtained with Whitaker’s function.
Findings
The effect of various non-dimensional inhomogeneity factors, gravity factor and internal friction on the non-dimensional Love wave velocity has been shown graphically. The authors observed that the dispersion curve of Love wave increases as the inhomogeneity factor increases. It is seen that increment in gravity, inhomogeneity and internal friction decreases the damping phase velocity of Love waves but it is more prominent in case of internal friction.
Originality/value
Surface plot of Love wave reveals that the velocity ratio increases with the increase of non-dimensional phase velocity and non-dimensional wave number. The above results may attract seismologists and geologists.
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A. Bouquet, C. Dedeban and S. Piperno
The use of the prominent finite difference time‐domain (FDTD) method for the time‐domain solution of electromagnetic wave propagation past devices with small geometrical details…
Abstract
Purpose
The use of the prominent finite difference time‐domain (FDTD) method for the time‐domain solution of electromagnetic wave propagation past devices with small geometrical details can require very fine grids and can lead to unmanageable computational time and storage. The purpose of this paper is to extend the analysis of a discontinuous Galerkin time‐domain (DGTD) method (able to handle possibly non‐conforming locally refined grids, based on portions of Cartesian grids) and investigate the use of perfectly matched layer regions and the coupling with a fictitious domain approach. The use of a DGTD method with a locally refined, non‐conforming mesh can help focusing on these small details. In this paper, the adaptation to the DGTD method of the fictitious domain approach initially developed for the FDTD is considered, in order to avoid the use of a volume mesh fitting the geometry near the details.
Design/methodology/approach
Based on a DGTD method, a fictitious domain approach is developed to deal with complex and small geometrical details.
Findings
The fictitious domain approach is a very interesting complement to the FDTD method, since it makes it possible to handle complex geometries. However, the fictitious domain approach requires small volume elements, thus making the use of the FDTD on wide, regular, fine grids often unmanageable. The DGTD method has the ability to handle easily locally refined grids and the paper shows it can be coupled to a fictitious domain approach.
Research limitations/implications
Although the stability and dispersion analysis of the DGTD method is complete, the theoretical analysis of the fictitious domain approach in the DGTD context is not. It is a subject of further investigation (which could provide important insights for potential improvements).
Originality/value
This is believed to be the first time a DGTD method is coupled with a fictitious domain approach.
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Yingli Li, Chenwei Wu, Yong Peng and Xudong Jiang
In order to investigate the vibration reduction properties of a three-dimensional elastic metastructure with spherical cavities at low frequencies.
Abstract
Purpose
In order to investigate the vibration reduction properties of a three-dimensional elastic metastructure with spherical cavities at low frequencies.
Design/methodology/approach
The bandgap characteristics of a three-dimensional elastic metastructure with spherical cavities are studied based on analytical and numerical approaches.
Findings
The results of both method revealed that the vibration of the vertexes masses is important for opening bandgaps. The fact that the big sphere cavity radius or short side length of the cube unit leads to a wider bandgap, is noteworthy.
Originality/value
This research provides theoretical guidance for realizing the vibration attenuation application of EMs in practical engineering.
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Using an extensive data set on Finnish workers during the years 1990–2002, we analyze the relation between dispersion of wages within plants and labor productivity. We find a…
Abstract
Using an extensive data set on Finnish workers during the years 1990–2002, we analyze the relation between dispersion of wages within plants and labor productivity. We find a positive and significant relation between dispersion of wages within plant and average sales per worker. This relation is quadratic when dispersion is conditioned on workers’ observable characteristics. We also find positive and significant relation between unconditional dispersion of wages within plant and value added per hours worked, while we find a non-significant relation between conditional wage dispersion and valued added per hours worked. Results indicate that the incentive effect of wage dispersion dominates fairness or sabotage considerations.
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Benoît Mahy, François Rycx and Mélanie Volral
– The purpose of this paper is to examine the impact of wage dispersion on sickness absenteeism observed in Belgian firms.
Abstract
Purpose
The purpose of this paper is to examine the impact of wage dispersion on sickness absenteeism observed in Belgian firms.
Design/methodology/approach
The authors use detailed linked employer-employee panel data for the period 1999-2006 that allow the authors to compute a conditional wage dispersion indicator following the Winter-Ebmer and Zweimüller (1999) methodology and to estimate the relationship between sickness absenteeism and wage dispersion while controlling for time-invariant workplace characteristics.
Findings
The authors find a positive and hump-shaped relationship between intra-firm wage dispersion and sickness absenteeism, the turning point of this relation being extremely high. In addition, the magnitude of the influence of wage dispersion on sickness absenteeism is found to be stronger in firms employing a larger share of blue-collar workers.
Practical implications
The results could therefore suggest that wage dispersion, suggestive of larger pay-for-performance mechanisms, decreases worker satisfaction and the workplace climate in general. Only a minority of workers, who are less sensitive to equity and cohesion considerations, would be less absent as pay-for-performance increases.
Originality/value
While numerous approaches analyse the link between wage dispersion and firm productivity, very few studies we are aware of are devoted to the relationship between wage dispersion and sickness absenteeism. Yet, the outcomes in terms of productivity and sickness absenteeism may be different. Furthermore, the influence of wage dispersion on sickness absenteeism does not seem unambiguous from a theoretical point of view. To the authors knowledge, it is the first time that this relation is analysed with Belgian data.
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L.J. Sluys, M. Cauvern and R. De Borst
The dispersive behaviour of waves in softening problems is analysed.Attention is focused on the influence of the numerical scheme on thedispersion characteristics in the process…
Abstract
The dispersive behaviour of waves in softening problems is analysed. Attention is focused on the influence of the numerical scheme on the dispersion characteristics in the process of localization of deformation. Distinction has been made between softening models defined in a standard plasticity framework and in a gradient‐dependent plasticity theory. Waves in a standard softening plasticity continuum do not disperse but due to spatial discretization dispersion is introduced which results in a mesh size dependent length scale effect. On the other hand, wave propagation in a gradient‐dependent softening plasticity continuum is dispersive. By carrying out the dispersion analysis on the discretized system the influence of numerical dispersion on material dispersion can be quantified which enables us to determine the accuracy for the solution of the localization zone. For a modelling with and without the inclusion of strain gradients accuracy considerations with respect to mass discretization, finite element size, time integration scheme and time step have been carried out.
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Juan Francisco Canal Domínguez and César Rodríguez Gutiérrez
This paper analyses the relationship between wage dispersion and firm size within a “two-tier” system of collective bargaining (firm bargaining and multi-employer bargaining…
Abstract
Purpose
This paper analyses the relationship between wage dispersion and firm size within a “two-tier” system of collective bargaining (firm bargaining and multi-employer bargaining levels). Collective bargaining has a decisive role in setting wages in Spain, and its regulation highly limits the possibility for smaller firms to negotiate their own collective agreement.
Design/methodology/approach
Based on the Spanish Structure of Earnings Survey 2006, 2010 and 2014, the authors use variance decomposition in order to deeply analyse the effect of bargaining level on wage dispersion and compare the value of each decile of the distribution of wages for the purposes of identifying the quantitative differences in wage compression.
Findings
In general, the outcomes positively linked firm size and firm bargaining to wage dispersion. However, if firm size is taken into account, the effect of firm bargaining is limited among small firm workers because this type of firm is not usually covered by firm bargaining. On the other hand, the time analysis allows observing a wage compression that follows different patterns depending on firm size, compressing the higher part of the distribution in case of small firms and the lower part in case of large firms. This should be explained by the fact that wage negotiation is dependent on firm size.
Social implications
Firm size has determined firm adjustment strategies to face the recent economic crisis and allows to evaluate the impact that changes in collective bargaining can have on wage distribution
Originality/value
There is no research that has tried to analyse the relationship between wage dispersion and firm size in a context where collective bargaining is essential to understand the wage structure. Normally, firm size plays a decisive role in wage policy given that the capacity of a company to negotiate an agreement is closely linked to its size.
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