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Now showing 1 - 20 of 779
  • Publication
    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.
  • Publication
    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.
  • Publication
    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
  • Publication
    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
  • Publication
    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.
  • Publication
    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
  • Publication
    A multidimensional approach to support training activities in the digital era
    (2020)
    Gilberto Marzano
    ;
    Svetlana Usca
    ;
    Velta Lubkina
    The digital revolution is producing changes that require continuous learning interventions. Accordingly, there is an increasing demand for lifelong learning that requires new teaching–learning approaches applicable to a large number of learners. A transformative learning is argued to be a powerful approach to tackle the online learning issues, providing trainees with the opportunity to learn, confront, engage, reflect and explore new learning modalities. In this paper, we present an ongoing research aimed to employ online learning for different student needs. It has been carried out within the scope of an applied research project, DocTDLL. We illustrate the multidimensional approach that has been developed to support the online training activities of Ph.D. students, integrating both the transformative learning and social learning paradigms. We also report the data that emerged from a survey conducted in Latvia on a sample of 260 people to explore the attitudes and expectations regarding digital learning.
  • Publication
    A NEW INNOVATIVE PRODUCT PORTFOLIO IN LATVIA AND ITS AVAILABILITY ON THE MARKET (BUSINESS INCUBATION PROGRAMME 2009-2014)
    (2016)
    Liene Amantova-Salmane
    ;
    Maris Igavens
    ;
    Irena Silinevica
    New product development is a very important issue for economic growth and welfare growth in general. The support programme of business incubators plays a significant role for operation of start-up companies in their creation of new products. In spite of it many enterprises of business incubators are not able to finish their innovation process, which shows on necessity to research  these problems. The aim of the research is to investigate the portfolio of new products which were developed by Latvian Start-up companies in the frame of the Business Incubation Programme  2009-2014,  related to  commercialization and market uptake.  The research is based on the authors’ conducted research as a part of scientific grant of Rezekne Academy of Technologies „New product development process modeling and analysis in Latvia – innovation barriers”.  The following methods are used in this research: content analysis, deductive, logical and comparison, and word cloud methods. As a result, the authors worked out and offered the word cloud of innovative products, which are produced in business incubators in Latvia, and which are available in markets.  The authors  worked out the word cloud of New Products, which are produced in business incubators, but are not on the markets.
  • Publication
    A NEW PARADIGM OF SUSTAINABLE DEVELOPMENT DIMENSIONS
    (2018)
    Liene Amantova-Salmane
    Sustainable development has become an universal phrase and the area of many policy initiatives, especially those regarding environmental organizations. The revision of the dimensions of sustainable development gives vital support to develop and implement indicators for them. The dimensions of sustainable development are inseparable and mutually reinforcing. Sustainable development actions depend on complexity and working with different interests of environment and development. It is impossible to predict what needs future generations will have. The obligation of the current generation is both to use and protect the world resources in ways that meet human development opportunities more justifiably today, but which do not exclude choices for such actions tomorrow. The aim of the research is to analyse the dimensions of sustainable development. More deeply, the research tasks are to outline the hierarchical organization of sustainable development criteria and indicators and to create a new paradigm of sustainable development dimensions. The methods of research are monographic, quantitative, deductive, and inductive. The key result: a new paradigm of sustainable development dimensions is created. Sustainable development is a concept, possibly surrounding closely every aspect of human society. The meaning of the dimensions of sustainable development is all the time in progress. There is a new approach to the dimensions given in the research. Sustainability could be understood better in terms of “here and now”, “later” and “elsewhere”. The existence of sustainability criteria guarantees sustainability in the long perspective. It can be suggested that the sustainability criteria analysis and their practical use could be further developed.
  • Publication
    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
  • Publication
    A Review of Telerehabilitation Solutions for Balance Disorders
    (2017-02-08)
    Velta Lubkina
    ;
    Gilberto Marzano
    In the last few years, there has been an increase in telerehabilitation research that shows a large variability in terms of technical solutions, methodological approaches, intervention protocols, and outcome measures. This paper provides an overview of the current literature on telerehabilitation solutions for balance disorders.
    Scopus© Citations 7
  • Publication
    A STUDY OF LOCAL ARTISAN AND CRAFTSMAN MARKET OPERATION IN REZEKNE
    (2017)
    Maris Igavens
    ;
    Daina Znotina
    Local food, both from the perspective of the producer and the consumer, is becoming all the more popular topic in modern society. One of the places where the buyers and sellers of these products meet is the market. The research aim is to study the operation of local artisan and craftsman markets in Rezekne and the opportunities for improving their operation. The theoretical and practical aspects of artisan activity are described in the study; surveys have been conducted to find out the opinions of market visitors on the supply of the artisan market; data analysis and interpretation; and to make conclusions and suggestions for improving the operation of the local artisan and craftsman market in Rezekne. Research methods: logical construction, analysis, a survey, the graphical method.  The study results in a conclusion that the buyers of the local artisan and craftsman market in Rezekne are satisfied with the supply; however there are opportunities for its improvement. The main aspects with the opportunities for improvement are: spreading information about the market, i.e. its advertisement, expanding the assortment offered, extending the opening hours of the market, expanding the premises and the parking space of the market.
  • Publication
    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.
  • Publication
    ACCOUNTING AND ECONOMIC ANALYSIS IN CONDITIONS OF DIGITALIZATION AND GLOBALIZATION OF PUBLIC RELATIONS
    (2019)
    Iryna Yegorova
    ;
    Yaroslav Izmaylov
    ;
    Evalds Viskers
    The aim of the research is to identify the directions of accounting and economic analysis in the context of globalization and electronic data processing. The role of accounting and economic analysis in managing sustainable development of the national economy and economic entities is determined. The theoretical and methodological design of improved systems of accounting and economic analysis of  enterprises’ economic activity including expanded and updated functions, tasks and principles in accordance with current conditions of digitalization and globalization of public relations is presented. It allows creating appropriate organizational and methodological provision of accounting and analytical support of managing enterprises’ activity to increase reliability and relevance of accounting information. The authors prove that  improved components of the accounting and economic analysis system of enterprises’ economic activity in the conditions of digitalization and globalization of economic relations will enhance application of  accounting techniques, procedures, methodological support, management and internal control.
  • Publication
    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.
  • Person
    Adijāns, Imants
    PhD student
  • Publication
    ADULT LEARNING AND SOCIALIZATION PROCESSES: RTA EXPERIENCE
    (2020-06-16)
    Velta Lubkina
    ;
    Gatis Stafeckis
    ERASMUS+ Strategic Partnership project Adult Self-Learning: Supporting Autonomy in a Technology-Mediated Environment/ ASL (Ref. No. 2019-1-TR01-KA204-076875) co-funded by the Erasmus+ programme, Key Action 2: Cooperation for innovation and the exchange of good practices – Strategic Partnerships for adult education. The project aims at teaching learners to acquire new skills and competences using learning innovative practices and digital technologies as well as developing a functioning collaborative learning environment to help them identify skills gaps and needs and to collaborate locally and independently for joint capacity-building. The ASL project is expected to produce three main results corresponding to three primary European priorities:1. Supporting the setting up of, and access to, up skilling pathways (priority: adult lifelong learning);2. Improving and extending the supply of high quality learning opportunities tailored to the needs of individual low-skilled or low-qualified adults (priority: social inclusion/further education opportunities);3. Open education and innovative practices in a digital era (priority: adults' professionalization/empowerment).
  • Publication
    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
  • Publication
    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.
  • Publication
    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.