Analele Universității ”Dunărea de Jos” din Galați. Fascicula II, Matematică, fizică, mecanică teoretică / Annals of the ”Dunarea de Jos” University of Galati. Fascicle II, Mathematics, Physics, Theoretical Mechanics

Summary

* * * — Mon, 16 Sep 2024 00:00:00 +0300

Cuprins

Characterization of flavonoids: an explorative review

Cristina (Paraschiv) Nedelcu, Steluța Gosav, Mirela Praisler — Mon, 16 Sep 2024 00:00:00 +0300

Flavonoids represent a significant dietary resource for humans. Due to their diverse molecular structures, unique bifunctionalities, minimal side effects and rich pharmacological profiles, flavonoids have become valuable targets for drug design. The objective of this paper is to conduct a systematic review of the various types of flavonoids and their physico-chemical properties.

The use of interpolation polynomials in the approximation of functions: comparative study

Stefanut Ciochina — Mon, 16 Sep 2024 00:00:00 +0300

In this study, we present three methods for approximating functions using interpolation polynomials. In engineering, there are many situations where it is necessary to approximate the value of a function at a certain point, knowing only a finite set of experimental data or when the function itself is presented in a form that is not easily usable. We use specific methods in numerical analysis such as Lagrange interpolation, the method of dividing differences and Neville’s method. Given a function f defined on an interval [a,b], the purpose of this work is to construct a function that approximates the function f at a predetermined value. The expression of the approximation functions will be calculated and we will evaluate the obtained error for each approximation.

The content, dynamics and migration of As in the Prut River during the 2020-2023 years

Petru Ciorba — Mon, 16 Sep 2024 00:00:00 +0300

Arsenic is an immunotoxic element that can be found in living organisms, being a part of many important biochemical processes. It interacts with different groups of proteins, lipids and, in increased quantities, affects oxidative processes. As a toxic element, arsenic concentrations are limited in drinking water and food products by Community Directives and national regulations. From2020 to2023, we investigated the dynamics of this element in the water and suspended matter from the Prut River ecosystems within the Republic of Moldova. The sources of pollution with arsenic compounds are various pesticides, herbicides, metallurgical enterprises and power plants that use fossil coal and fuel oil. The pollution with pharmaceutical preparations that contain arsenic compounds should also be mentioned. Arsenic compounds enter the body of animals and humans in increased quantities primarily through polluted air, especially in industrial areas near thermal power plants and facilities such as metallurgical, military, chemical and pharmaceutical plants, as well as through drinking and mineral water, grapes, fruits, seafood (fish, snails, algae), medicines, pesticides and herbicides. The risk of arsenic accumulation is also increased in tobacco smokers.

Vegetal layer restoration of contaminated sites from petroleum industry using sewage sludge

Mon, 16 Sep 2024 00:00:00 +0300

Soil is a non-renewable natural resource, extremely valuable for maintaining life on Earth. Large areas of soil are often polluted with petroleum products as a result of various human activities. In this case, it is necessary to remediate the contaminated soils from the oil industry and return them to the natural and economic circuit. In addition, large quantities of sewage sludge are generated daily by sewage treatment plants. The purpose of this study was to use the soil subjected to a bioremediation experiment with sewage sludge as support for the development of a new vegetal layer to restore the natural balance. The grass was sown in the land, which had previously been treated with sewage to monitor its development. Through microbiological analysis, we observed that soil and sewage sludge mixtures have a high content of heterotrophic bacteria and filamentous fungi that could play an important role in seed germination. IR (infrared spectroscopy) analysis revealed a decrease in hydrocarbon concentrations in the petroleum- contaminated soil treated with sewage sludge. By using the combined methods SEM-EDX (scanning electron microscopy – energy dispersive X-ray), we also analyzed the soil microstructure and the distribution of chemical elements to highlight the plants' evolution. The present study considers soil regeneration in areas contaminated with petroleum products and opens new perspectives for the use of sewage sludge in the ecological reconstruction of petroleum-contaminated sites.

Algorithms for pollutants forecasting

Corina Dima — Mon, 16 Sep 2024 00:00:00 +0300

The impact of pollution on human health is very well known and affects more and more economic and social activities. Since the authorities do not always have the necessary equipment and trained personnel for pollution monitoring, we observed the need to develop algorithms for approximating different polluting values. This paper is a review of the main algorithmic approaches to estimate pollutant values. Most of the proposed approaches are based on machine learning, neural networks and decision trees.

Algorithmic approach to the finite element approximation method

Nina N. Cazacu — Mon, 16 Sep 2024 00:00:00 +0300

The paper provides a general method for obtaining the so-called “shape functions”, which approximate the solution of systems of differential equations with boundary conditions. Unlike classic methods usually used for solving variational problems, the presented procedure approximates the unknown functions with piecewise linear functions, using a sequence of C++ code. The domain in which the system is defined is divided into finite elements, and the nodal values of the solution are obtained by solving the Fermat system associated with the specific boundary conditions of the defined domain. The proposed algorithm, based on C++ code, is designed to solve problems in two-dimensional cases or higher.