71. Vpliv vpetosti med preiskavo obnašanja nearmiranih zidov pri potresni obtežbiPetra Triller, Matija Gams, Miha Tomaževič, 2020, original scientific article Abstract: V prispevku so predstavljene obsežne eksperimentalne raziskave obnašanja večetažnih zidanih strižnih sten z odprtinami pri potresni obtežbi. Preiskali smo odziv 3-etažnega preizkušanca v naravnem merilu na potresno obtežbo, s katero smo preučevali odziv tipične 5-etažne zidane stavbe, grajene na območju Slovenije in njene širše okolice v času pred letom 1964 (pred prvimi potresni predpisi). Vzporedno smo opravili osem cikličnih strižnih preiskav posameznih zidov pri štirih tipih robnih pogojev. Z analizo rezultatov obsežnih meritev sil in deformacij na površini večetažnih strižnih sten smo ovrednotili vpliv vertikalnih in horizontalnih elementov strižne stene na posamezni slop ter iskali najustreznejši tip robnih pogojev za simulacijo potresnega odziva v preiskavi posameznega zidnega slopa.
Keywords: nearmirano zidovje, ciklične strižne preiskave, opečni votlak, preiskava v naravnem merilu, optični sistem za merjenje deformacij
Published in DiRROS: 05.09.2023; Views: 316; Downloads: 119
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72. Quality control of thermally modified timber using dynamic vapor sorption (DVS) analysisMiha Humar, Rožle Repič, Davor Kržišnik, Boštjan Lesar, Romana Cerc Korošec, Christian Brischke, Lukas Emmerich, Gregor Rep, 2020, original scientific article Abstract: The importance of thermal modification is increasing worldwide. Increased use of thermally modified timber (TMT) has resulted in a need for reliable quality control, comprising control of variation of the production within defined limits, allowing third-party control in the case of certification and the regulation of customer complaints and claims. Techniques are thus needed to characterise the modification of quality in terms of improved target properties of TMT during industrial production, and of TMT products that have been in service for an arbitrary time. In this study, we aimed to utilise dynamic vapor sorption (DVS) for this purpose. Norway spruce (Picea abies) and European beech (Fagus sylvatica) samples were thermally modified at different temperatures according to different heat treatment techniques: (1) the Silvapro process based on an initial vacuum; (2) an air heat treatment, whereby samples were wrapped in aluminium foil; (3) thermal modification of wood samples in the ambient atmosphere in a laboratory oven. Wood samples from closed processes were analysed for validation. TMT was characterised with respect to mass loss, colour and density. Mass loss of wood due to modification (MLTM) was correlated with factors derived from DVS analysis. The present DVS measurements suggest that the equilibrium wood moisture content (EMC95% RH), the time to reach 10% wood moisture content (t10% MC), and the elongation factor, c, derived from a logarithmic function, can serve as alternative parameters to characterise the quality of several thermal modification processes. Further studies are recommended using other wood species, different modification processes and further parameters gained from DVS measurements to understand the robustness and the predictive power of the applied technique
Keywords: thermal modification, quality control, dynamic vapour sorption, wood, moisture content
Published in DiRROS: 31.08.2023; Views: 382; Downloads: 181
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73. Analiza ključnih vzrokov smrtnosti rjavega medveda (Ursus arctos L.) v Sloveniji v obdobju zadnjih 6 let (1.4.1991-31.3.1997)Miha Adamič, 1997, original scientific article Keywords: rjavi medved, mortaliteta, analiza, vzrok, lov, trofeja, trofejni odstrel, promet
Published in DiRROS: 28.08.2023; Views: 454; Downloads: 122
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74. Corrosion behavior of steel in pore solutions extracted from different blended cementsMiha Hren, Tadeja Kosec, Andraž Legat, 2020, original scientific article Abstract: Mortar specimens made from four different types of cement, CEM I, CEM II, CEM III, and CEM IV, were prepared and pore solutions extracted. Three different types of exposure were studied: noncarbonated without chlorides, noncarbonated with chlorides, and carbonated with chlorides. Various electrochemical methods (linear polarization, potentiodynamic polarization measurements) were implemented to characterize the processes of corrosion on steel in these solutions. The type and extent of corrosion products were evaluated by means of various spectroscopic techniques. Specific differences in the type and extent of corrosion damage were determined and compared for each of the extracted pore solutions from the different blended cements. An attempt was made to classify these differences in comparison with the reference cement (CEM I) and in relation to the different types of exposure.
Keywords: corrosion, steel in pore water, blended cements, Raman Spectroscopy
Published in DiRROS: 22.08.2023; Views: 360; Downloads: 174
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75. Validation of combinatorial evaluation of strain-gauge amplifier linearityMiha Hiti, 2020, original scientific article Abstract: This paper describes a validation of a combinatorial calibration technique based calibration procedure for strain-gauge amplifier calibration. The deviation between two strain-gauge amplifiers at calibration using the combinatorial technique is compared to the deviation between the same two amplifiers at calibration on a force calibration machine as a transducer-amplifier chain under unchanged conditions, serving as an amplifier linearity comparator. This enables the validation to be confirmed with a suitable expanded measurement uncertainty of 3 nV/V.
Keywords: strain-gauge amplifier, calibration, combinatorial technique, validation
Published in DiRROS: 21.08.2023; Views: 361; Downloads: 119
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76. Upper Miocene ostracods from the Krško Basin, SE SloveniaMiha Marinšek, Valentina Hajek-Tadesse, Marijan Poljak, Tea Kolar-Jurkovšek, Luka Gale, 2023, original scientific article Abstract: The purpose of this study was to identify the ostracod assemblage from a 43 m thick section of
the Bizeljsko Formation, which constitutes the middle part of the Upper Miocene Posavje Group.
The succession comprises sandstone, siltstone, and marlstone, deposited in a delta front environment. The determined ostracods belong to the families Cyprididae, Cytheridae, Darwinulidae, and Loxoconchidae. In total, 30 species were identified. Additionally, 8 morphotypes were determined at the genus level. The most common genera are Candona, Hemicytheria, and Cyprideis. The assemblage belongs to the Caspiocypris labiata subzone from the upper Pannonian.
The ostracod assemblage from the Krško Basin is similar in species composition to Pannonian ostracod assemblages from Croatia and Serbia.
Keywords: Lake Pannon, Bizeljsko Formation, Pannonian, biostratigraphy, palaeoenvironment
Published in DiRROS: 27.07.2023; Views: 353; Downloads: 164
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77. Environmentally friendly protection of European beech against fire and fungal decay using a combination of thermal modification and mineralisationRožle Repič, Andreja Pondelak, Davor Kržišnik, Miha Humar, Nataša Knez, Friderik Knez, Andrijana Sever Škapin, 2024, original scientific article Abstract: The demand for construction timber is continuously increasing, due to its favourable characteristics. However, the adequate protection of wood is key to its successful use, as it is flammable and susceptible to biodegradation. Given that thermal modification enhances the durability of wood, and mineralisation with CaCO3 considerably improves its fire properties, it is worth considering the combined effects of the two methods. European beech (Fagus sylvatica) was selected to determine the effects of a) thermal modification, b) mineralisation through the in-situ formation of CaCO3, and c) a combination of the two procedures, on resistance to decay fungi, reaction to fire and the mechanical properties of the wood. Microscopic analysis and comparisons of the samples before and after exposure to fungi were also conducted. Mineralised wood generally had a slightly alkaline pH value and higher equilibrium moisture content, while thermal modification lowered the equilibrium moisture content. The present study demonstrated the combined effect of thermal modification and mineralisation: the best response to fire as well as resistance to fungi was achieved when the two treatments were combined. Results from the Brinell hardness and three-point bending tests indicate that both modification procedures can slightly impair the mechanical properties of the wood.
Keywords: wood, protection, durability, mechanical properties
Published in DiRROS: 12.07.2023; Views: 405; Downloads: 288
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78. Sensor development for corrosion monitoring of stainless steels in H2SO4 solutionsMiha Hren, Tadeja Kosec, Mari Lindgren, Elina Huttunen-Saarivirta, Andraž Legat, 2021, original scientific article Abstract: Equipment made of different stainless steels is often used in the hydrometallurgical processing industry. In this study, an electrical resistance sensor was developed for monitoring corrosion in acidic solutions at high temperature. Two types of stainless steel were used as the electrode materials, namely grade 316L stainless steel (EN 1.4404) and grade 2507 duplex stainless steel (EN 1.4410). The materials and sensors were exposed to a 10% H2SO4 solution containing 5000 mg/L of NaCl at various temperatures. Results from the sensors were verified using electrochemical techniques and postexposure examination. Results showed that the microstructure played an important role in the interpretation of corrosion rates, highlighting the importance of using an appropriate stainless steel for the production of sensors. Electrochemical tests and postexposure examination both showed that the grade 2507 had a significantly lower corrosion rate compared to the grade 316L. Under industrial‑process conditions, the results for the grade 2507 sensor were promising with respect to sensor durability and performance, despite the extremely harsh operating environment.
Keywords: stainless steel, hydrometallurgical industry, sulphuric acid, electrical resistance sensor, corrosion
Published in DiRROS: 05.07.2023; Views: 399; Downloads: 204
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79. Characterizing steel corrosion in different alkali-activated mortarsNina Gartner, Miha Hren, Tadeja Kosec, Andraž Legat, 2021, original scientific article Abstract: Alkali-activated materials (AAMs) present a promising potential alternative to ordinary Portland cement (OPC). The service life of reinforced concrete structures depends greatly on the corrosion resistance of the steel used for reinforcement. Due to the wide range and diverse properties of AAMs, the corrosion processes of steel in these materials is still relatively unknown. Three different alkali-activated mortar mixes, based on fly ash, slag, or metakaolin, were prepared for this research. An ordinary carbon-steel reinforcing bar was installed in each of the mortar mixes. In order to study the corrosion properties of steel in the selected mortars, the specimens were exposed to a saline solution in wet/dry cycles for 17 weeks, and periodic electrochemical impedance spectroscopy (EIS) measurements were performed. The propagation of corrosion damage on the embedded steel bars was followed using X-ray computed microtomography (XCT). Periodic EIS measurements of the AAMs showed different impedance response in individual AAMs. Moreover, these impedance responses also changed over the time of exposure. Interpretation of the results was based on visual and numerical analysis of the corrosion damages obtained by XCT, which confirmed corrosion damage of varying type and extent on steel bars embedded in the tested AAMs.
Keywords: corrosion, alkali-activated mortars, steel reinforcement, electrochemical impedance spectroscopy, X-ray computed microtomography, visual analysis
Published in DiRROS: 05.07.2023; Views: 453; Downloads: 203
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