mathematical modeling

Математичні моделі управління портфелями проектів з удосконалення системи безпеки життєдіяльності

Наведено типові математичні моделі управління портфелями проектів з удоско- налення системи безпеки життєдіяльності (БЖД), сутність яких полягає у виборі такої оптимальної структури заходів, реалізація яких значно впливає на її ефективність за умови обмеженого обсягу виділених ресурсів для окремо взятої території чи їх групи, а також регіону загалом. Встановлено, що отримані результати числового експерименту в багатьох випадках не тільки збігаються з результатами реального розподілу фінансових ресурсів, але й у багатьох випадках є значно кращими від них.

Mathematical modeling of frequency-controlled electric drive with dual-winding induction machine considering spatial harmonics

Mathematical modeling of frequency-controlled dual-winding induction electric drives typically involves using mathematical circuit models to investigate transient and steady-state modes. Such models often disregard spatial harmonics. Spatial harmonics in machines refer to the harmonics of the distribution of the winding function within the machine stator slots. Mathematical models based on the method of finite element analysis are primarily used to study the influence of spatial harmonics on the stator current and electromagnetic torque of dual-winding machines.

Mathematical modeling of changes in density of near-surface ionic layers in semi-infinite metals. Equations for displacements of ionic layers

In this work, we propose a mathematical model for describing the change in the ion density of the near-surface ionic layers of a semi-infinite metal.  Through averaging over the subsystem of conduction electrons, we obtain in the adiabatic approximation an effective Hamiltonian of the ionic subsystem of a semi-infinite metal, which models the effect of the "metal–vacuum" separation surface on the structure of the near-surface ionic layers.  We calculate the free energy of such a model and, by its minimization, obtain an equation for finding the displacements $\mathbf{\x

Mathematical modelling of flux-cored layer formation

Mathematical model for the calculation of the chemical composition of deposited metal with sufficient accuracy has been developed. The presented mathematical model has been developed taking into account shares of base and clad metal, the metal of the previous roll in the subsequent one, and the relative step of cladding.

Wave processes in the constructions of mechanisms and buildings

In the article a methodology for researching wave processes in weakly nonlinear homogeneous one-dimensional systems – elements of machine and building structures is proposed. It is based on D'Alembert's method  of constructing solutions of wave equations and the asymptotic method of nonlinear mechanics. Resonant and non-resonant cases are considered. In the non-resonant case, the influence of viscoelastic forces and small periodic disturbances on the oscillatory process is taken into account.

Control of mathematical modeling process of dynamics of harmful substances concentrations on the basis of ontological approach

The problem of building a mathematical model of the dynamics of nitrogen dioxide concentrations at different parts of the city is considered in the paper. The peculiarities of the construction of such models on the basis of periodic measurement of concentrations of harmful substances and identification on the basis of the measurements obtained are considered.

Study of two species prey–predator model in imprecise environment with harvesting scenario

This study proposes and explores a prey–predator model that presents a functional response to group behavior of prey–predator harvesting.  We study a non-linear model of prey–predator growths in two species.  The proposed model is supported by theoretical and numerical results.  Some numerical descriptions are provided to help our analytical and theoretical conclusions.  For all possible parameter values occurring in a prey–predator system, we solved it by using both VIM (variational iteration method) and HPM (homotopy perturbation method).  We also used MATLAB coding to compare our approxi

Mathematical Modeling of Transition Processes in the High Voltage Transmission Line in Short Circuit Modes

The article analyzes the publications, which shows that two approaches to the analysis of transients in long power lines with distributed parameters are popular today: based on simplified methods of solving the equation of a long line, or equivalent to the known equation of a long line by circuit substitution schemes. In applying the first approach, the authors do not take into account the running resistance, phase and interphase conductivities, calculating the usually mentioned processes by the known methods of D’Alembert and “wandering waves”.

Mathematical modeling of Leptospirosis spread in Malaysia

Leptospirosis is a zoonotic disease that is caused by the pathogen Leptospira, and it can spread indirectly or directly from infected animals to humans.  According to the official statistics from the Malaysian Ministry of Health, leptospirosis outbreaks appeared to be in the most critical condition in the recent few years.  The Susceptible--Infected--Recovered compartmental model and its extensions have been applied widely in disease modeling.  This paper aims to present a compartmental model for leptospirosis spread in Malaysia.  Using this approach, an epidemiological model is formulated

Mathematical Modeling of Transients Processes in Three-phase Transmission Line in Two-phase Short Circuit Mode

The article analyzes scientific publications, which showed that for most part of the study transients processes in the long power lines with distributed parameters is carried out by equivalent to the known equation of a long line with distributed parameters by a circular equivalent, or solve this equation using simplified approaches. These approaches require deterministic boundary conditions to the long line equation, which is not always possible when modeling transients processes in electrical networks.