Scientific papers (IF)

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https://dspace.rta.lv/handle/20.500.12169/21

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3D MATHEMATICAL MODEL CHARACTERIZING THE DYNAMICS OF THE TEMPERATURE FIELD OF A WALL STRUCTURE WITH A DOUBLE-SIDED FACING FROM A SAPROPEL-HEMP COMPOSITE MATERIAL
(2021)
Sharif E. Guseynov
;
Janis Rimshans
;
Jekaterina V. Aleksejeva
;
Aleksandrs Bereznojs
;
Pleikšnis, Staņislavs
In this paper, a 3D mathematical model is proposed to determine the dynamics of the temperature field in a three-layer composite sapropel-hemp slab. The proposed model consists of a system of three initial-boundary value problems with respect to the temperature function for each layer, respectively, and one initial-boundary value problem with respect to the unknown velocity of heat propagation along the thickness dimension of the composite sapropel-hemp slab.
3D SCANNERS. DIVERSITY AND OPERATING PRINCIPLES
(2017)
Aksjonovs, Artēmijs
;
Zaicevs, Edgars
;
Martinovs, Andris
The paper deals with existing 3D scanners classification and types. Each 3D scanner given the principle of operation. It examines the scope of application of different type scanners advantages and disadvantages. The aim was based on this data to create a 3D scanner prototype, by means of which an ordinary user can conveniently and easily scan a small, straightforward form objects.
A Meta-Model Based Approach to UML Modelling
(2008)
Teilāns, Artis
;
Arnis Kleins
;
Uldis Sukovskis
;
Yury Merkuryev
;
Ivars Meirans
This paper is devoted to a meta-model based approach to UML systems modelling. The approach allows creating a system model by operating with artefacts from the problem domain, followed by generation of a UML model. The discussed approach is illustrated by generating UML models, using Use Case and Activity diagrams of the UML language.
Scopus© Citations 5
A Metamodel Based Approach for UML Notated Domain Specific Modelling Language
(2011)
Arnis Kleins
;
Teilāns, Artis
;
Yuri Merkuryev
;
Ojars Krasts
This paper focuses on a metamodel based approach to Unified Modelling Language (UML systems modelling and simulation. The approach allows creating a system model by operating with artefacts from the problem domain. As a novelty for UML modelling, especially for simulation purposes, the presented meta-model is enriched by a set of stochastic attributes of modelled activities. Modelling process is ensured by developing UML based Domain Specific Language (DSL) that is suitable for the metamodel, where UML diagrams are complemented with attributes necessary for model simulation. A modelling tool prototype was developed with Microsoft Visual Studio using Microsoft Visualization and Modelling SDK. Elaborated models are stored in a modelbase which conforms to the described metamodel. Relevant DEVS simulation software will be developed for ability to run those models and analyse gathered results. The given approach facilitates increases of the productivity in development of domain specific modelling and simulation tools up to 10 times.
Scopus© Citations 2
A Method For Determination Of Specific Electrical Resistance Of Steel And Nano-Coating Sputtered On It
(2011)
Martinovs, Andris
;
Josef Timmerberg
;
Konstantins Savkovs
;
Aleksandrs Urbahs
;
Paul Beckmann
The paper describes methods developed to determine specific electrical conductivity and relative magnetic permeability of cylindrical steel items and nano-coatings deposited on them by sputtering. Research enables development of a new method for determination of thickness of vacuum deposited nano- coating that is based on application of skin effect.
A Multi-Model Approach for Simulation-Based Digital Twin in Resilient Services
(2021)
Arnis Lektauers
;
Jelena Pecerska
;
Vitalijs Bolsakovs
;
Andrejs Romanovs
;
Janis Grabis
;
Teilāns, Artis
Complex cyber-physical systems demand integrated solution approaches. The current work presents a multi-model approach for simulation-based digital twins as a formal and technological foundation for the analysis and improvement of resilient services. The given approach has several significant benefits including the possibility to conduct interactive simulations and experiments based on systems engineering principles, to share data across multiple data sources and storages, to manage operations in real-time, as well as to enable collaboration between the users in an integrated web platform. The proposal is illustrated on the use cases of secure telemedicine services and secure remote workplace.
Scopus© Citations 17
A Review of Methods for Reduction of Polycyclic Aromatic Hydrocarbons from Waste Water and Flue Gases
(2015-08-06)
Teirumnieks, Edmunds
;
I. Semjonova
This review describes methods which can be used for the reduction of the polycyclic aromatic hydrocarbon (PAH) emissions from wastewater and flue gases including principles of operation of the methods and studies of their effectiveness. There are discussed both methods, which nowadays are already used industrially, and their improvement opportunities as well as recent technological trends in this field. The methods have been classified into two main categories: flue gas treatment and wastewater treatment.
Scopus© Citations 1
A task for laser cutting of lamellae with TruLaser 1030
(2015)
Lyubomir Lazov
;
Hristina Deneva
;
Pavels Narica
The growing development of manufacturing, automotive, aerospace and other sectors in the industry generates the necessity to continuously expanding on modifications of electrical machinery and equipments which are used in them, as well as to improve their performance and reliability. The report presents some results from a study to the process of laser cutting through melting on lamellae for rotor and stator packages by using the laser system TruLaser 1030. Some functional dependencies are offered between physical quantities describing the cutting process by melting and technological parameters aimed providing the quality requirements. With a software TruTops to optimize the cutting out are shown the results of studies to determine the technological working time for cutting of a concrete stator lamella.
ADHESION TEST ON DIFFERENT WORK SURFACES
(2023)
Justs Batņa
;
Rihards Misjuns
;
Rēvalds, Ritvars
Šī publikācija parāda adhēzijas rezultātus, veicot to uz vairākām darba virsmām. Tika izmantotas 6 darba virsmas un veikti 18 adhēzijas testi, uz katras darba virsmas - 3 testi. Testu veikšanai uz darba virsmām tika printēti 20x20x10mm četrstūri no PETG plastmasas, izmantojot 3D printeri Ender 3 Pro. Adhēzijas testi veikti ar Zwick/Roell Z150 elektromehāniskās stiepes un kompresijas pārbaudes iekārtu.
AGING, FATIGUE AND DURABILITY OF RUBBER VIBRATION ISOLATION ELEMENTS
(2017)
Svetlana Polukoshko
;
Martinovs, Andris
;
Svetlana Sokolova
This paper deal with shock and vibration insulators, which usually are performed from the elastomeric (rubber-like) materials. Elastomeric materials give many engineering advantages due to their capability of absorbing input energy much better than engineering materials, high elasticity, good dynamic properties, low volume compressibility, a linear relationship between stress and strain up to strain of 15% ÷ 20%, resistance to aggressive environmental factors. Elastomeric materials are widely used in machine building, shipbuilding, civil engineering, aviation and aerospace as compensation devices, vibration dampers, shock absorbers. Laminated elastomers, consisting of interleaved thin layers of elastomer and rigid reinforcing layers are also successfully used as bearing, joints, dampers, compensating devices, shock-absorbers. Such structures have many advantages: ability to endure high stress (>200 MPa), ease of maintenance, non- necessity for lubrication, vibration and noise reduction, ability to work in a very dirty, dusty, abrasive environment. The disadvantage of elastomeric material are aging, i.e. changing its properties over time. In this paper the influence of aging of elastomeric materials on the damping properties of shock absorbers is considered based on the mechanical models of elastomers - Maxwell and Burgers modes. Fatigue endurance, i.e. the ability to withstand mechanical actions for a long time is studied based on experiments on dynamic shear with laminated rubber-metal structures. The experiments show that such structures have a very high fatigue life - up to 100 million cycles.
Scopus© Citations 5
Air ionizer and indoor plants interaction impact on ion concentration
(2017)
Natalija Siņicina
;
Martinovs, Andris
The plants emit different types of volatile organic compounds (Bio VOC’s) and can improve air quality: they effectively remove organic pollutions and reduce the number of microorganisms in the air by releasing phytoncides. The lack of negative ions in the air can cause deterioration of the health of humans breathing it. At the same time, an air saturated with negative ions can improve the state of health and provide a comfortable environment. In this article, the influence of the plants (Cupressus macrocarpa) on the number of ions is proved, based on a series of experiments performed with applying high-voltage pulses (air ionizer). This work is devoted to the elaboration of the mathematical relationship between the air ions concentration and the factors influencing it. For this purpose an experimental stand was made, consisting of two equal compartments: one contained the plants while another one was used as a control without plants. It was concluded that the plants, in general, are able to stabilize the ion concentration and to reduce its fluctuations. The plants help to increase the concentration of negative ions and to decrease the concentration of positive ones.
ALUMINUM AND STEEL WELDING WITH 500 W FIBRE LASER
(2023)
Raitis Dudenkovs
;
Lyubomir Lazov
The study of the process of laser welding of various aluminum-steel joints is necessary to promote the possibility of realization of new products and designs in instrumentation and mechanical engineering. Laser welding, due to its many advantages, is considered a very promising process of joining different materials, although its application in industry is still limited. Welding aluminum with steel using laser sources is a challenging task mainly due to the formation of brittle intermetallic joints (IMC) at the joint interface. This paper aims to give a brief overview of some new research on laser welding of aluminum to steel, as well as to point out some of our initial laboratory research in this direction.
Amount of Air Ions Depending on Indoor Plant Activity
(2015)
Natālija Siņicina
;
Andris Skromulis
;
Martinovs, Andris
Literature sources and earlier researches state that plants may be able to produce a variety of air ions, including negative light ions. In this article, the regularity of influence of plants on the number of ions in the room is being proved, basing on a series of experiments performed with the following plants: Spathiphyllum, Scindapsus, Strobilanthes, Chlorophytum and Pinus mugo. It was concluded that plants, in general, are able to stabilize the indoor ion concentration and reduce its fluctuations. The plants help to increase the concentrations of negative ions and decrease the concentration of positive ones, however the optimal and “healthy” ion concentration was not reached. Plants without artificial illumination work more as ion reducers, not producers.</span></p>
Scopus© Citations 5
ANALYSING THE INFLUENCE OF TECHNOLOGICAL PARAMETERS ON THE PROCESS OF LASER MARKING OF SURFACE OF ANODISED ALUMINIUM SAMPLES
(2023)
Ļubova Denisova
;
Antons, Pacejs
;
Emil Yankov
;
Lazov, Lyubomir
The requirements for marking in terms of contrast and durability are constantly increasing. In order to meet all these challenges, it is necessary to carry out research leading to the optimisation and increase in efficiency of the technological process of laser marking. In the case of aluminium, the contrast and durability of the marking depend on the values of the laser marking parameters. In order to determine the optimal laser marking method, experimental studies have been carried out, controlling the power, speed, frequency, pulse duration and line raster step for a specific anodised aluminium. The studies carried out were analysed and subsequently optimized to obtain a contrast marking. A Rofin PowerLine F 20 Varia fiber laser system and aluminium alloy 1050 with anodised surface were used for the research. The surface changes after the laser treatment were analysed using a laser scanning microscope and contrast determination method. The dependence of contrast and roughness on speed, power, frequency and raster step was analysed. Comparative plots of contrast and roughness variations versus laser marking technological parameters were constructed.
ANALYSIS AND EVALUATION OF FISCAL POLICY IN LATVIA
(2019)
Erika Zubule
;
Grabusts, Pēteris
The choice and topicality of the research topic is based on the fact that upon strengthening of the government's regulating role in economy, the notion of public finances positions itself, and state budget has become an important subject of both economic and political discussions as implementation of fiscal policy is takes place through it. In order to evaluate fiscal policy, it is necessary to evaluate the potential influence of different fiscal policy instruments on social and economic situation in the state. Aim of the research – to evaluate activities of fiscal policy implemented in Latvia in context of certain tax, namely, influence of corporate income tax on state's economic and financial indicators, identifying the main risks and imperfections of fiscal policy when ensuring state's budget. Applying simulation methods in the environment of Matlab/Simulink, the authors analyze and evaluate the influence of fiscal decisions and their implementation on the situation in Latvia, analyzing the most important tendencies in the sphere of corporate income tax payments according to the tax reform commenced in 2018.
ANALYSIS OF ARTIFICIAL INTELLIGENCE APPLICATIONS FOR AUTOMATED TESTING OF VIDEO GAMES
(2019)
Zarembo, Imants
Game testing is a software testing process for quality control in video games. Game environments, sometimes called levels or maps, are complex and interactive systems. These environments can include level geometry, interactive entities, player and non-player controllable characters etc. Depending on the number and complexity of levels, testing them by hand may take a considerable effort. This is especially true for video games with procedurally generated levels that are automatically created using a specifically designed algorithm. A single change in a procedural generation algorithm can alter all of the video game levels, and they will have to be retested to ensure they are still completable or meet any other requirements of the game. This task may be suitable for automation, in particular using Artificial Intelligence (AI). The goal of this paper is to explore the most promising and up-to-date research on AI applications for video game testing to serve as a reference for anyone starting in the field.
Scopus© Citations 8
ANALYSIS OF ASH CONTENT IN COMPOSITE BIOMASS FUELS
(2017)
Edgars Čubars
;
Poiša, Liena
The study reveals research of ash content in different composite biomass fuels. It contains analysis of samples obtained from various local Latvian biomass types, i.e. reed, wood, hemp, flax shives and peat, by combining them in different proportions. Ash is a by-product derived from combustion process consisting mostly of inorganic substances that are left after a fuel is burnt. High level of ash content in a fuel is undesirable because it causes problems in automation of biomass combustion process. Previous studies carried out by the author show that average ash content in reeds is 2%, which is a high index comparing with wood where ash content is approximately 0,5-1%. Thus, the high ash content in reeds my cause problems in reed combustion in solid fuel boilers. Besides, it is not possible to ensure permanent reed collection that would ensure continuous reed fuel generating process all year long. In order to reduce the ash content to the optimal level and to diversify raw materials necessary for biomass fuel generating process, the author suggests using composite fuels by combining different biomass types. The study contains optimal combining proportions of different biomass types for composite fuel production basing on the ash content in them.
Scopus© Citations 8
ANALYSIS OF COMPOSITE BIOMASS FUELS PROPERTIES
(2019)
Edgars Cubars
;
Poiša, Liena
There is a growing interest about the possibility of exploiting the local biomass as an energy source. The main resource for biofuel production in Latvia is wood. Water plants, like common reed, growing in nearly all of the water reservoirs in Latvia, and all cultivate plants and residues of cereal crops, also can be good alternative for solid bio fuels production. The aim of this paper is to analyze possibilities to make composite fuels from these recourses. The study reveals research of ash content and highest burning heat value in different composite biomass fuels. It contains analysis of samples obtained from various local Latvian biomass types, i.e. reed, wood, flax spray, hay, hemp and peat, by combining them in different proportions. The study contains optimal combining proportions of different biomass types for composite fuel production basing on the ash content and burning heat in them. The results of the study show that the value of wood highest burning heat is higher than another biomass types like reed, peat, hay, hemp and flax spray. It means that combining of different biomass types with wood, will reduce the calorific value of composite biomass. Also, wood is a fuel with a low ash content, and admixture of various biomass types available in Latvia, as well as admixture of coal dust to the wood in composite duels, increases ash content in the respective fuels. In order to increase the burning heat and decrease ash content value to the optimal level and to diversify raw materials necessary for biomass fuel generating process, the authors analyze possibilities of using composite fuels by combining wood and coal dust.
ANALYSIS OF CONTACTLESS RADIO FREQUENCY IDENTIFICATION TECHNOLOGIES AND ITS USAGE IN REZEKNE CITY INFRASTRUCTURE OBJECTS
(2016)
Zalužinskis, Artūrs
;
Zorins, Aleksejs
Author made the analysis of usage of contactless radio frequency identification technologies in Rezekne city infrastructure objects. Author provides the main types of radio frequency hardware, working principles and worldwide usage statistics. In the conclusion of the paper, author describes the further development opportunities of the radio frequency identification technologies.
Analysis of Fuzzy Time Series Forecasting for Migration Flows
(2022)
Oleg Uzhga-Rebrov
;
Grabusts, Pēteris
The goal of this article is to forecast migration flows in Latvia. In comparison with many other countries with sufficiently symmetric emigration and immigration flows, in Latvia, migration flows are very asymmetric: the number of emigrants considerably exceed the number of immigrants. Since statistical data about migration are usually inaccurate, we employ fuzzy time series forecasting methods for prognosticating migration flows in Latvia forecasting. The use of this type of method is often useful not only for forecasting purposes. Three different methods for fuzzy time series forecasting are used. A detailed comparative analysis of the obtained results is given. Generalized forecasts of the expected net migration flow in the future are presented.

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