Scientific papers (IF)

Permanent URI for this collection

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

Browse

Now showing 1 - 20 of 259

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 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 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
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.
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 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.
ANALYSIS OF LASER PROCESSING OF ARTIFICIAL LEATHER
(2019)
Pāvels Narica
;
Ruta Laizāne
;
Antons, Pacejs
;
Mežinska, Silvija
With the development of laser technologies, the field of application of lasers is developing as well. They are capable of processing numerous materials and are still finding their application in unexpected areas. In this case, lasers are studied as a system with which black and white color artificial leather can be processed. This modern material allows you to combine comfort, practicality and reasonable price in a finished product. The manufacturer of artificial leather provides wide possibilities of design. In this study laser beam was used for dark and light laser markings on black and white color artificial leather and in this work, it could be observed how CO2 and fiber laser processing influence this specific material.
Scopus© Citations 1
ANALYSIS OF THE SIMULATED ANNEALING METHOD IN CLASSIC BOLTZMANN MACHINES
(2016-12-10)
Grabusts, Pēteris
The paper analyses a model of a neural net proposed by Hinton et al (1985). They have added noise to a Hopfield net and have called it Boltzmann machine (BM) drawing an analogy with the behaviour of physical systems with noises. The concept of simulated annealing is analysed. The experiment aimed at testing the state of thermal equilibrium for a Boltzmann net with three neurons, specified threshold values and weights at two different temperatures, T=1 and T=0,25, is described.
Analyze of Leachate Composition in the Dumpsites of East-Latgale Region
(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.
Antibacterial and anti-viral effects of silver nanoparticles in medicine against COVID-19—a review
(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).
Scopus© Citations 25
Apple and Pear Scab Expert System
(2023)
Apeināns, Ilmārs
;
Zarembo, Imants
;
Lācis, Gunārs
;
Litavniece, Lienīte
Plant disease, such as apple and pear scab, control is a crucial issue of fruit-growing. Apple and pear are among the most widely grown (approximately 43% of all fruit tree area) and economically important fruit crops worldwide and in Latvia. Research projects have produced research data covering various aspects of plant-pathogen interactions, but there is no internal linkage analysis, as well as implementation of other types of data (such as environmental and meteorological data, etc.). Establishing such a data integration system would allow the identification of new regularities in plant-pathogen interactions, and provide mechanisms for disease control decisions. In this study an expert system was developed aimed to help professional fruit-growers evaluate the possible impact of apple and pear scab to the plant health and yield quality. The expert system is based on a previously developed apple and pear scab ontology and consists of a web based front-end and triplestore back-end.
APPLE AND PEAR SCAB ONTOLOGY
(2021)
Zarembo, Imants
;
Teilāns, Artis
;
Toms Bartulsons
;
Olga Sokolova
;
Lienīte Litavniece
;
Anna Nikolajeva
An important issue in horticulture is ensuring plant disease, such as scab, prevention and treatment. Apple and pear are among the most widely grown (approximately 43% of all fruit tree area [1]) and economically important fruit crops specified worldwide and in Latvia. Scab diseases caused by ascomycetous fungi Venturia inaequalis and V.pyrina are economically the most important diseases worldwide. Research projects have produced research data covering various aspects of plant-pathogen interactions, but there is no internal linkage analysis, as well as implementation of other types of data (such as environmental and meteorological data, etc.). Establishing such a data integration system would allow the identification of new regularities in plant-pathogen interactions, and provide mechanisms for disease control decisions. Semantic analysis is one of information technology approaches to finding relationships in data. The product of analysis is ontology. There are plant disease ontologies which provide classification of diseases and describe their reasons. However, there is no ontology which describes a specific plant and relations among its farming parameters and disease probability. Such an ontology for apple and pear scab is presented in this paper. The constructed ontology can be applied to develop guidelines or digital expert systems.
Scopus© Citations 1
Apple Scab Detection in the Early Stage of Disease Using a Convolutional Neural Network
(2022)
Kodors, Sergejs
;
Gunārs Lācis
;
Inga Moročko-Bičevska
;
Zarembo, Imants
;
Olga Sokolova
;
Toms Bartulsons
;
Apeināns, Ilmārs
;
Vitālijs Žukovs
Modern reviews of challenges related to deep learning application in agriculture mention restricted access to open datasets with high-resolution natural images taken in field conditions. Therefore, artificial intelligence solutions trained on these datasets containing low-resolution images and disease symptoms in the advanced stage are not suitable for early detection of plant diseases. The study aims to train a convolutional neural network for apple scab detection in an early stage of disease development. In this study a dataset was collected and used to develop a convolutional neural network based on the sliding-window method. The convolutional neural network was trained using the transfer-learning approach and MobileNetV2 architecture tuned on for embedded devices. The quality analysis in laboratory conditions showed the following accuracy results: F1 score 0.96 and Cohen’s kappa 0.94; and the occlusion maps — correct classification features.
Scopus© Citations 1

Browse

Browsing Scientific papers (IF) by Department "Faculty of Engineering"

Results Per Page

Sort Options