Search results for "Online"
showing 10 items of 4526 documents
An existence and uniqueness principle for a nonlinear version of the Lebowitz-Rubinow model with infinite maximum cycle length
2017
The present article deals with existence and uniqueness results for a nonlinear evolution initial-boundary value problem, which originates in an age-structured cell population model introduced by Lebowitz and Rubinow (1974) describing the growth of a cell population. Cells of this population are distinguished by age a and cycle length l. In our framework, daughter and mother cells are related by a general reproduction rule that covers all known biological ones. In this paper, the cycle length l is allowed to be infinite. This hypothesis introduces some mathematical difficulties. We consider both local and nonlocal boundary conditions.
Theoretical study of Fe doping and oxidation–reduction influence on the photorefractive effect in BaTiO_3
1993
We numerically solve charge-transport and Poisson equations for photorefractive BaTiO3 single crystals with a band model, using four impurity levels, Fe2+–Fe3+, Fe3+–Fe4+, VO••–VO•, and VO•-VOx. Densities and photoinduced spatial distributions of each population are computed as a function of annealing O partial pressure. Space-charge field and beam-coupling gain are also computed as a function of annealing O partial pressure, temperature, Fe concentration, grating wave vector, and light intensity. We discuss the intervening mechanism of impurity centers and the correlations between experimental conditions of crystal growth, oxidation–reduction treatments, and measurement parameters.
Set Membership (In) Validation of nonlinear positive models for biological systems
2006
The complexity of biology needs quantitative tools in order to support and validate biologists intuition and traditional qualitative descriptions. In this paper, Nonlinear Positive models with constraints for biological systems are validated/invalidated in a worst-case deterministic setting. These models are usefull for the analysis of the DNA and RNA evolution and for the description of the population dynamics of viruses and bacteria. The conditional central estimate and the Uncertainty Intervals are determined in order to validate/invalidate the model. The effectiveness of the proposed procedure has been illustrated by means of simulation experiments.
On the qualitative analysis of the solutions of a mathematical model of social dynamics
2006
Abstract This work deals with a family of dynamical systems which were introduced in [M.L. Bertotti, M. Delitala, From discrete kinetic and stochastic game theory to modelling complex systems in applied sciences, Math. Models Methods Appl. Sci. 7 (2004) 1061–1084], modelling the evolution of a population of interacting individuals, distinguished by their social state. The existence of certain uniform distribution equilibria is proved and the asymptotic trend is investigated.
I suffer from a serious rare disease : a challenge to sing and choreograph on TikTok
2021
Este artículo se encuentra disponible en la siguiente URL: https://revista.profesionaldelainformacion.com/index.php/EPI/article/view/86449 Este artículo pertenece al número "Interacción y visualización ". Las enfermedades raras son patologías muy severas y discapacitantes que afectan al 7% de la población mundial. Para intentar visibilizar y denunciar su situación, las personas que padecen estas enfermedades y sus familias hallaron en Facebook, Twitter y YouTube, entre otras redes sociales, un canal eficaz para compartir sus problemas, exigir una mayor inversión en investigación y poder conllevar sus dificultades diarias. Desde entonces, se han estimado como válidos elementos simbólicos y d…
The Tax Justice Network-Africa v Cabinet Secretary for National Treasury & 2 Others: A Big Win for Tax Justice Activism?
2019
This paper develops an optimization model for selecting a large subsample that improves the representativeness of a simple random sample previously obtained from a population larger than the population of interest. The problem formulation involves convex mixed-integer nonlinear programming (convex MINLP) and is therefore NP-hard. However, the solution is found by maximizing the “constant of proportionality” – in other words, maximizing the size of the subsample taken from a stratified random sample with proportional allocation – and restricting it to a p-value high enough to achieve a good fit to the population of interest using Pearson’s chi-square goodness-of-fit test. The beauty of the m…
Identification of Replicator Mutator models
2006
The complexity of biology literally calls for quantitative tools in order to support and validate biologists intuition and traditional qualitative descriptions. In this paper, the Replicator-Mutator models for Evolutionary Dynamics are validated/invalidated in a worst-case deterministic setting. These models analyze the DNA and RNA evolution or describe the population dynamics of viruses and bacteria. We identify the Fitness and the Replication Probability parameters of a genetic sequences, subject to a set of stringent constraints to have physical meaning and to guarantee positiveness. The conditional central estimate is determined in order to validate/invalidate the model. The effectivene…
ON THE EXISTENCE OF LIMIT CYCLES IN OPINION FORMATION PROCESSES UNDER TIME PERIODIC INFLUENCE OF PERSUADERS
2008
This paper concerns a model of opinion formation in a population of interacting individuals under the influence of external leaders or persuaders, which act in a time periodic fashion. The model is formulated within a general framework inspired to a discrete generalized kinetic approach, which has been developed in Ref. 6. It is expressed by a system of non-autonomous nonlinear ordinary differential equations. The dynamics of such a system is investigated and the existence of a globally asymptotically stable periodic solution is analytically proved in three example cases, each one corresponding to a different quantitative choice of the actions of the persuaders. Equivalently, in three part…
Impact of Nonlinear Inductor on Efficiency and Power Losses in a SMPS: a Case Study
2022
This paper proposes a comparative analysis focused on losses in two Switched Mode Power Supplies, adopting a linear inductor and an inductor operated up to saturation, respectively. The use of the nonlinear inductor saves weight and cost on the magnetic material, which is of great interest for automotive applications; however, it increases the peak current and can increase losses. The analysis aims to compare, by simulations, the impact on the efficiency of the different current waveforms throughout the converter. The losses are discussed in detail and calculated for each component of the converters.
Las publicaciones en línea: su regulación legal
2015
Breve análisis de la regulación legal de las publicaciones en soporte no tangible que efectúa el Real Decreto núm. 63/2015 de 10 de julio, por el que se regula el depósito legal de las publicaciones en línea.