92 documents found, page 1 of 10

Reminiscências sobre Rafael Sasportes (1960-2024)

Nota biográfica sobre Rafael Sasportes publicada na secção "Testemunhos" da revista Ad Astra.

A matemática na sociedade europeia e a Sociedade Europeia de Matemática

Apresenta-se uma brevíssima panorâmica do surgimento e desenvolvimento da Matemática no espaço europeu, bem como uma breve referência às organizações científicas (academias e sociedades) relevantes para as ciências matemáticas na Europa, terminando com uma secção sobre a fundação e as atividades da Sociedade Europeia de Matemática (EMS), incluindo reminiscências sobre o papel da Sociedade Portuguesa de Matemáti...

The discrete generalized exchange-driven system

We study a discrete model for generalized exchange-driven growth in which the particle exchanged between two clusters is not limited to be of size one. This set of models include as special cases the usual exchange-driven growth system and the coagulation-fragmentation system with binary fragmentation. Under reasonable general condition on the rate coefficients we establish the existence of admissible solutions...

Differential equations and applications

Texto utilizado na lecionação da disciplina homónima lecionada pelo autor no German-Mongolian Institute for Resources and Technology, Nalaikh, Ulaanbaatar, Mongolia, em setembro de 2024.

Mathematics and online education

Theoretical analysis of a discrete population balance model with sum kernel

The Oort–Hulst–Safronov equation is a relevant population balance model. Its discrete form, developed by Pavel Dubovski, is the main focus of our analysis. The existence and density conservation are established for nonnegative symmetric coagulation rates satisfying V_{i;j} \leq i + j , \forall i, j \in N. Differentiability of the solutions is investigated for kernels with V_{i;j} \leq i^\apha + j^\alpha˛ where ...

The continuous Redner–Ben-Avraham–Kahng coagulation system: well-posedness and ...

This paper examines the existence of solutions to the continuous Redner-Ben-Avraham-Kahng coagulation system under specific growth conditions on unbounded coagulation kernels at infinity. Moreover, questions related to uniqueness and continuous dependence on the data are also addressed under additional restrictions. Finally, the large-time behaviour of solutions is also investigated.

Mathematical models of chiral symmetry-breaking: a review of general theories, ...

We review the literature surrounding chiral symmetry-breaking in chemical systems, with a focus on understanding the mathematical models underlying these chemical processes. We comment in particular on the toy model of Sandars, Viedma’s crystal grinding systems and the APED model. We include a few new results based on asymptotic analysis of the APED system.

Modelling silicosis: dynamics of a model with piecewise constant rate coefficients

We study the dynamics about equilibria of an infinite dimensional system of ordinary differential equations of coagulation–fragmentation–death type that was introduced recently by da Costa et al. (Eur J Appl Math 31(6):950–967, 2020) as a model for the silicosis disease mechanism. For a class of piecewise constant rate coefficients an appropriate change of variables allows for the appearance of a closed finite ...

Mathematical investigations of a kinetic model for glycerol hydrogenolysis via ...

In this paper we report on some mathematical investigations of the chemical process for the hydrogenolysis of glycerol over a heterogeneous metal catalyst. The main interest of this process is related to the fact that glycerol is produced as a by-product in the production of biodiesel in huge amounts that are expected to exceed the projected demands. This makes the sustainability of biodiesel production depend ...