Teirumnieks, Edmunds

2021, Lazov, Lyubomir, Nikolay Angelov, Teirumnieks, Edmunds

Today, methods for marking parts and components in industrial production are constantly improving, and they must meet several basic criteria for active traceability by consumers. The parameter that is of paramount importance for the quality of the marking is related to the contrast of the marked sign or QR code. To achieve optimal contrast, a number of technological factors and the functional relationships between them must be taken into account.The report examines the role of the number of repetitions on contrast in raster marking of HS6-5-2-5 tool steel products. The dependences of the number of repetitions on the speed and frequency are also taken into account - the main factors in the process of laser ablation. Graphs of the depth of the marking are drawn depending on the number of repetitions and the linear density of the pulses. The experiments were made with a fiber laser. By the performed analyses the working intervals of processing between the studied factors are deduced, allowing to achieve the desired optimal result.

2021, Lazov, Lyubomir, N Angelov, Teirumnieks, Edmunds, I Draganov, A Lengerov, A Atanasov, I Balchev

This work makes use of the finite element model, whose results are validated by experiments. The effect is discussed of the speed on the laser marking process. Numerical experiments are performed to determine the temperature fields produced by laser pulses on samples of aluminum, a material with wide industrial uses. The numerical calculations are performed for the cases of a fiber laser and a CuBr laser. Plots are drawn of the temperature dependence on the speed for two power densities for both lasers. Preliminary working speed intervals are determined for the power densities used.

2020, Teirumnieks, Edmunds, Ivaylo Balchev, Risham Singh Ghalot, Lazov, Lyubomir

The article reviews the research on disinfecting the air through air filters and ventilation systems using silver nanoparticles (Ag NPs) (encouraged from the present situation of COVID-19) focusing on stopping the spreading of deadly viruses. The primary goal of the research is to demonstrate possible antiviral Ag NP formulations to be delivered by inhalation, to minimize the worsening of respiratory system infections. The basic design of the study includes a bibliometric analysis of the study of the effect of Ag NPs on the disinfection of viral infections. The research will discuss the idea of the use of laser ablation with Ag NPs for antiviral and antibacterial effects. The research article results in compelling evidence for the use of Ag NPs for medicinal purposes for infectious diseases/viruses and will contribute to the progress of medical science to protect healthcare workers from dangerous viruses at medical institutions. Practically, the research will generate a sterile system, which might be employed by every public or private institution economically with Ag NPs (because of their antimicrobial properties).

2017, Andris Skromulis, Juris Breidaks, Teirumnieks, Edmunds

In the article, the possible impact of atmospheric pollution on air ions of various classes were analysed by the method of statistical analysis. The raw data summarized and analysed in the article were obtained within one year period in a monitoring station, by measuring CO, NO, NO2, SO2, O3, PM10, temperature, relative humidity, wind speed and direction, as well as spectrum of air ion concentrations, where ion size varied between 0.75 to 36.6 nm. With a help of stepwise regression, the significant parameters were selected and mathematic equations were obtained in order to explain concentrations of positive and negative small, intermediate and heavy air ions with the selected parameters.

2015, Janis Prols, Teirumnieka, Ērika, Teirumnieks, Edmunds

Iron concentrations, distribution and migration forms, depending on pH and oxidation – reduction potential, were analyzed in case of the Kemeri-Jaunkemeri occurrence (area about 240 km2) of sulphide containing water (maximal sulphides concentration – 74 mg/l), located in Latvia. Iron content was investigated in 457 wells located within all area of occurrence. Those wells were installed to two aquifers: the Quarternary multi-aquifer and Salaspils aquifer, where occurrence of sulphide containing groundwater is distributed. All groundwater of occurrence is classified in four types depending on oxygen, sulphides and organic matter content in the groundwater.  Modeling of groundwater migration forms was carried out, and it is stated that iron migrates basically as Fe2 in oxygen and suphides non-containing water. Migration forms are influenced by concentration of organic matter in the aquifer. The portion of Fe2 migrating in a form of free decreases due to formation of complexes with fulvic and humic acids, which can reach 36.5% of all migration forms. Iron migrates as Fe(OH)3  in oxygen containing water (more than 99% of determined forms). Presence of iron is ascertained also in sulphides containing water, where iron migrates basically as (98.8% of determined forms).  This occurs due to formation of complexes with sulphydes – FeHS- and Fe(HS)2o.

2019, Lazov, Lyubomir, Nikolay Angelov, Teirumnieks, Edmunds, Teirumnieka, Ērika

Studying the impact of speed on a number of laser processes such as marking, engraving, cutting, welding and others is crucial for the optimization of these technological processes. The processing speed, along with the frequency of laser pulses and their duration, also determines the time of action in the processing area and hence the absorbed quantity of electromagnetic energy. Based on numerical experiments with specialized software TEMPERATURFELD3D, the report analyzes the temperature variation in the processing area as a function of speed. The researches were analyzed for processing with two types of lasers emitting in the visible and infrared areas of the electromagnetic spectrum and two types of steels (tool and structural). From the course of the obtained temperature fields the dependence of temperature on the speed at two power densities was obtained. The obtained results help to make a preliminary assessment the speed work intervals for the processes as laser marking, laser engraving, laser cutting, laser welding and others. In this way, it is assisted in building an optimal concept for the passing of a particular technological process in function of the laser source, the material and the type of the technological operation.

2023, Petar Tsvyatkov, Emil Yankov, Lazov, Lyubomir, Teirumnieks, Edmunds, Teirumnieka, Ērika

Marking of metal products is essential in many industrial processes. It is mandatory for the finished products according to regulations of the European and world legislation. Traditional marking usually creates contrasting symbols that can easily be erased and forged.In recent years, a new method for product identification has appeared - color marking. One of the advantages of this method is that it is difficult to counterfeit. This article aims to present the progress of color marking technology on two types of materials. Three groups of factors have been analyzed: the laser source; the technological process; material properties. Their role in obtaining a specific color marking on Ti and AISI 304 is shown. The results are presented in tables. Each color can be repeated only with strict observance of the three groups of factors.

2021, Teirumnieka, Ērika, Dagnija Blumberga, Teirumnieks, Edmunds

Global trends in the world are currently representing a serious incentive to bring ‘green thinking’ to life. This is the case of replacing synthetic materials derived from fossil resources with natural-origin, renewable resources. In the automotive industry and other segments of the manufacturing industry, increasing attention is being paid to the use of natural fibers in the manufacturing of composite materials. For example, flax and hemp fiber, as reinforcing material, is starting to widely replace carbon fiber. It is not just an ecological benefit, but also an important product protecting human health, since the amount of emissions that pollute the environment is minimized. Consequently, that lead to reduced intake by human being of harmful substances that would affect its health status. Existing composite materials used in motor vehicles, produced from carbon fibers, are creating very sharp fracture areas in the event of accidents causing human injury, while materials from natural fiber plants in this case are free from sharp edges at the place of fracture. Raw materials derived from hemp processing are used in the automotive, textile industry, construction (hemp concrete, heat insulation material), energy, biofuel production, arts and design, paper production, food, medicine, etc. This paper covers the main types of products derived from hemp.

2021, Kangro, Ilmārs, Harijs Kalis, Teirumnieks, Edmunds, Teirumnieka, Ērika

In this paper we consider the conservative averaging method (CAM) with special spline approximation for solving the non-stationary 3-D mass transfer problem. The special hyperbolic type spline, which interpolates the middle integral values of piece-wise smooth function is used. With the help of these splines the initial-boundary value problem (IBVP) of mathematical physics in 3-D domain with respect to one coordinate is reduced to problems for system of equations in 2-D domain. This procedure allows reduce also the 2-D problem to a 1-D problem and thus the solution of the approximated problem can be obtained analytically. The accuracy of the approximated solution for the special 1-D IBVP is compared with the exact solution of the studied problem obtained with the Fourier series method. The numerical solution is compared with the spline solution. The above-mentioned method has extensive physical applications, related to mass and heat transfer problems in 3-D domains.

2003, Teirumnieks, Edmunds, Teirumnieka, Ērika

There are are 28 working or closed but not recultivated municipal solid waste dumpsites in East-Latgale now. A number of these dumpsites are situated near lakes, rivers, in old mineral quarries etc [3, 6]. All these dumpsites pollute groundwater, soil and present danger for human health. One of the dangerous factors is leachate which is generated in these dumpsites and which pollutes groundwate, soil and drinking water. The analysis of leachate sample chemical content in the biggest East-Latgale dumpsites “Ritini”, “Zvirgzdene”, “Zelceva” and “Mostovaja” has been done in 2002. The content of leachate depends on content of waste, dumpsite management etc. The most polluted leachate is in the biggest dumpsites of region – “Ritini” and “Zvirgzdene”. These are city dumpsites (Rezekne and Ludza). Significantly less polluted leachate is found in the dumpsites “Zelceva” and “Mostovaja”. This is valid for all analyzed parameters – COD, conductivity, Ntot., NH4 + and Cl.