High order schemes for reaction-diffusion singularly perturbed systems

In this paper we are interested in solving e¿ciently a singularly per-turbed linear system of di¿erential equations of reaction-di¿usion type. Firstly, anon–monotone ¿nite di¿erence scheme of HODIE type is constructed on a Shishkinmesh. The previous method is modi¿ed at the transition points such that an inversemonotone scheme is obtained. We prove that if the di¿usion parameters are equal itis a third order uniformly convergent method. If the di¿usion parameters are di¿er-ent some numerical evidence is presented to suggest that an uniformly convergentscheme of order greater than two is obtained. Nevertheless, the uniform errors arebigger and the orders of uniform convergence are less than in the case correspondingto equal di¿usion parameters

An almost third order finite difference scheme for singularly perturbed reaction–diffusion systems

AbstractThis paper addresses the numerical approximation of solutions to coupled systems of singularly perturbed reaction–diffusion problems. In particular a hybrid finite difference scheme of HODIE type is constructed on a piecewise uniform Shishkin mesh. It is proved that the numerical scheme satisfies a discrete maximum principle and also that it is third order (except for a logarithmic factor) uniformly convergent, even for the case in which the diffusion parameter associated with each equation of the system has a different order of magnitude. Numerical examples supporting the theory are given

Early Investigation of a Landslide Sliding Surface by HVSR and VES Geophysical Techniques Combined, a Case Study in Guarumales (Ecuador)

[EN] The access road to the powerhouse's hydraulic system's facilities in Guarumales (Azuay, Ecuador) presents a medium-sized landslide. Geophysical tests were conducted in the initial research stage, combining electrical and seismic methods. A vertical electrical sounding (VES) and horizontal to vertical spectral ratio (HVSR) survey campaign have been taken as a reference for the analysis of the landslide area. The distribution of these test points has been at three different levels along the landslide where the access road crosses it, trying to cover the area¿s most extensive possible length and width. In the area, we find the geology dominated by the presence of schists, altered to different degrees and presenting blocks of material with a lower degree of alteration within colluvium formed by a clayey matrix and coarse material of the exact nature. There is also observed runoff water and groundwater in the area. The results obtained through SEV tests have allowed for defining the separation zone of the mobilized or sliding materials compared to the fixed or immobile ones (potentially, the sliding surface was marked). Using the HVSR technique, the natural vibration frequencies of the ground associated with the sliding mass (separation of seismic impedances between a two-layer model: mobile and fixed) have been determined. Previous authors proposed an empirical relationship establishing the exponential relationship, already proposed by previous authors, between sediment thickness and natural frequencies. It has been possible to determine the depth of the position of the loosely compacted sediment zone (and probably moving or mobilized) compared to that of compact materials (immobile) and thereby define the potential rupture surface.Alonso-Pandavenes, O.; Torrijo, F.; Garzón-Roca, J.; Gracia, A. (2023). Early Investigation of a Landslide Sliding Surface by HVSR and VES Geophysical Techniques Combined, a Case Study in Guarumales (Ecuador). Applied Sciences. 13(2). https://doi.org/10.3390/app1302102313

Misalignment and tilt effect on aspheric intraocular lens designs after a corneal refractive surgery

Purpose: To numerically evaluate and compare the tolerance to misalignment and tilt of aspheric intraocular lenses (IOLs) designed for three eyes: with standard cornea and with simulated corneas after myopic and hyperopic laser ablation surgery. Methods: Three aspheric IOLs of +20.00 diopter (D) with different spherical aberration (SA) (Z04) values have been designed using a theoretical model eye. Drastic changes on the theoretical eye anterior corneal asphericity have been performed to simulate myopic and hyperopic refractive surgeries. The effect of IOL misalignment and tilt on the image quality has been evaluated using a commercial optical software design for the three eye models. Image quality was assessed from the modulation transfer function (MTF), root mean square (RMS) values of defocus, astigmatism, coma and spherical aberration (Z04), and retinal images obtained from a visual simulator using an aleatory optotype of 0.00 LogMar visual acuity (VA). Results: IOL misalignment and tilt reduced MTF values in general, and increased wavefront aberrations errors. Aberration-free IOLs maintained best the MTF values when misalignments were applied, together with good on-axis optical quality. IOLs with negative SA (Z04) correction decreased the MTF value under 0.43 for misalignments values higher than 0.50 mm with the three corneas. The effect of misalignment on RMS astigmatism and coma was correlated with the IOL SA (Z04) and with the three corneas. Conclusions: This theoretical study shows that the largest degradation in image quality arises for the IOL with the highest amount of spherical aberration (Z04). Moreover, it has been found that the aspherical design has a more influential role in misalignment tolerance than in tilt tolerance

Microanálisis comparado de la transición demográfica en tres islas de las Azores, siglos XVIII-XX: Diferencias en el pasado, semejanzas en el presente

The demographic transition is a global phenomenon. However, previous studies have demonstrated the existence of differences in its development between areas that are in close proximity. The aim of this article is to compare the process of demographic transition in the rural communities of three islands in the archipelago of the Azores (Pico, Flores and Corvo) using life course data for more than 250 years. Throughout the article several variables related to nuptiality, fertility, mortality and mobility have been analysed. Our results show clear differences between communities prior to the demographic transition and, to a lesser extent, during the demographic transition process. The island of Flores, for instance, has historically presented higher fertility because of a lower age at marriage. The island of Pico, on the other hand, had a lower fertility level, higher age at marriage and longer birth intervals. During the demographic transition, infant mortality first began to fall in Flores, therefore increasing population pressure. Since 1840, international migration and the abandonment of children served as mechanism to reduce the population pressure. © 2021 Universidad de Murcia. All rights reserved.nities of three islands in the archipelago of the Azores (Pico, Flores and Corvo) using life course data for more than 250 years. Throughout the article several variables related to nuptiality, fertility, mortality and mobility have been analysed. Our results show clear differences between communities prior to the demographic transition and, to a lesser extent, during the demographic transition process.The island of Flores, for instance, has historically presented higher fertility because of a lower age at marriage. The island of Pico, on the other hand, had a lower fertility level, higher age at marriage and longer birth intervals. During the demographic transition, infant mortality first began to fall in Flores, therefore increasing population pressure. Since 1840, international migration and the abandonment of children served as mechanism to reduce the population pressure

Polypharmacy in older adults with human immunodeficiency virus infection compared with the general population

Background: The percentage of older HIV-positive patients is growing, with an increase in age-related comorbidities and concomitant medication. Objectives: To quantify polypharmacy and profile types of non-antiretroviral drugs collected at community pharmacies in 2014 by HIV-positive individuals on antiretroviral therapy and to compare these findings with those of the general population. Methods: HIV-positive patients (n=199) were compared with a group of patients from the general population (n=8, 172), aged between 50 and 64 years. The factors compared were prevalence of polypharmacy (=5 comedications with cumulative defined daily dose DDD] per drug over 180), percentage of patients who collected each therapeutic class of drug, and median duration for each drug class (based on DDD). Results were stratified by sex. Results: Polypharmacy was more common in HIV-positive males than in the male general population (8.9% vs 4.4%, P=0.010). Polypharmacy was also higher in HIV-positive females than in the female general population (11.3% vs 3.4%, P=0.002). Percentage of HIV-positive patients receiving analgesics, anti-infectives, gastrointestinal drugs, central nervous system (CNS) agents, and respiratory drugs was higher than in the general population, with significant differences between male populations. No differences were observed in proportion of patients receiving cardiovascular drugs. The estimated number of treatment days (median DDDs) were higher in HIV-positive males than in males from the general population for anti-infectives (32.2 vs 20.0, P<0.001) and CNS agents (238.7 vs 120.0, P=0.002). A higher percentage of HIV-positive males than males from the general population received sulfonamides (17.1% vs 1.5%, P, 0.001), macrolides (37.1% vs 24.9%, P=0.020), and quinolones (34.3% vs 21.2%, P=0.009). Conclusion: Polypharmacy is more common in HIV-positive older males and females than in similarly aged members of the general population. HIV-positive patients received more CNS drugs and anti-infectives, specifically sulfonamides, macrolides, and quinolones, but there were no differences in the percentage of patients receiving cardiovascular drugs. It is essential to investigate nonantiretroviral therapy medication use in the HIV-positive population to ensure these patients receive appropriate management

Deformation Quantization of Fermi Fields

Deformation quantization for any Grassmann scalar free field is described via the Weyl-Wigner-Moyal formalism. The Stratonovich-Weyl quantizer, the Moyal $\star$-product and the Wigner functional are obtained by extending the formalism proposed recently in [35] to the fermionic systems of infinite number of degrees of freedom. In particular, this formalism is applied to quantize the Dirac free field. It is observed that the use of suitable oscillator variables facilitates considerably the procedure. The Stratonovich-Weyl quantizer, the Moyal $\star$-product, the Wigner functional, the normal ordering operator, and finally, the Dirac propagator have been found with the use of these variables.Comment: 19+1 pages, no figures, revtex4 file styl

Prediction of Horizontal Daily Global Solar irradiation using artificial neural networks (ANNs) in the Castile and Leon Region, Spain

The next day's global horizontal solar irradiation is predicted using artificial neural networks (ANNs) for its application in agricultural science and technology. The time series of eight−years data is measured in an agrometeorological station, which belongs to the SIAR irrigation system (Agroclimatic Information System for Irrigation, in Spanish), located in Mansilla Mayor (León, Castile and León region, Spain). The zone has a Csb climate classification (i.e., Mediterranean Warm Summer Climate), according to Koppen−Geiger. The data for the years (2004−2010) are used for ANNs training and the 2011 as the validation year. ANN models were designed and evaluated with different numbers of inputs and neurons in the hidden layer. A neuron was used in the output layer, for all models, where the simulation of global solar irradiation for the next day on the horizontal surface results. Evaluated values of the input data were the horizontal daily global irradiation of the current day [H(t)] and two days before [H(t−1), H(t−2)], the day of the year [J(t)], and the daily clearness index [Kt(t)]. Validated results showed that best adjustment models are the ANN 7 model (RMSE = 3.76 MJ/(m2 ·d), with two inputs [H(t), Kt(t)] and four neurons in the hidden layer) and the ANN 4 model (RMSE = 3.75 MJ/(m2 ·d), with two inputs [H(t), J(t)] and two neurons in the hidden layer). Thus, the studied ANN models had better results compared to classic methods (CENSOLAR typical year, weighted moving mean, linear regression, Fourier and Markov analysis) and are practically easier as they need less input variable

Prediction of horizontal daily global solar irradiation using artificial neural networks (ANNs) in the Castile and León Region, Spain

This article evaluates horizontal daily global solar irradiation predictive modelling using artificial neural networks (ANNs) for its application in agricultural sciences and technologies. An eight year data series (i.e., training networks period between 2004–2010, with 2011 as the validation year) was measured at an agrometeorological station located in Castile and León, Spain, owned by the irrigation advisory system SIAR. ANN models were designed and evaluated with different neuron numbers in the input and hidden layers. The only neuron used in the outlet layer was the global solar irradiation simulated the day after. Evaluated values of the input data were the horizontal daily global irradiation of the current day [H(t)] and two days before [H(t−1), H(t−2)], the day of the year [J(t)], and the daily clearness index [Kt(t)]. Validated results showed that best adjustment models are the ANN 7 model (RMSE = 3.76 MJ/(m2·d), with two inputs ([H(t), Kt(t)]) and four neurons in the hidden layer) and the ANN 4 model (RMSE = 3.75 MJ/(m2·d), with two inputs ([H(t), J(t)]) and two neurons in the hidden layer). Thus, the studied ANN models had better results compared to classic methods (CENSOLAR typical year, weighted moving mean, linear regression, Fourier and Markov analysis) and are practically easier as they need less input variables