Scientific papers (IF)

Permanent URI for this collection

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

Browse

Browsing Scientific papers (IF) by Issue Date

Filter results by year or month
Now showing 1 - 20 of 398
  • Publication
    DAŽI DIELEKTRISKĀS CAURLAIDĪBAS PĒTĪJUMU ASPEKTI GUMIJAS MĀKSLĪGĀS NOVECOŠANAS PROCESOS
    (1999)
    Martinovs, Andris 
    Gumija ekspluatācijas laikā ir pakļauta ilgstošai dabiskai novecošanai, kuras rezultātā izmainās gumijas struktūra, pasliktinās elastīgās īpašības un mehāniskā izturība. Konstruktoram ir nepieciešams zināt, cik ilgi konkrētais gumijas izstrādājums dotajos apstākļos spēs kalpot. To var prognozēt uz paātrināto eksperimentu pamata. Šie eksperimenti ir saistīti ar gumijas mākslīgo novecošanu, kad pētāmajam paraugam papildus tiek pievadīta enerģija, iedarbojoties uz to ar temperatūras lauku, radiāciju, ķīmiski aktīvām vielām, vibrācijām vai kā citādi. Mākslīgajā novecošanā straujāk izmainās gumiju raksturojošie parametri un īsākā laikā sasniedz savas kritiskās vērtības, pie kurām gumijas izstrādājums vairs nav lietojams. Dotajā darbā kā viens no šādiem parametriem ir izvēlēta dielektriskā caurlaidība, mākslīgā novecošana tiek veikta paaugstinātā temperatūrā.
  • Publication
    GRUNTS STIPRINĀŠANA AR ELEKTROOSMOTISKĀS METODES PALĪDZĪBU
    (1999)
    Aigars Metlāns
    ;
    Ainars Skabs
    ;
    Teirumnieks, Edmunds 
    ;
    Gunrads Vaļģis
    Daudzos gadījumos nepietiekoši nostiprinātas grunts dēļ notiek nogruvumi, kuri izraisa ēku, būvju daļēju vai pilnīgu sagraušanu. Šī problēma pastāvēja jau ļoti sen, bet asāk tā sāka izpausties tieši mūsu gadsimtā, sakarā ar ļoti straujo industrializāciju, kurai vajag gan daudz būvmateriālu, tādējādi izveidojas karjeri, gan arī nostiprināt tās platības, uz kurām tiks veikta ēku celtniecība.Lai gan pastāv ļoti daudzas grunts nostiprināšanas metodes, savā darbā mēs apskatījām tikai vienu - grunts masīva nostiprināšanas metodi ar elektroosmozes palīdzību, kurai tika veikti arī praktiskie eksperimenti. Metode balstās uz elektriskās strāvas izmantošanu grunts stiprināšanai, tas ir, uz to, ka ūdens virzās no pozitīvā elektroda uz negatīvo elektrodu, papildus veicot ūdens atsūknēšanu no šī elektroda.Elektroosmoze - tā ir šķīduma kustība attiecībā pret cietu sienu, elektropotenciālu starpības ietekmē jeb šeit šķidrums pārvietojas cietā vidē.
  • Publication
    ZĪDAIŅU MIRSTĪBA KĀ VIDES KVALITĀTES INDIKATORS LATGALĒ
    (1999)
    Matisovs, Ivars 
    Zīdaiņu mirstība atšķiras no kopējās iedzīvotāju mirstības problēmas ar savu īpašo sociālo, demogrāfisko un medicīnisko nozīmību. Tā ir viens no jūtīgākajiem jebkuras teritorijas vispārējā sociāli ekonomiskā, sanitārā un ekoloģiskā stāvokļa indikatoriem. Tādējādi zīdaiņu mirstību var uzskatīt par kompleksu vides kvalitātes indikatoru, ar vidi šajā gadījumā saprotot visu sociālo, ekonomisko un dabas faktoru un parādību kopumu, kas tiešā vai netiešā veidā ietekmē iedzīvotāju dzīves kvalitāti.
  • Publication
    Slēpto neironu loma tiešās izplatības tīklos
    (1999)
    Grabusts, Pēteris 
    Parādīta slēpto neironu loma tiešās izplatības mākslīgajos neironu tīklos. Slēpto neironu skaita izteiksme parasti tiek noteikta katrā atsevišķā gadījumā empīriski. Aprakstītas metodikas slēpto neironu skaita noteikšanai.
  • Publication
    EAST LATGALE SAA PROJECT
    (2001)
    Teirumnieks, Edmunds 
    ;
    Aigars Metlāns
    East - Latgale Region including Rezekne city and district and Ludza City and disrtict. East - Latgale region occupies 5241 km2 (about 8% o f Latvia). There are 120273 inhabitants (4,9% o f Latvia's population). Registration of waste volume in region is formal, because waste going to dumpsites as a matter of fact is not controlled exept dumpsites used by largest towns. In East - Latgale region in year 2000 was 46 dumpsites and total waste volume 64700 m3. National Municipal Solid Waste Management Strategy foreseeing establish 10-12 new solid waste landfills in Latvia. The overall strategy in searching for a location of a new landfill includes three principal aspects: 1. The environmental impact o f a landfill has to be as low as possible. 2. The waste disposal interests should not conflict with other interests. 3. The selected site should be reasonable from economic viewpoint. Taking into consideration the above aspects, the division of the land in areas suitable and non-suitable for location of a new landfill was based on the following criteria: Geological structure and hydrogeological conditions; Distance to urban areas; Location o f particularly protected nature objects; Distance to surface water bodies.
  • Publication
    APPLICATION OF CLUSTERING METHOD IN THE RBF NEURAL NETWORKS
    (2001)
    Grabusts, Pēteris 
    This paper describes one of classification algorithms, cluster analysis, that plays a significant role in the implementation of learning algorithm as applied to RBF-type artificial mural networks. The mathematical description of the K-means clustering algorithm is given and its implementation is demonstrated by experiment.
  • Publication
    Using grid-clustering methods in data classification
    (2002)
    Grabusts, Pēteris 
    ;
    A. Borisov
    This paper examines grid-clustering method. Unlike the conventional methods, this method organizes the space surrounding the patterns. It uses a multidimensional grid data structure. The resulting block partitioning of the value space is clustered via a neighbor search. The mathematical description of the algorithms employed is given. Some case studies and ideas on how to use the algorithms are described.
    Scopus© Citations 25
  • Publication
    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.
  • Publication
    EXTRACTING RULES FROM TRAINED RBF NEURAL NETWORKS
    (2005)
    Grabusts, Pēteris 
    This paper describes a method of rule extraction from trained artificial neural networks. The statement of the problem is given. The aim of rule extraction procedure and suitable neural networks for rule extraction are outlined. The RULEX rule extraction algorithm is discussed that is based on the radial basis function (RBF) neural network. The extracted rules can help discover and analyze the rule set hidden in data sets. The paper contains an implementation example, which is shown through standalone IRIS data set.
  • Publication
    GROUNDWATER, SURFACE WATER AND LEACHATE MONITORING IN HOUSEHOLD WASTE LANDFILL „GETLINI”
    (2005)
    Teirumnieks, Edmunds 
    ;
    Jānis Prols
    ;
    Aija Dēliņa
    The paper is about the largest landfill in Latvia Getlini. Waste from Riga city and surroundings are disposed here. The waste landfilling once was started in the old sand-gravel quarry, next to the Getlini bog, and no environment protection measures were taken. Currently total area of the Getlini landfill is 87 ha and 36 ha of it occupy the old dumpsite (waste hill). Contaminants from the waste with storm water leached to the over groundwater and under groundwater and contaminated it. In the paper contamination level and spreading of leachate, surface water and groundwater are described.
  • Publication
    FINANCIAL FORECASTING USING NEURAL NETWORKS
    (2006)
    Zorins, Aleksejs 
    This paper presents an application of neural networks to financial time-series forecasting. No additional indicators, but only the information contained in the sales time series was used to model and forecast stock exchange index. The forecasting is carried out by two different neural network learning algorithms – error backpropagation and Kohonen self-organising maps. The results are presented and their comparative analysis is performed in this article.
  • Publication
    DATA PREPROCESSING METHODS FOR INTERVAL BASED NEURAL NETWORK PREDICTION
    (2007)
    Zorins, Aleksejs 
    The paper examines a task of forecasting stock prices of Riga Stock exchange by the use of interval value prediction approach, which is carried out by modified Kohonen neural network learning algorithm. The data preprocessing methods are analyzed and implemented here to solve stock prices prediction task. The proposed data preprocessing methods has been experimentally tested with two types of artificial neural networks.
  • Publication
    INVESTIGATIONS OF MUNICIPAL SOLID WASLE LANDFILLS LEACHALE TREATMENT
    (2007)
    Teirumnieks, Edmunds 
    ;
    Līga Bērziņa-Cimdiņa
    ;
    Juris Mālers
    ;
    Gatis Pelčers
    ;
    Teirumnieka, Ērika 
    Municipal solid waste landfills are one of the most dangerous environment “point" polluters. The main polluter in landfills is leachate, which arise mainly of waste moisture and precipitations. Leachate is very contaminated wastewater and all landfills operators have problems in leachate treatment sector, because composition of leachate contaminants and concentrations very changed in time. It is very problematic task for selection of leachate treatment method or methods. Normally, in leachate treatment practice combination of different treatment methods are used. In this paper composition of leachate in two biggest Latvia landfills are described. Leachate treatment investigations were achieved with coagulation and sorbtion methods. In researches leachate with coagulants Al2(SOf3 and FeCl3 and peat as sorbent are treated. Researches showed that peat is very effective sorbent for heavy metals removing from leachate.
  • Publication
    TRANSFORMATION OF URBAN LANDSCAPEIN LATGALE REGION ON CHANGE OF 20- 21 CENTURIES
    (2007)
    Matisovs, Ivars 
    The paper deals with transformation of urban landscape in the 2 cities and 12 towns of Latgale region on change of 20-21 centuries, in the period from 1990 to 2007. Article provides information about factors and social economics processes that have influence on urban landscape structure and quality. The paper have a look at changes of land use structure, demographical processes, urban environmental quality, dynamics of urban transportation system and intensity of construction works in the cities and towns of Latgale region. The results establish disparities between scopes and directions of urban landscape transformation among different ranks of urban settlements.
  • Publication
    ECOLOGICAL EXPEDITION AS EFFECTIVE FORM OF ENVIRONMENTAL RESEARCH AND ECOLOGICAL EDUCATION
    (2007)
    Matisovs, Ivars 
    The paper deals with ecological expedition as effective form of environmental research and ecological education. Since 1997 Rēzekne Higher education institution organizes ecological expeditions for study programme “Environmental engineering” students in the Eastern Latvia region. Students realize integrated assessment of environmental quality with different methods. Article summarize experience of 10- years long period. Also show main goals and tasks of ecological expeditions, describe field research methods and cameral processing of data.
  • Publication
    Construction Methods of the Decision Trees for Genetic Programming
    (2008)
    Grabusts, Pēteris 
    Mūsdienās ģenētiskās programmēšanas iespējas tiek plaši izmantotas daudzos optimizācijas un klasifikācijas uzdevumos. Lai ģenētiskās programmēšanas metodes varētu tikt veiksmīgi pielietotas, ir nepieciešams konstruēt attiecīgus lēmumu kokus. Lēmumu koki un likumi uz to pamata ir intelektuālās datu analīzes sastāvdaļa un veiksmīgi tiek pielietoti klasifikācijas problēmu risināšanā. Pastāv vesela virkne dažādu paņēmienu, kas dod iespēju konstruēt lēmumu kokus ģenētiskās programmēšanas iespēju izmantošanai. Literatūras analīze liecina, ka optimālākā metode lēmumu koku konstruēšanā sastāv no diviem etapiem. Sākotnēji tiek veidots lēmumu koks, izmantojot C4.5 algoritmu, kas turpmāk tiek izvērsts ar ģenētiskās programmēšanas operatoru palīdzību. Šajā gadījumā ģenētiskā programmēšana tiek lietota kā globāla meklēšanas stratēģija precīza lēmumu koka atrašanā. Rakstā analizētas mūsdienu pieejas lēmumu koku konstruēšanā un izskatītas ģenētiskās programmēšanas iespējas, kas tiks izmantotas turpmākajā pētnieciskajā darbībā.
  • 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
    THE MATHEMATICAL MODELING OF METALS CONTENT IN PEAT
    (2009)
    Teirumnieks, Edmunds 
    ;
    Harijs Kalis
    ;
    Teirumnieka, Ērika 
    ;
    Kangro, Ilmārs 
    Metals deposition in peat can aid to evaluate impact of atmospheric or wastewaters pollution and thus can be a good indicator of recent and historical changes in the pollution loading. For peat using in agriculture, industrial, heat production etc. knowledge of peat metals content is important. Experimental determination of metals in peat is very long and expensive work. Using experimental data the mathematical model for calculation of concentrations of metals in different points for different layers is developed. The values of the metals (Ca, Mg, Fe, Sr, Cu, Zn, Mn, Pb, Cr, Ni, Se, Co, Cd, V, Mo) concentrations in different layers in peat taken from Knavu peat bog from four sites are determined using inductively coupled plasma optical emission spectrometer. Mathematical model for calculation of concentrations of metal has been described in the paper. As an example, mathematical models for calculation of Pb concentrations have been analyzed.
    Scopus© Citations 1
  • Publication
    REZEKNES AUGSTSKOLA INFORMATION SYSTEM SERVICE ORIENTED ARCHITECTURE SOLUTION
    (2009)
    Kijaško, Mihails
    The goal of this work is to analyze information about main principles of creating information systems using service oriented architecture and create RA integrated information system conceptual model. The proposed system model was developed based on service oriented architecture, with additional description of main principles. Final part contains RA information system service oriented architecture conceptual model with development principles. Using knowledge gathered from analyzes and examinations performed in this work, author gives proposals for integrated information system architecture development principles.
  • Publication
    DESCRIPTIVE MODEL OF SLIDING FRICTION PROCESSES
    (2009)
    Martinovs, Andris 
    ;
    Vladimir Gonca
    Paper analyses the sliding friction coefficient of rubber on concrete, timber and ceramic tile surfaces depending on the weight of the sliding object and contact surface area. It has been established that increase in the weight of the object makes sliding friction coefficient to grow. In the case of increase in size of contact area, sliding friction coefficient between rubber and concrete also increases, but it decreases between rubber- timber and rubber- tile. The mathematical model for description of sliding friction process has been developed which can be used to determine optimal surface area and a pattern as well as optimal weight of the sliding object in order to provide sufficient sliding friction. Model has five independent constants. It includes the contact surface area, the weight and the velocity of the sliding object, sliding friction coefficient, temperature and time.