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Reinforced piled embankment for a high-speed railway over soft soil
Yan Zhuang, Xiaoyan Cui, 2015, izvirni znanstveni članek

Opis: A geosynthetic, reinforced, piled embankment is an effective and economic method to solve the problems of possible bearing failure, unacceptable settlement and slope instability for an embankment built over soft soil; this has led to its widespread use, especially for high-speed railway embankments. Some design methods have been developed to assess the performance of these reinforced structures, which are mainly based on the results from small-scale models and numerical simulations. However, the reliability of these methods needs to be validated under full-scale field tests. This paper presents a numerical and analytical study for a full-scale field test of the Fengyang high-speed railway embankment. The results were analyzed and discussed in terms of the settlement of subsoil, the stressconcentration ratio (SCR), the axial force and the frictional stress of the pile. They showed that the settlement of the subsoil, from both the finite-element method (FEM) and the analytical method, were in good agreement with the measurement, and thus was a reliable parameter to assess the performance of the piled embankment with reasonable accuracy. The SCR was overestimated by the modified Terzaghi method, with a difference of 25%, while it was underestimated by the FEM, with a difference of approximately 20%. It was also shown that the tensile force in the reinforcement could be effectively assessed using the proposed analytical method, while it was overestimated by the FEM with a difference of 44%.
Ključne besede: reinforced piled embankment, high-speed railway, numerical simulation, analytical method
Objavljeno: 15.06.2018; Ogledov: 618; Prenosov: 43
.pdf Celotno besedilo (578,98 KB)
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Biomechanical characteristics of skeletal muscles and associations between running speed and contraction time in 8- to 13-year-old children
Jernej Završnik, Rado Pišot, Boštjan Šimunič, Peter Kokol, Helena Blažun, 2017, izvirni znanstveni članek

Opis: Objective: To investigate associations between running speeds and contraction times in 8- to 13-year-old children. Method: This longitudinal study analyzed tensiomyographic measurements of vastus lateralis and biceps femoris muscles’ contraction times and maximum running speeds in 107 children (53 boys, 54 girls). Data were evaluated using multiple correspondence analysis. Results: A gender difference existed between the vastus lateralis contraction times and running speeds. The running speed was less dependent on vastus lateralis contraction times in boys than in girls. Analysis of biceps femoris contraction times and running speeds revealed that running speeds of boys were much more structurally associated with contraction times than those of girls, for whom the association seemed chaotic. Conclusion: Joint category plots showed that contraction times of biceps femoris were associated much more closely with running speed than those of the vastus lateralis muscle. These results provide insight into a new dimension of children’s development.
Ključne besede: children, tensiomyography, running speed, contraction time, skelet muscle, motor development
Objavljeno: 13.07.2017; Ogledov: 675; Prenosov: 306
.pdf Celotno besedilo (454,48 KB)
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The influence of electric arc activation on the speed of heating and the structure of metal in welds
Oleksandr Savytsky, Mychailo Savytsky, Darko Bajić, Yuriy Shkrabalyuk, Tomaž Vuherer, 2016, izvirni znanstveni članek

Opis: This paper presents the results of a research related to the impact of electric arc activation onto drive welding energy and metal weld heating speed. It is confirmed that ATIG and AMIG methods, depending on metal thickness, single pass weldability and chemical composition of activating flux, enable the reduction of welding energy by 2-6 times when compared to conventional welding methods. Additionally, these procedures create conditions to increase metal weld heating speed up to 1,500-5,500 °C/s-1. Steel which can be rapidly heated, allows for a hardened structure to form (with carbon content up to 0.4%), together with a released martensitic structure or a mixture of bainitic-martensitic structures. Results of the research of effectiveness of ATIG and AMIG welding showed that increase in the penetration capability of electric arc, which increases welding productivity, is the visible side of ATIG and AMIG welding capabilities.
Ključne besede: arc welding, active flux, penetration, heating speed, driving energy
Objavljeno: 07.07.2017; Ogledov: 521; Prenosov: 273
.pdf Celotno besedilo (592,40 KB)
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Determining the speed of sound, density and bulk modulus of rapeseed oil, biodiesel and diesel fuel
Boban Nikolić, Breda Kegl, Saša Marković, Melanija Mitrović, 2012, izvirni znanstveni članek

Opis: Modern tendencies in the development of diesel engines include the operation of the system for injecting diesel fuel at pressures higher than 100 MPa. Knowing the characteristics of liquid fuels such as speed of sound, bulk modulus and density depending on pressure, is important for predicting the behavior of fuel injection systems for diesel engines and optimization of the same. The paper presents an original method and apparatus (device) for determining the speed of sound and density of fluids depending on the pressures. With this method, values of these characteristics for rapeseed oil, biodiesel and conventional diesel fuel at pressures up to 160 MPa are determined. The method is non-destructive, it can also be applied to higher pressures than 160 MPa, as well as other liquid fluids that are used at high pressure - hydraulic oil, for example.
Ključne besede: biodiesel, rapeseed oil, speed of sound, bulk modulus, density, high pressure
Objavljeno: 07.07.2017; Ogledov: 616; Prenosov: 284
.pdf Celotno besedilo (405,37 KB)
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Influence of the milling strategy on the durability of forging tools
Ivo Pahole, Dejan Studenčnik, Karl Gotlih, Mirko Ficko, Jože Balič, 2011, izvirni znanstveni članek

Opis: The quality of a tool's surface has a direct influence on the number of well-produced parts. For the machining of an active tool surface, two technological processes are used: electrical discharge machining and high-speed milling. These two processes are used when machining new tools and for the repairing of used forging tools. In both cases, the material has already been thermally treated, so it has to be used for hard milling. Practical experience shows that the milling strategy has a big influence on the durability of a forging tool. This paper shows the influence of the CNC machining direction during high-speed milling on the durability of the engraving within the forging tool. In some cases the correct milling strategy can increase the durability of the forging tool by about one third.
Ključne besede: orodja za kovanje, kakovost površine, visokohitrostno rezkanje, CNC-rezkanje, forging tools, surface quality, high speed cutting, CNC milling
Objavljeno: 10.07.2015; Ogledov: 835; Prenosov: 85
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Aerodynamic analysis of an oscillating airfoil in a power-extraction regime using the compressible Navier-Stokes equations with efficient and accurate low-speed preconditioning
Jernej Drofelnik, 2012, diplomsko delo

Opis: A wing that is simultaneously heaving and pitching may extract energy from an oncoming air flow, thus acting as turbine. The purpose of this study was to analyse the relationship between the aerodynamics and the theoretical performance of this device by means of timedependent laminar flow simulations performed with a research compressible finite volume Navier-Stokes solver COSA. In presented analyses, which confirm the findings of another independent study, the efficiency of the power extraction of this device can be of the order of 35 %, and such an efficient operating condition is characterized due to the favourable effects of a strong dynamic stall. This study is a part of a wider research programme of Dr. Campobasso’s group at University of Glasgow, aiming to develop a general-purpose computational framework for unsteady aerodynamic and aeroacoustic wind energy engineering. In view of aeroacoustic applications, the developed flow solver uses the compressible formulation of the Navier-Stokes equations with carefully optimized low-speed preconditioning. To demonstrate the modeling capabilities, the accuracy and the high computational performance of the developed low-speed preconditioning technology, the unsteady aerodynamics of the energy-extracting device is simulated by using a computationally challenging freestream Mach number of 0.001. A mixed preconditioning strategy that maintains both the nominal accuracy and the computational efficiency of the solver also for time-dependent low-speed problems is presented. A fundamental element of novelty of this study is a thorough assessment of the proposed approach partly based on the challenging and realistic problem associated with the oscillating wing device.
Ključne besede: Low-speed preconditioning, compressible multigrid Navier-Stokes solver, energy-extracting oscillating wing, computational fluid dynamics.
Objavljeno: 06.07.2012; Ogledov: 1962; Prenosov: 110
.pdf Celotno besedilo (2,40 MB)

The trans European railway network : three levels of services for the passengers
Milan Janić, 1996, izvirni znanstveni članek

Opis: The paper deals with the concept, analysis and measuring of the quality of services offered by the Trans European Railway Network (TERN). A sub-network serving the passengers travelling over the EU (European Union) and some of the non-EU regions are considered. Two sets of network attributes influencing the quality of services are analysed. One set of network physical attributes is represented by the length of the rail lines connecting specific origins and destinations of the passengers. The other set is represented by the time-based attributes used to measure the quality of services offered to the users. These are: travel speeds along particular lines (routes), and how the passenger's schedule delays depend on the train frequencies (e.g. number of trains offered on particular routes of the network in a given period of time). Considered as a common entity these attributes significantly influence the average passenger's travel time (and speed) which, together with out-of-pocket cost paid for travel, have appeared to be the most important criteria influencing the choice of transport mode.
Ključne besede: Trans European Railway Network, passenger transport, quality of services, travel speed, schedule day
Objavljeno: 05.06.2012; Ogledov: 1668; Prenosov: 23
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High-speed rail and air passenger transport : a comparison of the operational environmental performance
Milan Janić, 2003, izvirni znanstveni članek

Opis: This paper presents an overview of the environmental performance of high-speedrail (HSR) and air passenger transport (APT) in the European Union (EU). This performance embraces the direct environmental burdens/emissions such as energy consumption, air pollution, noise, landtake and land use, safety and congestion. A comparison of the marginal values of particular burdens/emissions and their costs (externalities) is carried out. The results have shown that significant mitigation of the impacts and savings of costs could be achieved by substitution of air passenger transport by high-speed rail. The substitution can be carried out through competition and complementarity of operations of both modes.
Ključne besede: high-speed rail, air passenger transport, interactions, environmental performance, burdens, emmisions, externalities
Objavljeno: 05.06.2012; Ogledov: 1507; Prenosov: 102
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