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Vizualizacija procesa preoblikovanja s krmilnikom in mikro zaslonom
Bojan Vidovič, 2018, diplomsko delo

Opis: Diplomsko delo opisuje avtomatizacijo in vizualizacijo elektropnevmatskega sistema z mikro krmilnikom ter mikro zaslonom na dotik. Predstavljeni so tako postopki programiranja in vizualizacije procesa kakor tudi uporabljena strojna oprema Siemens S7-200 ter Micro Panel – SIMATIC TP 177micro. Pričujoče delo opisuje tudi povezave z resničnim sistemom, različne možnosti uporabe programske opreme SIMATIC WinCC Flexible Advanced in težave, s katerimi se lahko pri uporabi srečujemo, poleg tega pa še programski paket STEP 7-Micro/WIN, uporabljen za programiranje krmilnika. Po korakih so predstavljene tudi informacije ter postopki, potrebni za konfiguracijo programov in strojne opreme ter povezavo med njimi.
Ključne besede: PLK, HMI, elektropnevmatski sistem, STEP 7-Micro/WIN, Siemens SIMATIC S7-200, Siemens SIMATIC WinCC flexible Advanced, Micro Panel – SIMATIC TP 177micro.
Objavljeno: 26.09.2018; Ogledov: 478; Prenosov: 73
.pdf Celotno besedilo (2,34 MB)
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Micro-scale responses of granular materials under different confining pressures using the discrete element method
Mahmud Sazzad, 2016, izvirni znanstveni članek

Opis: Biaxial compression tests were carried out on assemblies of ovals to study the micro-scale responses of granular materials under different confining pressures using the discrete element method (DEM). A total of 8450 ovals were generated in a rectangular frame without any overlap. Four dense samples were prepared from the initially generated sparse sample under different confining pressures. The simulated results yield a stress-straindilatancy behaviour similar to that observed in sands under different confining pressures. The evolution of the different microparameters and their inter-relationships are established. When the confining pressure is relatively high, the difference between the coordination number and the effective coordination number is very small; however, the difference is apparent for a low confining pressure. The microtopology of the granular assembly at several important states of shear is also reported. It is noted that the topological distribution of the granular materials is confining- pressure dependent. The normalized void-cell number is a minimum under the lowest confining pressure, whereas the same number is a maximum under the highest confining pressure. A linear relationship is observed between the normalized void-cell number and the effective coordination number, regardless of the confining pressures. The evolution of the deviatoric fabric for different confining pressures is measured and the macro-micro relationship is presented.
Ključne besede: microstructures, confining pressure, fabric, microtopology, coordination number, macro-micro relationship
Objavljeno: 15.06.2018; Ogledov: 551; Prenosov: 42
.pdf Celotno besedilo (440,72 KB)
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A comparison between conventional triaxial and plane-strain compression on a particulate system using 3D DEM
Mahmud Sazzad, Kiichi Suzuki, 2012, izvirni znanstveni članek

Opis: Granular materials such as sand are subjected to different stress paths depending on the in-situ conditions. For example, a granular system under the foundations experiences conventional triaxial compression (CTC), while it experiences plane-strain compression (PSC) in the case of the embankment of roads. Due to the difference in the stress paths, the behavior of granular materials also becomes different. This paper aims at comparing the behavior of granular materials under CTC and PSC conditions using the 3D discrete-element method (DEM). An isotropically compressed dense sample consisting of 8000 spheres was prepared numerically using periodic boundaries. The CTC and PSC tests were simulated using the same isotropically compressed dense sample to compare and explore the macro- and micro-mechanical responses of granular materials without any bias from the initial fabric of the numerical sample. Qualitatively, the simulated stress-strain responses are consistent with that observed in the experimental studies. The dilatancy index is found to be independent of the stress paths used in the present study. The b value (defined as b = (σ2 − σ3)/(σ1 − σ3) where σ1, σ2 and σ3 are the stresses in the x1 -, x2 - and x3 - directions, respectively) - axial strain curve has a close similarity with the stress ratio - axial strain curve for the PSC test. The evolution of the coordination number and the sliding contact fraction is independent of the stress paths. A link between the macro- and micro-quantities is observed and a unique macro-micro relationship is noticed, regardless of the stress paths applied in this study.
Ključne besede: conventional triaxial compression, plane-strain compression, micro response, DEM
Objavljeno: 13.06.2018; Ogledov: 538; Prenosov: 43
.pdf Celotno besedilo (257,70 KB)
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An analysis of corruption in microenterprises
Mladen Tomašič, 2009, izvirni znanstveni članek

Opis: The purpose of this study is to present the research work made whilst studying the presence of corruption in the operations of Slovenian micro-enterprises. Our study builds on research which we carried out in 2005 and compares the findings of both studies. We wish to present our findings to public experts for a professional assessment and provide a basis for further work. We hope that in this way we can contribute to the development of new guidelines for the preparation of further analysis, the causes and elimination or at least limitation of corruption in business operations. Notable studies, which address corporate corruption in Slovenia, are non-existent. The results have confirmed the basic research hypothesis that the presence of corruption in the micro-business environment compared to a previous study in the last five years has increased.
Ključne besede: micro-enterprise, micro-entrepreneur, corruption, corruptness
Objavljeno: 28.11.2017; Ogledov: 362; Prenosov: 224
.pdf Celotno besedilo (1,09 MB)
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Awareness of cloud computing in Slovenian and Croatian micro-enterprises
Borut Werber, Marina Klačmer Čalopa, Igor Pihir, Anja Žnidaršič, 2015, izvirni znanstveni članek

Opis: This paper presents a comparison of the two studies conducted in Slovenian and Croatian micro-enterprises (µE) about the awareness of the cloud computing (CC). We were interested in the issues relating to the characteristics of µE and the latter's use of information and communication technology (ICT) in business processes. Also, the characteristics of owners and µE were investigated. We found that the results obtained in the two countries were similar. In both cases, the most important CC characteristics were reliability, security and performance. Given that CC could represent a good business opportunity for µE, some managerial implications are proposed.
Ključne besede: comparison, cloud computing, cloud computing services, micro-enterprise
Objavljeno: 03.08.2017; Ogledov: 482; Prenosov: 69
.pdf Celotno besedilo (868,57 KB)
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Influence of kinematic factors of friction stir welding on the characteristics of welded joints of forged plates made of EN AW 7049 A aluminium alloy
Milenko Perović, Sebastian Baloš, Dražan Kozak, Darko Bajić, Tomaž Vuherer, 2017, izvirni znanstveni članek

Opis: In this paper, the influence of rotation speed and welding speed on the impact strength, microstructure and cross section micro hardness of FSW welded joints of Al-Zn-Mg-Cu high strength aluminium alloy is studied. Rotation speed was varied from 750 min−1 to 850 min−1 and welding speed from 60 mm/min to 80 mm/min. It was found that the energy of crack propagation is up to three times higher than the energy of crack initiation. This ratio was found by testing the Charpy notched specimens taken from left and right from the weld centre, 4 mm from the notch in a direction opposite to a direction of welding. Micro hardness distribution in the nugget does not show large dissipation of value regardless if the measuring point is in the upper or lower section of the nugget. Weld microstructure characteristics and zones are clearly defined at the basis of grain size and material flow.
Ključne besede: dynamic recrystallization, friction stir welding, impact strength, micro hardness distribution
Objavljeno: 12.07.2017; Ogledov: 614; Prenosov: 285
.pdf Celotno besedilo (2,13 MB)
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Compression pre-stress of tubular torsion springs
Vinko Močilnik, Nenad Gubeljak, Jožef Predan, Jože Flašker, 2010, izvirni znanstveni članek

Opis: This paper reports the results of a series of biaxial static compression and torsion experiments performed to evaluate the effects of static compression stress on the fatigue life of those smooth tubes made of high strength spring steel. The fatigue life of biaxial loaded springs depends, among others, on biaxial compression and torsion loading. A high shear loading ratio leads to low-cycle fatigue behaviour rather than high-cycle fatigue, because it was found that a crack was initiated at a local highly deformed area on surface of the specimen.The experimentally obtained results show a significant extension of fatigue strain life as a result of combining axial compression loading with torsion. Cracking behaviour was observed and it was noted that compression pre-stresses contribute to retardation of the fatigue crack initiation process and, consequently, contribute to the extension of fatigue life.
Ključne besede: fatigue, fatigue life, micro crack, multi axial stress state, pre-stressing, torsion, torsion bar springs, twist angle
Objavljeno: 11.07.2017; Ogledov: 424; Prenosov: 72
.pdf Celotno besedilo (1,10 MB)
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Quality and delivery of milk in Slovenia
Marjan Janžekovič, Maksimiljan Brus, Lidija Mužerlin, 2007, izvirni znanstveni članek

Opis: Milk production represents the possibility of earning monthly income and assures social security to many farms in Slovenia. In Slovenia the European rules and regulations on the quality of the delivered milk have been introduced, relating to the hygienic quality of milk and the count of somatic cells. The purchase price of the milk depends also on the protein and fat content. The aim of the research was to establish, whether the quality of the delivered milk complies with the prescriptions regulated by the Slovene legislation. The quality of the delivered milk in the area of the Šentjur agricultural cooperative (ACŠ) and in the entire area of Slovenia (SLO) has been studied. The bacteriological data in the individual quality classes, the data on the total count of somatic cels and the data on the fat and protein contents have been analyzed. 36 monthly accounts have been included in statistical processing. It has been established that the delivered milk of the areas in question does not differ in the relevant quality values.
Ključne besede: cattle, milk quality, fats, proteins, micro-organisms, somatic cells
Objavljeno: 10.07.2017; Ogledov: 523; Prenosov: 89
.pdf Celotno besedilo (337,54 KB)
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Fatigue crack initiation from microstructurally small Vickers indentations
Tomaž Vuherer, Andrej Godina, Zijah Burzić, Vladimir Gliha, 2007, izvirni znanstveni članek

Opis: The resistivity of coarse grain steel against crack initiation in the presence of micro defects is discussed. Samples of material with martensitic microstructure were prepared by adequate thermal treatment. Microstructurally small Vickers indentations were used as an artificial micro defect. The compressive residual stresses are due to the irreversibility of plastic deformation. The moment of indenting enables to prepare samples with and without effects of residual stresses. The stress level for crack initiation depends on the actual indentation size. The location of initiated cracks is affected by the presence and character of residual stresses.
Ključne besede: welded joints, micro defect, coarse grain HAZ, crack initiation, crack growth, stress concentration, fatigue limit, Vickers, residual stresses
Objavljeno: 03.07.2017; Ogledov: 608; Prenosov: 82
.pdf Celotno besedilo (1,02 MB)
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Monitoring the evaporation of fluids from fiber-optic micro-cell cavities
Eyal Preter, Borut Preložnik, Vlada Artel, Chaim Sukenik, Denis Đonlagić, Avi Zadok, 2013, izvirni znanstveni članek

Opis: Fiber-optic sensors provide remote access, are readily embedded within structures, and can operate in harsh environments. Nevertheless, fiber-optic sensing of liquids has been largely restricted to measurements of refractive index and absorption spectroscopy. The temporal dynamics of fluid evaporation have potential applications in monitoring the quality of water, identificationof fuel dilutions, mobile point-of-care diagnostics, climatography and more. In this work, the fiber-optic monitoring of fluids evaporation is proposed and demonstrated. Sub-nano-liter volumes of a liquid are applied to inline fiber-optic micro-cavities. As the liquid evaporates, light is refracted out of the cavity at the receding index boundary between the fluid and the ambient surroundings. A sharp transient attenuation in the transmission of light through the cavity, by as much as 50 dB and on a sub-second time scale, is observed. Numerical models for the transmission dynamics in terms of ray-tracing and wavefront propagation are provided. Experiments show that the temporal transmission profile can distinguish between different liquids.
Ključne besede: fiber-optic sensors, opto-fluidics, evaporation monitoring, optical micro-cells, fiber cavities, droplet analysis
Objavljeno: 22.06.2017; Ogledov: 466; Prenosov: 254
.pdf Celotno besedilo (551,58 KB)
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