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1.
Back analysis of time-dependet displacement at the Trojane tunnel construction
Jakob Likar, 2004, original scientific article

Abstract: The 2,900-metre double tube tunnel of Trojane forms part of the highway section between Celje and Ljubljana and part of the highway road system connecting Lendava and Koper with adjacent roads. The construction of this section, which is of special importance for the Republic Slovenia, has been going on for almost ten years. The highway near Trojane where the tunnel is located, lies on a hilly terrain composed of Permian-carboniferous rocks, which are tectonically badly damaged in some places and marked with broad fault zones, containing tectonically remoulded soil of low strength in terms of deformability properties. Even though the amount of waters coming from the hills during the excavation of the tunnel was relatively small, this water, in combination with extremely damaged weak rock caused the increase of deformations at the construction site. Geological and geotechnical surveying with geometric monitoring and the analyses of stress and deformation changes in the surrounding rocks and support elements were critical in assessing the actual weak-rock conditions during the course of construction. Since the analyses of deformation processes, which had been modelled with PLAXIS 3D TUNNEL PROGRAM, showed great impact on permanent stability of the tunnel, special care was paid to rheological changes in the surrounding rocks and combined in-built support elements. 3D back analyses with SOFT-SOIL-CREEP (SSC) constitutive model, which takes into account rheological phenomena, were carried out. The calculations of primary and secondary stresses and deformations were made for two characteristic areas and determined on the basis of realistic geological mapping during tunnel construction. The first area represented typical rocks of the Trojane tunnel, i.e. shales and siltstone, while the second one was a tectonic zone where geological and geotechnical conditions during excavation were less favourable. The results of back analyses used provided an acceptable possibility for estimating the stress-strain variation during construction as well as an appropriate basis for analysing vertical displacements at the tunnel roof. The calculation results show good correlation with field measurements.
Keywords: tunnels, construction, permain-carboniferous rocks, geological-geotechnical conditions, tunnel support, Trojane tunnel, finite element method, costitutive models, back analyses, field mesurement, time dependent analysis
Published in DKUM: 15.05.2018; Views: 744; Downloads: 41
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2.
Financial system and agricultural growth in Ukraine
Olena Oliynyk, 2017, original scientific article

Abstract: Background/Purpose: An effective financial system should increase the efficiency of economic activities. This study provides evidence regarding the importance of financial development for agricultural growth in Ukraine. Methodology: We used non-integrated and integral indicators, time series and regression analysis to investigate the link between the financial development and agricultural growth. Results: The results based on integral indicators shows that the financial development does not affect agricultural growth in Ukraine. The study based on non-integrated indicators, which characterizes various aspects of the financial system’s banking component and agricultural growth, provided a significant link between the financial system and agriculture growth. The regression models revealed if bank deposits to GDP (%) increases the value added per worker in agriculture increases exponentially. The results of the study indicate that, agriculture is more sensitive to lending changes than the vast majority of other sectors of the economy. The increasing lending of one UAH (Ukrainian hryvnia) resulted in retail turnover growth of 1.62 UAH, while agricultural gross output, growth was UAH 5.06. Conclusion: Our results reveal a positive relationship between financial system’s banking component and agriculture growth in Ukraine. The results indicate the necessity for continued research into further developing universal methodological approaches of appraising the nexus of the financial system’s banking component on agriculture growth in general as well separate farm groups. The results of our study has important implications on policy making authorities efforts to stimulate agricultural growth by improving the efficiency of the financial system’s banking component.
Keywords: agricultural growth, the integral indicator of the agricultural growth, the integral indicator of the financial development, time series analysis, regression analysis, financial system
Published in DKUM: 04.05.2018; Views: 851; Downloads: 300
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3.
Container throughput forecasting using dynamic factor analysis and ARIMAX model
Marko Intihar, Tomaž Kramberger, Dejan Dragan, 2017, original scientific article

Abstract: The paper examines the impact of integration of macroeconomic indicators on the accuracy of container throughput time series forecasting model. For this purpose, a Dynamic factor analysis and AutoRegressive Integrated Moving-Average model with eXogenous inputs (ARIMAX) are used. Both methodologies are integrated into a novel four-stage heuristic procedure. Firstly, dynamic factors are extracted from external macroeconomic indicators influencing the observed throughput. Secondly, the family of ARIMAX models of different orders is generated based on the derived factors. In the third stage, the diagnostic and goodness-of-fit testing is applied, which includes statistical criteria such as fit performance, information criteria, and parsimony. Finally, the best model is heuristically selected and tested on the real data of the Port of Koper. The results show that by applying macroeconomic indicators into the forecasting model, more accurate future throughput forecasts can be achieved. The model is also used to produce future forecasts for the next four years indicating a more oscillatory behaviour in (2018-2020). Hence, care must be taken concerning any bigger investment decisions initiated from the management side. It is believed that the proposed model might be a useful reinforcement of the existing forecasting module in the observed port.
Keywords: container throughput forecasting, ARIMAX model, dynamic factor analysis, exogenous macroeconomic indicators, time series analysis
Published in DKUM: 12.12.2017; Views: 1175; Downloads: 329
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4.
Simulations of VoIP applications in INET framework
Sebastijan Horvatić, 2017, master's thesis

Abstract: This master's thesis describes the support for modelling Voice over Internet Protocol (VoIP) applications in the INET Framework. First, it briefly presents the VoIP technology and factors responsible for the VoIP quality of service. Next, the thesis moves on to discuss the OMNeT++ environment and the INET Framework, their installation and usage. Following this, it examines all of the INET packages and modules available for VoIP modelling, with all VoIP-related INET examples then shortly described and tested. By using INET, our own network and application models are created and simulated using different parameters. Comparisons of the simulation results are carried out and some of the best-found parameters for the VoIP communications are presented. At last, the calculation of jitter by using the obtained simulation results and Excel program is described, because jitter is not shown in the simulation results in INET.
Keywords: voice over internet protocol, performance analysis, simulation, real-time transport protocol, user datagram protocol
Published in DKUM: 18.08.2017; Views: 885; Downloads: 96
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5.
The importance of using discounted cash flow methodology in techno-economic analyses of energy and chemical production plants
Zorka Novak-Pintarič, Zdravko Kravanja, 2017, original scientific article

Abstract: This paper demonstrates the correct application of discounted cash flow methodology for evaluating and designing energy and chemical production plants. Such processes usually correspond to capital intensive long-term projects. Simple economic criteria, like the profit or production cost are insufficient for this type of decision making because they do not take into account the time value of money and underestimate the profitabilities of the evaluated plants. This paper shows that some of those criteria based on the discounted cash flows establish suitable compromises between long-term cash flow generation and profitability. As several alternative options are usually evaluated in parallel, it is shown how to rank mutually exclusive alternatives properly and how to select the best option from among them. Two large-scale case studies demonstrate that using discounted cash flow methodology can result in substantially different decisions than non-discounted criteria, however, these decisions are affected by several input parameters.
Keywords: discounted cash flow analysis, time value of money, net preset value, profitability, process
Published in DKUM: 04.08.2017; Views: 657; Downloads: 370
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6.
Methods for detecting fatigue cracks in gears
Aleš Belšak, Jože Flašker, 2009, published scientific conference contribution

Abstract: A crack in the tooth root is the least desirable damage caused to gear units and it often causes failure of gear unit operation. For fault analyses presented in this article, gear units with real damages or faults produced on the basis of numerical simulations of real operating conditions are used; tests were carried out in a laboratory test plant. Damages in gear units can be identified by monitoring vibrations. The influences of a crack in a single-stage gear unit on produced vibrations are presented. Significant changes in tooth stiffness are caused by a fatigue crack in the tooth root whereas, in relation to other faults, changes of other dynamic parameters are more expressed. Non-stationary signals are analysed, using the family of Time Frequency Analysis tools, which include Wavelets and Joint Time Frequency Analyses.
Keywords: gear unit, vibrations, tooth root, time frequency analysis tool
Published in DKUM: 30.06.2017; Views: 700; Downloads: 342
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7.
A new method for determining extra time by considering ergonomic loads in the garment and metal working industries
Vekoslav Verhovnik, Andrej Polajnar, 1993, original scientific article

Abstract: The changing labour conditions in the garment and metal-working industries have led to the necessity of determining new extra times to establish the time standard. In this paper, a method of measuring stress and strain imposed upon the operator in new working conditions by determining the additional production coefficient is presented. The method gives criteria and grades to assess stress at the workplace. Physical stress (dynamic and static), thermal and visual stress, discomfort caused by noise, aerosols, gases and vapours, and the stress due to monotony are assessed. The stresses are expressed by ecological, physiological and psychological indexes. The indexes are pondered. Ponderation includes the factor of the magnitude and the time of exposure to stress. Ponderation is expressed by the number of points, the total being an adequate presentation of the stresses. Stress and strain decrease the working performance of the operator. Therefore they must be included in the standard to compensate for the operator's lower working efficiency due to physical and psychological strain at the workplace, Short breaks and stops allowed during work enable the operator to perform work tasks without getting excessively tired. The necessary correction of the production time is made by applying the ergonomic coefficient Ker.
Keywords: job analysis, production planning, stress assessment, time study, working conditions, working environment
Published in DKUM: 30.03.2017; Views: 751; Downloads: 100
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