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Wyszukujesz frazę "Dimitrov, D." wg kryterium: Autor

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    Wyświetlanie 1-5 z 5
    Tytuł:
    Biomass of the xerothermic oak ecosystem on a site of community importance, BG0001040 "Zapadna Stara Planina i Predbalkan", Bulgaria
    Autorzy:
    Lyubenova, M.
    Dimitrova, V.
    Georgieva, N.
    Dimitrov, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/52482.pdf
    Data publikacji:
    2014
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Technologii Drewna
    Tematy:
    biomass
    xerothermic plant
    forest ecosystem
    oak
    plant community
    Quercus frainetto-Quercus cerris forest
    Zapadna Stara Planina i Predbalkan area
    Natura 2000 area
    Bulgaria
    Opis:
    The belowground and aboveground biomass was estimated for the tree story, sproutsand seedling regeneration in a representative Quercus frainetto – Quercus cerris ecosystem on “Zapadna Stara planina i Predbalkan”, a Site of Community Importance (SCI). The biomass was measured by destructive sampling (on sample or “model trees” representing three calculated density classes for each species and cut at the stump) of leaves, annual and perennial branches, wood, bark and root components. The belowground (root) biomass was also calculated from a subsample. The data obtained were compared to the results of previous studies and the values on the Bazilevich and Rodin [1971] scale. The ecological status of the forest ecosystem studied and its functional efficiency are discussed based on the study results and specific climate data.
    Źródło:
    Drewno. Prace Naukowe. Doniesienia. Komunikaty; 2014, 57, 192
    1644-3985
    Pojawia się w:
    Drewno. Prace Naukowe. Doniesienia. Komunikaty
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Greens functions and existence of solutions of nonlinear fractional implicit difference equations with Dirichlet boundary conditions
    Autorzy:
    Cabada, Alberto
    Dimitrov, Nikolay D.
    Jonnalagadda, Jagan Mohan
    Powiązania:
    https://bibliotekanauki.pl/articles/29519501.pdf
    Data publikacji:
    2024
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
    Tematy:
    fractional difference
    Dirichlet conditions
    Green’s function
    existence of solutions
    Opis:
    This article is devoted to deduce the expression of the Green’s function related to a general constant coefficients fractional difference equation coupled to Dirichlet conditions. In this case, due to the points where some of the fractional operators are applied, we are in presence of an implicit fractional difference equation. So, due to such a property, it is more complicated to calculate and manage the expression of the Green’s function than in the explicit case studied in a previous work of the authors. Contrary to the explicit case, where it is shown that the Green’s function is constructed as finite sums, the Green’s function constructed here is an infinite series. This fact makes necessary to impose more restrictive assumptions on the parameters that appear in the equation. The expression of the Green’s function will be deduced from the Laplace transform on the time scales of the integers. We point out that, despite the implicit character of the considered equation, we can have an explicit expression of the solution by means of the expression of the Green’s function. These two facts are not incompatible. Even more, this method allows us to have an explicit expression of the solution of an implicit problem. Finally, we prove two existence results for nonlinear problems, via suitable fixed point theorems.
    Źródło:
    Opuscula Mathematica; 2024, 44, 2; 167-195
    1232-9274
    2300-6919
    Pojawia się w:
    Opuscula Mathematica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Adaptive potential and productivity of two Salix viminalis L. clonal varieties grown in North Central Bulgaria
    Autorzy:
    Stankova, T.
    Gyuleva, V.
    Tsvetkov, I.
    Popov, E.
    Kalmukov, K.
    Dimitrov, D.N.
    Andonova, E.
    Stefanova, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/2130197.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Instytut Dendrologii PAN
    Tematy:
    basket willow
    spacing
    rotation
    allometry
    site conditions
    Opis:
    Salix viminalis L. is a broadly cultivated willow species that has been intensively used for breeding purposes, particularly in selection of clones and hybrids for biomass production. The present study aimed to explore and compare growth and adaptability of two basket willow (Salix viminalis L.) clonal varieties - rubra and purpurea - at the specific edaphic and climate conditions and cultivation practice presented in an experimental plantation in North Central Bulgaria. The influence of spacing, genotype, root age and rotation on their productivity were also investigated and allometric relationships for non-destructive estimation of woody plant biomass were suggested. The trial plantation was established in the spring of 2018 as 4 sectors of a Nelder wheel plot with 15 nearly-square spacings, ranging from 0.25 to 9.80 m2 (40000–1020 plants per hectare). The two varieties were arranged in 4 four-spoke sectors (2 sectors per clone). Data collection took place from 2018 to 2020 and comprised 1- and 2-year rotations. The study showed that Salix viminalis var. rubra was more susceptible to desiccation-causing adverse climatic changes, poorly adapted to the specific conditions of the study site and gradually died out during the second and the third year. Salix viminalis var. purpurea exhibited steady survival rate (97 - 77%) and annual biomass productivity varying from 3 to 17 Mg/ha/year across the densities, sectors and years. During the first year of growth purpurea variety had a significantly higher plant weight and sprout number than rubra variety. Growing space affected positively the number of shoots and tree dendromass, and sprouting was reinforced by coppicing that doubled the shoot number during the subsequent rotation. This was reflected in the development of the stump-level allometric models that were differentiated according to rotation. The stump-level allometric model of higher predictive power was based on the main shoot length and shoot number. An exponential relationship to the breast-height shoot diameter was also suggested for biomass estimation of each sprout separately.
    Źródło:
    Dendrobiology; 2022, 88; 1-15
    1641-1307
    Pojawia się w:
    Dendrobiology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effective aggregating of tractors for transportation
    Racjonalne agregatowanie ciągników do transportu
    Autorzy:
    Dimitrov, P.
    Simenov, D.
    Stoyanov, K.
    Kangalov, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/375070.pdf
    Data publikacji:
    2012
    Wydawca:
    Politechnika Śląska. Wydawnictwo Politechniki Śląskiej
    Tematy:
    traktor
    model matematyczny
    transport
    tractor
    mathematical model
    Opis:
    The paper discusses the importance of tractors for the technological and transportation activities in agriculture. It also presents a methodological approach and an algorithm based on the criteria for the full utilization of the tractors' gravity and power for the successful aggregating of tractors when performing these activities. The offered mathematical model makes it possible to determine the sphere of full aggregation of tractors in transport within the broad range of change of the production conditions' indicators with the help of board computers.
    Źródło:
    Transport Problems; 2012, 7, 3; 25-28
    1896-0596
    2300-861X
    Pojawia się w:
    Transport Problems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Element enrichment and provenance of the detrital component in Holocene sediments from the Western Black Sea
    Autorzy:
    Dekov, V.M.
    Darakchieva, V.Y.
    Billstrom, K.
    Garbe-Schonberg, C.D.
    Kamenov, G.D.
    Gallinari, M.
    Dimitrov, L.
    Ragueneau, O.
    Kooijman, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/2079273.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    trace element concentration
    isotope analysis
    enrichment factor
    Holocene sediment
    catchment area
    geochemical analysis
    Black Sea
    Opis:
    Concentrations of a large set of major and trace elements, and Sr, Nd and Pb isotope ratios were measured in Holocene sediments cored in the western deep Black Sea in order to unravel: (1) the controls of element enrichment, and (2) sources of the detrital component. The transition of the basin from oxic to euxinic resulted in enrichment or depletion in a number of elements in the deep-sea sediments. Authigenic Fe enrichment appears to depend on the amount of Fe mobilized from the sediment through the benthic redox shuttle mechanism and free H2S in the water column (degree of “euxinization”). Manganese enrichment is controlled by diagenetic reactions within the sediment: the dissolution of Mn minerals, Mn2+ diffusion upward and reprecipitation. Barium enrichment is also controlled by diagenetic reactions, sulfate reduction and methanogenesis, that take place above and below the sulfate-methane transition, respectively. The major part of V, Co, Ni, Cu, Zn, Cr, Mo, Cd and Sb is inferred to have co-precipitated with Fe in the euxinic deep waters and to have been incorporated into authigenic Fe-sulfides. Basin reservoir effect additionally influences the Mo enrichment. The U enrichment is interpreted to have a different origin in the two organic-rich stratigraphic units (II and I). It is inferred to be: (i) at the expense of the U inventory of the deepwater pool and a result of inorganic reduction of U at euxinic conditions in the lower Unit II; and (ii) at the expense of the U inventory of the surface water pool and a result of biogenic uptake and transfer to the sediment by the plankton in the upper Unit I. The high field strength elements are closely linked to the detrital component and their depletion in the organic-rich sediments reflects a dilution of the detrital component by the biogenic one. The enrichments of REE, Sn and Th are likely controlled by adsorption on clay minerals. Sr-Nd-Pb isotope compositions of the alumino-silicate component of the studied sediments are relatively uniform. They are most likely controlled by riverine suspended matter supplied mainly in the NW Black Sea (Danube Delta) and transported southward by marine currents, and to a lesser degree by suspended matter from the small rivers draining SE Bulgaria and NW Turkey. Wind-blown dust from the Sahara Desert appears to have a minor contribution to the alumino-silicate component of the sediments. The slight shift in the Pb isotopes in Unit I upper layers is possibly caused by the addition of anthropogenic Pb.
    Źródło:
    Oceanologia; 2020, 62, 2; 139-163
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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