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Modelling of surface crack growth under lubricated rolling-sliding contact loading
Boštjan Zafošnik, Zoran Ren, Jože Flašker, Gennady Mishuris, 2005, izvirni znanstveni članek

Opis: The paper describes modelling approach to computational simulation of surface crack growth subjected to lubricated rolling-sliding contact conditions. The model considers the size and orientation of the initial crack, normal and tangential loading due to rolling-sliding contact and the influence of fluid trapped inside the crack by a hydraulic pressure mechanism. The motion of the contact sliding load is simulated with different load cases. The strain energy density (SED) and maximum tangential stress (MTS) crack propagation criteria are modified to account for the influence of internal pressure along the crack surfaces due to trapped fluid. The developed model is used to simulate surface crack growth on a gear tooth flank, which has been also experimentally tested. It is shown that the crack growth path, determined with modified crack propagation criteria, is more accurately predicted than by using the criteria in its classical form.
Ključne besede: fracture mechanics, numerical methods, contact loading, finite element analysis, internal pressure, maximum tangential stress, strain energy density, surface crack growth
Objavljeno: 01.06.2012; Ogledov: 1200; Prenosov: 6
URL Polno besedilo (0,00 KB)

Lidija Čuček, 2013, doktorska disertacija

Opis: This doctoral dissertation, which consists of four substantive wholes, presents several syntheses of sustainable bioprocesses using computer-aided process engineering. In the first part the synthesis of different integrated processes of ethanol production from the entire corn plant is presented. The synthesis of different processes is in the second part further extended to the simplified and more comprehensive synthesis of bioproducts in the whole production supply chain network. Synthesis is based on the generic optimisation model of biomass production and supply chain networks. In the third part three methods for sustainable development assessment, suitable for multi-criteria optimisation, are presented: method of sustainability indexes, footprints and combined criteria, such as eco- and total profit. Methods are further upgraded with indirect effects in order to measure the unburdening the environment, associated with the use and replacement of environmentally-harmful products. Methods include the direct, indirect and total impacts on the environment. In the last part the methodology for reducing a large number of criteria within multi-objective optimisation to a small number of representative criteria is presented. This method is presented on the case of environmental footprints.
Ključne besede: Biomass energy generation, Supply chain networks, Synthesis of sustainable bioprocesses, Life Cycle Analysis, Sustainability assessment, Multi-objective optimisation, Dimensionality reduction, Representative Objectives Method
Objavljeno: 06.05.2013; Ogledov: 1161; Prenosov: 147
.pdf Polno besedilo (4,29 MB)

Coupled nonlineary problems in finite element analysis - a case study
Ivana Atanasovska, Meri Burzić, Tomaž Vuherer, Dejan Momčilović, 2012, objavljeni znanstveni prispevek na konferenci

Opis: The paper describes the Finite Element Method (FEM) analysis of elastic plastic deformation of steel tube impact absorbers for railway vehicles. Experiment investigation is used as a basis for FEM modelling and simulation. The developed FEM model includes material nonlinearity (plasticity), nonlinear contact and large deformation of finite elements. All aspects used in the absorber FEM model are explained in detail. The finite element analysis results for a chosen absorber are presented and discussed. The developed model opens the possibilities for future investigations of similar problems.
Ključne besede: kinetic energy absorber, railway, elastic plastic deformation, contact, finite element analysis
Objavljeno: 10.07.2015; Ogledov: 231; Prenosov: 2
URL Polno besedilo (0,00 KB)

Analysis of the Energy Market Operator activity in eight European countries
France Križanič, Žan Oplotnik, 2015, izvirni znanstveni članek

Opis: The article aims to analyze the connection between economic development, energy consumption, and prices of electricity and gas on one side and of the operation of the Energy Market Operator on the other. For this purpose we use a sample of eight EU countries with well-functioning energy markets but quite diverse characteristics. The results show that Market Operators in more developed countries in the sample have above average activity (according to revenue), and their primary goal is to achieve external economies. A higher level of Market Operator activity (greater revenue) is influenced by the decrease of transaction costs in energy markets and improves the prospect for greater use of energy. An active Market Operator is characteristically associated with international openness in the energy market as well as with the development of gas use in the given country. We find that a better equipped (greater assets used by the Market Operator) and more active (according to revenues) Market Operator is related with relatively higher levels of electricity and natural gas prices.
Ključne besede: energy, supply and demand, financial analysis, macroeconomics, international benchmark, comparison
Objavljeno: 06.07.2017; Ogledov: 29; Prenosov: 1
.pdf Polno besedilo (323,78 KB)

Geothermal heat potential - the source for heating greenhouses in Southestern Europe
Danijela Doberšek, Peter Trop, Darko Goričanec, 2016, izvirni znanstveni članek

Opis: The paper presents economically evaluated solutions for heating greenhouses with geothermal potential, if the same greenhouse is placed in two different locations in Southeastern Europe, one in Slovenia and the other in Serbia. The direct geothermal water exploitation using heat exchangers is presented and the remaining heat potential of already used geothermal water is exploited using high temperature heat pumps. Energy demands for heating greenhouses are calculated considering climatic parameters of both locations. Furthermore, different constructions materials are taken into account, and energy demands are evaluated if the same greenhouse is made of 4 mm toughened single glass, double insulated glass or polycarbonate plates. The results show that the geothermal energy usage is economically feasible in both locations, because payback periods are in range from two to almost eight years for different scenarios.
Ključne besede: geothermal heat exploitation, greenhouses energy demands, high temperature heat pump, economic analysis
Objavljeno: 07.07.2017; Ogledov: 52; Prenosov: 0
.pdf Polno besedilo (1,02 MB)

Underground coal gasification - the Velenje coal mine energy and economic calculations
Damjan Konovšek, Zdravko Praunseis, Jurij Avsec, Gorazd Berčič, Andrej Pohar, Simon Zavšek, Milan Medved, 2017, izvirni znanstveni članek

Opis: Underground coal gasification (UCG) is a viable possibility for the exploitation of vast coal deposits that are unreachable by conventional mining and can meet the energy, economic and environmental demands of the 21st century. Due to the complexity of the process, and the site-specific coal and seam properties, it is important to acknowledge all the available data and past experiences, in order to conduct a successful UCG operation. Slovenia has huge unmined reserves of coal, and therefore offers the possibility of an alternative use of this domestic primary energy source. According to the available underground coal gasification technology, the energy and economic assessment for the exploitation of coal to generate electricity and heat was made. A new procedure for the estimation of the energy efficiency of the coal gasification process, which is also used to compare the energy analyses for different examples of coal exploitation, was proposed, as well as the technological schemes and plant operating mode in Velenje, and the use of produced synthetic coal gas (syngas). The proposed location for the pilot demonstration experiment in Velenje Coal Mine was reviewed and the viability of the underground coal gasification project in Velenje was determined.
Ključne besede: underground coal gasification, syngas, clean coal technology, energy analysis, economic analysis
Objavljeno: 31.08.2017; Ogledov: 78; Prenosov: 6
.pdf Polno besedilo (1,32 MB)

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