Search results for "Mathematica"

Time-dependent screening explains the ultrafast excitonic signal rise in 2D semiconductors

2020

We calculate the time evolution of the transient reflection signal in an MoS$_2$ monolayer on a SiO$_2$/Si substrate using first-principles out-of-equilibrium real-time methods. Our simulations provide a simple and intuitive physical picture for the delayed, yet ultrafast, evolution of the signal whose rise time depends on the excess energy of the pump laser: at laser energies above the A- and B-exciton, the pump pulse excites electrons and holes far away from the K valleys in the first Brillouin zone. Electron-phonon and hole-phonon scattering lead to a gradual relaxation of the carriers towards small $\textit{Active Excitonic Regions}$ around K, enhancing the dielectric screening. The acc…

Kompetencje przyszłych nauczycieli edukacji wczesnoszkolnej w zakresie konkretyzacji i abstrahowania jako determinanta poprawnego kształtowania pojęć…

2014

The skill of abstracting and concretizing as a det erminant of teacher’s competences in the sphere of forming mathematical notions in pupils of young…

2013

The person who shapes children’s attitudes towards the given subject and their manners of functioning within the mathematical space is the teacher of early education. Therefore, the latter should display a high standard of mathematical culture, as well as hold mathematical competences on a suitable level. Abstracting and concretizing are among the most important cognitive processes which are indispensable to form and develop mathematical notions. The paper is an attempt at answering the question whether prospective teachers of integrated education possess this vital-from the point of view of didactics-skill.

Climate and agriculture: empirical evidence for countries and agroecological zones of the Sahel

2022

International audience; ow heterogenous is the impact of climate change across space and the type of agricultural production? In this paper, we investigate the relationship between climate change and variability, measured by temperature and rainfall, and agricultural production at the country and agroecological zone levels of the Sahel. We consider a crop production index and five cereals (maize, millet, sorghum, wheat and rice). Based on an original climate database and an agricultural production function estimated for the period 1961–2016, we show that average rainfall and temperature during the growing season indeed have highly heterogeneous effects on agricultural production, depending …

Effects of the air density value on a wind generator electricity production capability

2016

The paper main issue is the evaluation of the influence of the air density value on the electricity production capability of a wind generator. Two different density air mathematical models, where the density has not a constant value, are here taken into account and compared in terms of reliability, accuracy and computational burden. Evaluations are carried out thanks to a horizontal axis wind generator full model built by the Authors in Matlab/Simulink environment. Simulation results are compared with real data.

Simulating multilevel dynamics of antimicrobial resistance in a membrane computing model

2019

Membrane computing is a bio-inspired computing paradigm whose devices are the so-called membrane systems or P systems. The P system designed in this work reproduces complex biological landscapes in the computer world. It uses nested “membrane-surrounded entities” able to divide, propagate, and die; to be transferred into other membranes; to exchange informative material according to flexible rules; and to mutate and be selected by external agents. This allows the exploration of hierarchical interactive dynamics resulting from the probabilistic interaction of genes (phenotypes), clones, species, hosts, environments, and antibiotic challenges. Our model facilitates analysis of several aspects…

Anemia management in end stage renal disease patients undergoing dialysis: a comprehensive approach through machine learning techniques and mathemati…

2016

Kidney impairment has global consequences in the organism homeostasis and a disorder like Chronic Kidney Disease (CKD) might eventually exacerbates into End Stage Renal Disease (ESRD) where a complete renal replacement therapy like dialysis is necessary. Dialysis partially reintegrates the blood ltration process; however, even when it is associated to a pharmacological therapy, this is not su fficient to completely replace the renal endocrine role and causes the development of common complications, like CKD secondary anemia (CKD-anemia) The availability of exogenous Erythropoiesis Stimulating Agents (ESA, synthetic molecules with similar structure and same mechanism of action as human eryth…

An Artificial Decision Maker for Comparing Reference Point Based Interactive Evolutionary Multiobjective Optimization Methods

2021

Comparing interactive evolutionary multiobjective optimization methods is controversial. The main difficulties come from features inherent to interactive solution processes involving real decision makers. The human can be replaced by an artificial decision maker (ADM) to evaluate methods quantitatively. We propose a new ADM to compare reference point based interactive evolutionary methods, where reference points are generated in different ways for the different phases of the solution process. In the learning phase, the ADM explores different parts of the objective space to gain insight about the problem and to identify a region of interest, which is studied more closely in the decision phas…

Parabolic equations with nonlinear singularities

2011

Abstract We show the existence of positive solutions u ∈ L 2 ( 0 , T ; H 0 1 ( Ω ) ) for nonlinear parabolic problems with singular lower order terms of the asymptote-type. More precisely, we shall consider both semilinear problems whose model is { u t − Δ u + u 1 − u = f ( x , t ) in Ω × ( 0 , T ) , u ( x , 0 ) = u 0 ( x ) in Ω , u ( x , t ) = 0 on ∂ Ω × ( 0 , T ) , and quasilinear problems having natural growth with respect to the gradient, whose model is { u t − Δ u + ∣ ∇ u ∣ 2 u γ = f ( x , t ) in Ω × ( 0 , T ) , u ( x , 0 ) = u 0 ( x ) in Ω , u ( x , t ) = 0 on ∂ Ω × ( 0 , T ) , with γ > 0 . Moreover, we prove a comparison principle and, as an application, we study the asymptotic behav…

Conceptual design and simulation of a water Cherenkov muon veto for the XENON1T experiment

2014

XENON is a direct detection dark matter project, consisting of a time projection chamber (TPC) that uses xenon in double phase as a sensitive detection medium. XENON100, located at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy, is one of the most sensitive experiments of its field. During the operation of XENON100, the design and construction of the next generation detector (of ton-scale mass) of the XENON project, XENON1T, is taking place. XENON1T is being installed at LNGS as well. It has the goal to reduce the background by two orders of magnitude compared to XENON100, aiming at a sensitivity of $2 \cdot 10^{-47} \mathrm{cm}^{\mathrm{2}}$ for a WIMP mass of 50 GeV/c$^{2}$. With…