Journal of Mechanical Engineering 56 (2010)1

SV-JME-1-2010 in digital form »

 

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Countrywide Positioning of Domestic Solar Water Heating Systems using Risk Analysis and Geographical Information System

Corresponding author - Luka Lugarić

Authors - Ljubomir Majdandžić - Davor Škrlec

Abstract

In this paper, choosing appropriate locations for household solar water heating systems within a country is based on assessing project feasibility by using solar irradiation integrated in a geographical information system (GIS) and investment risk analysis, based on uncertainties in project input variables. Current indicators and statistics of solar systems of EU and Croatia are given, followed by impacting factors on investments in domestic SWH. Investment risks are determined. GIS is constructed to assess solar irradiation potential on a countrywide scale.
A spreadsheet model for financial analysis using the Monte Carlo method for probabilistic simulation of uncertain project parameters is shown, which integrates GIS and determines a financial feasibility for two case studies. Financial indicators of net present value (NPV), internal rate of return (IRR) and simple payback time (SPB) are shown for three investment strategies, varying in financial resources according to profiled income categories of households in the country. A sensitivity analysis has been performed to determine the impact of individual risks on the financial outcome of the project. Financial flows are compared to determine the difference in feasibility for the same project on two different locations. Probability distributions for risks and financial indicators are shown.

Keywords - solar systems, alternative energy sources, heating water, geographical information system, investment risk, analysis

Paper's information

Strojniški vestnik - Journal of Mechanical Engineering 56(2010)1, 3-17 
UDC 620.92

 Countrywide Positioning of Domestic Solar Water Heating Systems using Risk Analysis and Geographical Information System (pdf)

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Effectivity of Hypergeometric Function Application in the Numerical Simulation of the Helicopter Rotor Blades Theory

Corresponding author - Dragoljub Bekrić

Avtorji - Časlav Mitrović - Dragan Cvetković - Aleksandar Bengin

Abstract

Efficiency and justification of hypergeometric functions application in achieving simple formulas used in numerical simulation of helicopter rotor blades theory are presented in this paper.
Basic equations of stream field over helicopter rotor are formulated, their decomposition is made and mean induced velocity harmonics are integrally presented. Theoretical basis of hypergeometric function application in transformation of integral equations of k-bladed rotor average induced velocity into special functions follows. The necessary conditions for transformation hypergeometric functions into special functions are defined.
Variants of integral transformation of expressions obtained are presented by a numerical simulation and solutions are found. This approach to cecure the effectivity of hypergeometric function application in helicopter rotor blades theory by numerical simulation provides a synthetic method, which can be used to define helicopter k-bladed main rotor optimal characteristics.

Keywords - hypergeometric functions, unsteady flow, numerical simulation, lifting line, free vortex model, helicopter rotor aerodynamics

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 56(2010)1, 18-22 
UDC 629.735.45-25

 Effectivity of Hypergeometric Function Application in the Numerical Simulation of the Helicopter Rotor Blades Theory (pdf)

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The Influence of Surface Topology on the Accuracy of Laser Triangulation Scanning Results

Corresponding author - Nikola Vukašinović

Authors - Marjan Korošec - Jože Duhovnik

Abstract

This paper discusses the influence of surface topology on the accuracy of laser triangulation scanning results. Scanning distance and scanning angle of impact laser beam was found to be the most crucial interaction between the surface topology and scanning process. Therefore, we focused these two parameters while other parameters like microstructure, colour of surface, optical settings remained fixed. Despite of random nature of freeform surfaces, the measurements were systematic, according to the principles of the design of experiment (DOE) adjusting angle and distance in the whole scanning range. Based on the results of this research and prior estimation of surface complexity, an implication or working area range prediction, as well as the determination of optimal set of influence parameters inside this particular working area can be done.

Keywords - laser measurer, surface topology, design of experiment (DOE), reverse engineering, laser scanning, laser triangulation

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 56(2010)1, 23-30 
UDC 621.37

 The Influence of Surface Topology on the Accuracy of Laser Triangulation Scanning Results (pdf)

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Muscular-Skeletal Diseases Require Scientifically Designed Sewing Workstations

Corresponding author - Andrej Polajnar

Authors - Marjan Leber - Natasa Vujica Herzog

Abstract

The paper describes the adjustment of the sewing workstation with respect to working postures and workers’ perceptions based on the results of a survey research carried out in 32 sewing workstations in different garment production factories in Slovenia. Poor posture of the trunk, neck and upper extremities, and the monotonous repetitive movements result in a high prevalence of musculoskeletal complaints affecting back, neck and upper extremities among sewing machine operators.
Several studies have confirmed that working postures are still a common problem in garment industry and ergonomically designed workstations can considerably reduce the above-mentioned problems. Therefore, the main purpose of the paper is to formulate all ergonomic recommendations for the modification of sewing machine workstations .

Keywords - dressmakers, working station, working postures, musculoskeletal diseases, prevention

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 56(2010)1, 31-40 
UDC 746.4

 Muscular-Skeletal Diseases Require Scientifically Designed Sewing Workstation (pdf)

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Risk Analysis Methodology for Road Tunnels and Alternative Routes

Corresponding author - Stojan Petelin

Authors - Blaž Luin - Peter Vidmar

Abstract

The work includes an overview of road tunnel risk analysis methodologies that have been developed in Europe as a consequence of several major accidents and subsequent Directive on minimum safety requirements for road tunnels. In our analysis, we used PIARC - OECD quantitative risk assessment model (QRAM), which includes the largest choice of different scenarios, tunnel types and traffic parameters. On the other hand, it does not include several risk reduction measures, which we managed to assess in our methodology by combining the QRAM with scenario based analysis in which we used 1D ventilation model, CFD fire model simulation and evacuation model. Apart from this, we present a calculation of risk acceptability criteria for Slovenia. There is also a description of risk assessment procedure and an example case study in which risk assessment of bidirectional and unidirectional traffic through a tunnel is carried out.

Keywords - risk analysis, quantitative risk analysis, road tunnel, tunnel fire, tunnel ventilation, traffic, risk acceptability criteria

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 56(2010)1, 41-51 
UDC 624.19

 Risk Analysis Methodology for Road Tunnels and Alternative Routes (pdf)

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Modelling Metal cutting Parameters Using Intelligent Techniques

Corresponding author - Dejan Tanikić

Authors - Miodrag Manić - Goran Devedžić - Zoran Stević

Abstract

Cutting temperature, which depends on many factors, has a significant and, mostly negative influence on cutting process parameters. On the other hand, the quality of the machined surface is one of the most important qualitative indicators of a cutting process. Both parameters cannot be omitted in the modeling of metal cutting. Due to the high complexity of the process itself, it is almost impossible to encompass all the relevant factors and their influence within a mathematical formula. In such cases, it is much more efficient to use and process data obtained through experiments. Nowadays, systems that are based on artificial intelligence are often used for this purpose. The paper presents the application of the artificial neural networks and hybrid, neuro-fuzzy model in the prediction of a workpiece temperature and surface roughness. The approach is based on the thermographic method and infra red camera imaging system.

Keywords - cutting process, artificial neural networks, neuro-fuzzy model

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 56(2010)1, 52-62 
UDC 679.8.053:622.34

 Modelling Metal cutting Parameters Using Intelligent Techniques  (pdf)

 

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A Multi-Criteria Assessment of Energy Crops for Biogas Production

Corresponding author - Peter Vindiš

Authors - Bogomir Muršec- Črtomir Rozman- Franc Čus

Abstract
This paper presents the system for the assessment of energy crops for biogas production. The system is based on simulation modelling and multi criteria decision analysis. The deterministic simulation system consists of deterministic production simulation models that enable different types of costs calculations for the production of energy crops, electrical and heat energy in biogas production. Simulation model results were further evaluated using a qualitative multi-attribute modelling methodology (supported by the software tool DEX-i) and quantitative analytical hierarchical process – AHP (supported by the software tool Expert Choice 2000TM). The analysis showed that by using current model the most relevant alternative used for energy crop for biogas production is maize. The maize results in the best multicriteria evaluation EC = 0.248 and DEX-i evaluation = appropriate. The best alternative for maize is sorghum with multicriteria evaluation of EC = 0.201 and DEX-i evaluation = less appropriate.

Keywords - simulation model, Expert Choice (AHP), DEX – i, energy crops, biogas

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 56(2010)1, 63-70 
UDC 662.767.2

 A Multi-Criteria Assessment of Energy Crops for Biogas Production (pdf)

 

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