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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Pagrindinių miško kirtimų projekto analizė Kuršėnų miškų urėdijos pavyzdžiu / The analysis of the project of the main deforestation as the example of Kursenai forestry

Matutis, Marijus 19 June 2006 (has links)
Matutis M. The analysis of the project of the main deforestation as the example of Kursenai forestry. Master’s work of forestry studies of forest economics/an adviser doc. A. Rutkauskas; LZUU, - Academy, 2006. – 96 p. 11 picture, 27 tables. Bibliography: 27 titles. SUMMARY In the master’s work there is reached the analysis of the project of the main deforestation as the example of Kursenai forestry. The object of the work: the wood of the forest groups of the state enterprise Kursenai forestry III (protective forests) and IV (economy forests). The objective of the work: to estimate the project of the main deforestation for the state enterprise Kursenai forestry during 1993 – 2005. The methods of the work: a) analysis; b) comparing; c) summation The methodic of the work: analysis of the documents, comparing of the indices and estimation of absolute and comparative volumes. The results of the work: the research was done and presented the main deforestation rates the most different were during 1994-1996, it increased even 25%, and the reason was the massive desiccation of the firs and the main rates of the deforestation were not adjusted. From 1997 the volume of truncated wood followed to the confirmed annual deforestation level, and from 1999 it exceeded in 0.3 thousand ktm. Or 0.5 %. And from 2002 there is strictly followed by the main deforestation rates. The keywords: the rate of the main deforestation; sub-economy, wood capacity, deflection.
2

Sistemos gedimo modeliavimas ir tikimybinis vertinimas / Modelling and Probabilistic Assessment of System Failure

Naujokaitis, Darius 25 August 2010 (has links)
Sistemų gedimo modeliavimas paprastai vykdomas taikant taip vadinamus gedimų medžius. Sistemos gedimo tikimybės ir gedimo atsiradimo priežasčių vertinimas dažniausiai atliekamas sudarant minimalių kirtimų aibę (MCS) ir pagal ją įvertinant gedimo tikimybę. Pastaruosius dvidešimt metų tiksliam gedimo tikimybės vertinimui yra taikoma dvejetainė sprendimų diagrama (BDD). Tačiau BDD sudarymo ir taikymo metodika vis dar yra tobulinama. Iki šiol Lietuvoje sistemos gedimo tikimybės vertinimui BDD dar nebuvo taikyta. Pristatant atliktą darbą aprašomi pagrindiniai MCS ir BDD sudarymo metodai bei jų taikymo ypatybės. Taip pat pateikiamas Kauno hidroelektrinės užtvankos vartų valdymo sistemos gedimo modelis ir gedimo tikimybės vertinimas. Šiuo tikslu buvo taikomi skirtingi MCS ir BDD sudarymo metodai bei atitinkamos programinės priemonės. Atlikus bandomuosius skaičiavimus taip pat pateikiamas gautų rezultatų palyginimas. Darbe apibūdinami pagrindiniai MCS ir BDD taikymo privalumai ir trūkumai bei pristatoma naujai sukurta programinė priemonė „DemoITE“. Taikant išanalizuotus algoritmus bei sukurtą programinę priemonę „DemoITE“ buvo ištirtos ir nustatytos sistemos gedimo priežastys bei tiksliai įvertinta sistemos gedimo tikimybė. Be to, pasiūlyta bazinių įvykių rangavimo principas, įgalinantis gauti mažiausią BDD struktūrą. / Modelling of system failure usually is performed applying so-called fault trees. Assessment of system failure probability and failure occurrence causes usually is performed developing a minimal cut-set (MCS) and according to it evaluating probability of system failure. The last twenty years a binary decision diagram (BDD) has been applied for the exact evaluation of system failure. However, a methodology of creation and application of BDD is still under development. Till now in Lithuania for the assessment of system failure probability BDD has not been applied yet. Presenting a performed work the main methods of development of MCS and BDD as well as features of their application is described. Also, the model and assessment of failure of Kaunas hydropower dam gates’ control system is presented. For this task the different methods of development of MCS and BDD as well as corresponding software was applied. Having performed the testing calculations a comparison of results is presented too. In the work the main advantages and disadvantages of MCS and BDD application are described and newly created software “DemoITE” is introduced. The developed algorithms and universal software “DemoITE” is used for visualization of failure causes and for exact estimation of the investigated system failure probability. Also, it is proposed the order of basic events on purpose to design the least BDD.
3

Ugdymo kirtimų projektavimas ir vertinimas / Planning and estimation of forest thinning

Banys, Tomas 09 June 2005 (has links)
The purpose of this study is to explore haw thinning planning standards agree with standards of estimation. Study was carried out in Kretinga forest enterprise Grūšlaukė forestry. Study of ratio of stands medial diameter and medial high was carried out in 11 – 60 years old pure spruce. The main purpose of thinning is to increase total productivity of forest stands and to form desirable structure and closeness of stands. It is important that all kinds of forest thinning concern biodiversity, increase resistance to wind and snow damage of forest stands, improve the quality of growing timber. Forests thinning use that timber part which rots in forests and gives no profit. To reach all these purpose forests thinning must be planned. Planning standard must be definite as it possible. It is important that these standards be suit with forests thinning normative. It was estimated that both standards has different rates and they are not matched. Thinning is planning by thickness of stands, but they are estimating by the number of trees in one hectare of stands. It was estimated that the ratio of forest stands medial diameter and medial high can be used in thinning planning. In pure spruce stands thinning must planned until ratio of medial diameter and medial high reach value: 0,8 in 11 – 20 years old stands; 0,9 in 21 – 40 years old stands; 1,0 in 41 – 60 years old stands.

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