18420 research outputs found
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Investigation of Electric Properties of Nanocomposites in Frequency Domain – Compact Measurement Data Representation
No full textStructure and Properties of Chemically Synthesized Ferrites and Magnetic Composites Based on Polycarbonate
No full textManufacturing and Characterization of Polyethylene Nanocomposites, Modified with Organically Treated Clays
No full textOccurence of Ragweed Plants and Pollen in Latvia
No full textRagweed poses a health and an agricultural risk that need to be assessed in Latvia by determining the growth of ragweed plants and pollen transported from local sources and neighboring countries. It has been stated that the northern border for the growth of ragweed exists at the 55o latitude north and Latvia is situated between the 55 and 58° latitude north. This study investigates the collection of ragweed plants during field studies of other plants (1970- 2007) and pollen collected from aerobiological monitoring in Riga starting from 2003. Ragweed is classified as an invasive plant species and was found growing alongside main transportation routes (railways and roads) in Latvia. The most harmful species, A. artemisiifolia, represented 84% of all the ragweed plants, followed by 9% of A. trifida and 5% of A. psilostachya. Field studies in 2007 that located ragweed were repeated, but no plants were found in the same locations in 2011. Herbariums have revealed that ragweed plants have flowered between the middle of July until September. Aerobiological studies have revealed ragweed pollen during the day within a two weeks period between late August and the start of September that suggests pollen from local sources. The pollen concentration only reached a concentration of 2-3 grains/m3 over the two weeks period starting in August. Ragweed pollen is presently not a threat in Latvia, but more studies need to be conducted to follow any changes over time
Inovatīvu pieeju izmantošana ēku energoefektivitātes politisko un tehnoloģisko risinājumu modelēšanā
No full textPieaugošais enerģijas patēriņš un izsīkstošie energoresursi liek domāt par enerģijas patēriņa samazināšanu un efektīvāku izmantošanu. Mājsaimniecību sektora enerģijas patēriņš ir 40 % no kopējā enerģijas patēriņa Eiropas Savienībā. Lai samazinātu šo enerģijas patēriņu Eiropas Savienībā ir pieņemta Eiropas Parlamenta un Padomes direktīva par enerģijas galapatēriņa efektivitāti un energoefektivitātes pakalpojumiem, kas paredz ES dalībvalstīm līdz 2016.gadam samazināt valstu enerģijas galapatēriņu par 9% attiecībā pret atskaites periodu.
Šī promocijas darba ietvaros apskatīts mājsaimniecību sektors, kas ir lielākais enerģijas patērētājs Latvijā un kurā paredzēts sasniegt lielāko enerģijas patēriņa ietaupījumu, lai izpidītu direktīvas prasības.
Promocijas darba ietvaros apskatīta ēku renovācijas norise un to ietekmējošie faktori un parametri. Apskatīts, kā dažādi energoefektivitātes paaugstināšanu veiconoši politikas instrumeti ietekmē ēku renovācijas procesa ātrumu un vai izmantojot šos politikas instrumentus iespējams sasniegt valsts noteikto mērķi. Promocijas darbā veikta modelēšana izmantojot sistēmdinamikas principus, apskatot kā dažādi procesi ir savstarpēji saistīti un kāda ir mijiedarbība starp tiem.
Tā kā bez ēku renovācijas tiek veikta arī jaunu ēku celtniecība, tad arī jaunajām ēkām jābūt energoefektīvām un ar pēc iespējas mazu enerģijas patēriņu. Eiropas Parlamenta un Padomes direktīva par ēku energoefektivitāti paredz, ka jau no 2020.gada visām jaunajām ēkām jābūt gandrīz nulles enerģijas ēkām. Esošie tehnoloģiskie risinājumi aukstā klimatā nevar nodrošināt gandrīz nulles enerģijas patēriņu.
Šī promocijas darba ietvaros izstrādāts tehnoloģiskais risinājums, kas aukstā klimatā palīdz sasniegt gandrīz nulles enerģijas ēku, samazinot apkures enerģijas patēriņu. Jaunais tehnoloģiskais risinājums izmanto ūdens – ledus fāzu pārejas latento enerģiju, lai samazinātu ēku siltuma vadīšanas zudumus, un tiek izmantots zema potenciāla siltums (grunts), lai atgūtu ūdens sasalšanas laikā zaudēto enerģiju. Izstrādātais tehnoloģiskais risinājums samazina ēku siltumvadīšanas zudumus aukstā klimatā – jo aukstāks klimats, jo lielāks ir siltuma vadīšanas zudumu ietaupījums. Šis tehnoloģiskais risinājums arī samazina ēkas apkures pīķa slodzi, kas dod iespēju ēkā uzstādīt mazākas jaudas apkures katlu un apsildes ierīces.
Promocijas darbam ir vairākas mērķa grupas, kas ietver politikas veidotājus un izstrādātājus, energoservisa uzņēmumus, jaunu tehnoloģiju ražotājus un ieviesējus, kā arī daudzdzīvokļu ēku un vienģimenes ēku iedzīvotājus
The Effect of Radiation Modification and of a Uniform Magnetic Field on the Deformation Properties of Polymer Composite Blends
No full textAn experimental study of radiation-modified blends of high-density polyethylene with a chlorinated polyethylene exposed to a constant magnetic field with induction equal to 0.7, 1.0, 1.4, and 1.8 T is presented. A preliminary gamma irradiation has been performed with absorbed doses equal to 50, 100, and 200 kGy. The main attention is devoted to the investigation of deformation (elastic and viscoelastic) properties of the material. Data showing the effect of the absorbed dose of gamma irradiation and the induction of magnetic field on the elastic modulus and creep of the material under a constant stress are obtained
Multimode Information Logistics for Conceptual Correspondence Monitoring
No full textThe paper addresses problems that arise in situations where conceptual correspondence
has to be monitored. This type of monitoring requires manual, semiautomatic
and automatic information processing and exposes high level of
complexity. The paper discusses challenges of use of multimode logistics in
monitoring conceptual correspondence and reports on how the challenges can
be met partly by using functional and morphological spaces of representation of
information logistics
The Modelling of Wood Material Flows in Order to Reduce Environmental Impact
No full textThe increase of total consumption of products and services is followed by increased extent of manufacturing and therefore larger impact on environment is generated by industries. In order to have higher profits and reduce the tax expenses, company is interested to reduce the amount of used raw materials, resources and emitted pollutants. Industrial symbiosis, which is a smart resource and material flow management, seeks to provide economical and environmental benefits by finding a suitable use for any waste or process by-product from one company within the manufacturing process of another company. Finding an application for manufacturing by-products reduces the need for landfilling and company can save funds that would have been spent. To define possible improvements that would lead to reduction of the impact on environment, the existing flows have to be acknowledged. The main objective of this paper is to define the actual flows of wood materials in wood processing industry in Latvia and to determine whether any inter-firm material exchanges and any occurrence of industrial symbiosis is present. The necessary data were compiled in an inventory that incorporates information about wood material flows in largest wood processing and furniture production companies in Latvia, including the amount, origin and destination of wood resources, produced materials and by-products. It is concluded that on-site reuse of wood manufacturing by-products – cuttings and sawdust – is typically performed in wood processing companies in Latvia. Altogether 10 inter-firm wood material exchanges, one energy exchange and two inter-firm synergies were found
Passive House Solutions for Climatic Conditions of Latvia
No full textStarting from the year 2021 all new buildings will need to
be zero energy therefore increased attention must be paid to
ways how to reduce the energy consumption of buildings. The
zero energy level can only be achieved by consuming very
small amount of energy for heating, ventilation, electricity and
hot water so this necessary energy can be produced by
renewable sources. Therefore these buildings will be similar to
today’s buildings of passive house standard. The paper
provides conclusions about what should be the necessary
thickness and heat transmission coefficients of insulation for
opaque elements - exterior walls, ground slabs and roofs as
well as the optimal sizes of the windows, their orientation and
heat-technical properties to achieve passive house standards in
Latvian climate. Also the paper presents economical
estimation and payback time calculation of zero energy
building constructions and engineer technical systems in
Latvia