Search results

The purpose of this paper is to analyze numerically the blowup in finite time of the solutions to a one-dimensional, bidirectional, nonlinear wave model equation for the propagation of small-amplitude waves in shallow water, as a function of the relaxation time, linear and nonlinear drift, power of the nonlinear advection flux, viscosity coefficient, viscous attenuation, and amplitude, smoothness and width of three types of initial conditions.

An implicit, first-order accurate in time, finite difference method valid for semipositive relaxation times has been used to solve the equation in a truncated domain for three different initial conditions, a first-order time derivative initially equal to zero and several constant wave speeds.

The numerical experiments show a very rapid transient from the initial conditions to the formation of a leading propagating wave, whose duration depends strongly on the shape, amplitude and width of the initial data as well as on the coefficients of the bidirectional equation. The blowup times for the triangular conditions have been found to be larger than those for the Gaussian ones, and the latter are larger than those for rectangular conditions, thus indicating that the blowup time decreases as the smoothness of the initial conditions decreases. The blowup time has also been found to decrease as the relaxation time, degree of nonlinearity, linear drift coefficient and amplitude of the initial conditions are increased, and as the width of the initial condition is decreased, but it increases as the viscosity coefficient is increased. No blowup has been observed for relaxation times smaller than one-hundredth, viscosity coefficients larger than ten-thousandths, quadratic and cubic nonlinearities, and initial Gaussian, triangular and rectangular conditions of unity amplitude.

The blowup of a one-dimensional, bidirectional equation that is a model for the propagation of waves in shallow water, longitudinal displacement in homogeneous viscoelastic bars, nerve conduction, nonlinear acoustics and heat transfer in very small devices and/or at very high transfer rates has been determined numerically as a function of the linear and nonlinear drift coefficients, power of the nonlinear drift, viscosity coefficient, viscous attenuation, and amplitude, smoothness and width of the initial conditions for nonzero relaxation times.

The purpose of this paper is to determine both analytically and numerically the solution to a new one-dimensional equation for the propagation of small-amplitude waves in shallow waters that accounts for linear and nonlinear drift, diffusive attenuation, viscosity and dispersion, its dependence on the initial conditions, and its linear stability.

An implicit, finite difference method valid for both parabolic and second-order hyperbolic equations has been used to solve the equation in a truncated domain for five different initial conditions, a nil initial first-order time derivative and relaxation times linearly proportional to the viscosity coefficient.

A fast transition that depends on the coefficient of the linear drift, the diffusive attenuation and the power of the nonlinear drift are found for initial conditions corresponding to the exact solution of the generalized regularized long-wave equation. For initial Gaussian, rectangular and triangular conditions, the wave’s amplitude and speed increase as both the amplitude and the width of these conditions increase and decrease, respectively; wide initial conditions evolve into a narrow leading traveling wave of the pulse type and a train of slower oscillatory secondary ones. For the same initial mass and amplitude, rectangular initial conditions result in larger amplitude and velocity waves of the pulse type than Gaussian and triangular ones. The wave’s kinetic, potential and stretching energies undergo large changes in an initial layer whose thickness is on the order of the diffusive attenuation coefficient.

A new, one-dimensional equation for the propagation of small-amplitude waves in shallow waters is proposed and studied analytically and numerically. The equation may also be used to study the displacement of porous media subject to seismic effects, the dispersion of sound in tunnels, the attenuation of sound because of viscosity and/or heat and mass diffusion, the dynamics of second-order, viscoelastic fluids, etc., by appropriate choices of the parameters that appear in it.

The purpose of this paper is to both determine the effects of the nonlinearity on the wave dynamics and assess the temporal and spatial accuracy of five finite difference methods for the solution of the inviscid generalized regularized long-wave (GRLW) equation subject to initial Gaussian conditions.

Two implicit second- and fourth-order accurate finite difference methods and three Runge-Kutta procedures are introduced. The methods employ a new dependent variable which contains the wave amplitude and its second-order spatial derivative. Numerical experiments are reported for several temporal and spatial step sizes in order to assess their accuracy and the preservation of the first two invariants of the inviscid GRLW equation as functions of the spatial and temporal orders of accuracy, and thus determine the conditions under which grid-independent results are obtained.

It has been found that the steepening of the wave increase as the nonlinearity exponent is increased and that the accuracy of the fourth-order Runge-Kutta method is comparable to that of a second-order implicit procedure for time steps smaller than 100th, and that only the fourth-order compact method is almost grid-independent if the time step is on the order of 1,000th and more than 5,000 grid points are used, because of the initial steepening of the initial profile, wave breakup and solitary wave propagation.

This is the first study where an accuracy assessment of wave breakup of the inviscid GRLW equation subject to initial Gaussian conditions is reported.

Refers to Montgomery and Fleeter (1996) who employed the finite‐analytic method of Chen et al. (1980) to study steady, two‐dimensional, inviscid, compressible, subsonic flow in a nozzle. Shows that, contrary to the statement made by Montgomery and Fleeter, their boundary conditions at the computational cell’s boundaries are not constructed from the particular solution to their equation (10). Deduces from a simple non‐linear second‐order ordinary differential equation that the finite or locally analytic method of Chen et al. (1980) only yields continuous but not differentiable solutions. Suggests a finite‐analytic method which provides continuous and differentiable solutions.

This paper aims to capture the effective behaviour of nonlinear coupled advection-diffusion-reaction systems and develop a new computational scheme based on differential quadrature method.

The developed scheme converts the coupled system into a system of ordinary differential equations. Finally, the obtained system is solved by a four-stage RK4 scheme.

The developed scheme helped to capture the different types of patterns of nonlinear time-dependent coupled advection-diffusion-reaction systems such as Brusselator model, Chemo-taxis model and linear model which are similar to the existing patterns of the models.

The originality lies in the fact that the developed scheme is new for coupled advection-diffusion-reaction systems such as Brusselator model, Chemo-taxis model and linear models. Second, the captured pattern is similar to the existing patterns of the models.

This study aims to examine the effect of the COVID-19 pandemic on the banking sector and to assess if COVID-19 was a trigger for the banking crisis.

To achieve the main objective, the beta of the banking sector was calculated and analysed. In addition, a fixed panel regression model was applied over the period from the 30th of December 2019 until the 24th of September 2021.

The results suggest that the pandemic contributed to higher volatility and risk in banking sector but did not confirm a systematic banking crisis.

This paper contributes to the literature by analysing the COVID-19 pandemic as a potential trigger for a banking crisis. This paper also contributed by studying the effects of COVID-19 on the banking sector, especially the risk in the banking sector.

This chapter describes an institutional choice that most Latin American countries have taken in the past 25 years: the creation of national Public Performance Monitoring and Evaluation (PPME) systems. We summarize research assessing their institutionalization, identify their shortcomings, and discuss trends demonstrating a potential – not yet realized – to fulfill their vocation as instruments of political and democratic accountability. Despite remarkable progress in their institutionalization, the evidence suggests that the systems fall short in producing strong results-oriented democratic accountability. Key factors hindering this aspiration include the systems' low credibility, problems associated to their diversification, low institutional coherence, and lack of effective coordination mechanisms to improve information legibility, its quality, its usefulness, and thus its use by both public managers and citizens. We suggest that PPME systems depend on environmental conditions beyond government structures and processes and argue that citizen-oriented mechanisms and entry points for social participation around the systems are required to fulfill their accountability function.

This study aims to analyze the impact of Artificial Intelligence (AI) and Machine Learning (ML) on heritage conservation and preservation, and to identify relevant future research trends, by applying scientometrics.

A total of 1,646 articles, published between 1985 and 2021, concerning research on the application of ML and AI in cultural heritage were collected from the Scopus database and analyzed using bibliometric methodologies.

The findings of this study have shown that although there is a very important increase in academic literature in relation to AI and ML, publications that specifically deal with these issues in relation to cultural heritage and its conservation and preservation are significantly limited.

This study enriches the academic outline by highlighting the limited literature in this context and therefore the need to advance the study of AI and ML as key elements that support heritage researchers and practitioners in conservation and preservation work.

The largest ever outbreak of Ebola virus disease (EVD), which began in December 2013, profoundly impacted not only the West African countries of Guinea, Sierra Leone, and Liberia, and to a lesser extent Nigeria, but also the rest of the world because some patients needed to be managed in high-resource countries. As of March 29, 2016, there were 28,616 confirmed, probable, and suspected cases of EVD reported in Guinea, Liberia, and Sierra Leone during the outbreak, with 11,310 deaths (case fatality rate of 39.5%). An unprecedented number of healthcare workers and professionals, including physicians, nurses, logistic and administrative personnel, housekeepers, epidemiologists, statisticians, psychologists, sociologists, and ethics experts in many countries, were directly or indirectly involved in the care of EVD patients.

The provision of medical care to critically ill EVD patients would have been challenging in any setting but was especially so in the remote and resource-limited areas where patients were stricken by EVD. Limited health personnel, medical supplies, and equipment, along with inadequate knowledge and skills for minimizing the risks of transmission to healthcare workers, could have led to the de-prioritization of patient care. However, ethical considerations demanded aggressive patient care (intensive care, dialysis, central vascular catheter indwelling, etc.) to produce positive outcomes without increasing the risks to healthcare workers and caregivers.

A major ethical consideration was that healthcare workers have a double obligation: while providing the best medical care to improve EVD patient survival, with symptom relief and palliation as required, they must also protect themselves and minimize further transmission to others, including their colleagues. During the 2014–2015 EVD epidemic, another ethical and clinical problem arose in relation to the management of healthcare workers deployed in Africa who acquired EVD while caring for infected patients. As of June 24, 2015, a total of 65 individuals had been evacuated or repatriated worldwide from the EVD-affected countries, of whom 38 individuals were evacuated or repatriated to Europe. The need for evacuation and repatriation, together with associated ethical issues, is discussed in this chapter.

This chapter reflects upon the trajectory of research in the geography of tourism in Spain. It begins with a review, including the evolution of the main topics present in the subdiscipline, with a special focus on developments since the 1990s. This is followed by an analysis of the current role and potential impact of academic tourism geography and a discussion on the recent growth in the publication of research results in international journals. Of importance are the institutional factors that explain the increasing recognition of research on the geography of tourism in Spain. Finally, the chapter discusses the hegemony of positivist approaches pivoting on land use, local and regional development, impact analysis, and landscape transformation, as well as the emerging links between Spanish tourism geography and the international mainstream schools of thought.