1621. Evaluation of ash pozzolanic activity by means of the strength activity index test, frattini test and DTA/TG analysisSabina Dolenec, Vilma Ducman, 2018, original scientific article Abstract: The pozzolanic activity of five different types of ash was studied using various direct and indirect methods. In addition to strength activity index (SAI) determination and the Frattini test, ash pozzolanicity was assessed via differential thermal and thermogravimetric analyses (DTA/TG) after curing for 7, 28 and 90 days. The results showed that, due to their respective mineralogical, chemical and physical characteristics, the ashes exhibited different levels of pozzolanic activity in terms of the amount of lime with which they could chemically bind, as well as reaction kinetics. Although SAI and Frattini test results were not in agreement in the case of some of the ashes, DTA/TG analysis revealed that a certain amount of portlandite was consumed, thus confirming the occurrence of a pozzolanic reaction. The results also showed that ashes with higher amounts of reactive SiO2 were more reactive, while those with higher BET surface areas displayed a faster pozzolanic reaction rate.
Keywords: biomass ash, DTA/TG, fly ash, Frattini test, pozzolanic activity, SAI
Published in DiRROS: 11.12.2023; Views: 300; Downloads: 148
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1622. Revitalised geotourism mining heritage potentials in the Posavje FoldsMateja Golež, 2018, original scientific article Abstract: The territory of the Posavje Folds offers many geotourism potentials reflecting in particular in rich mining heritage. For a long time, local communities have considered them mainly in the context of local problems, but nowadays we may see individual examples of successful revitalization of cave chambers and mining structures. All that has given rise to fantastic stories about the mining wealth of the underground world and the mining heritage interpreted with modern approaches and new findings. In addition to managers and heritage owners, the revitalization process also includes scientists, artists, architects and educators who, each in their own way, contribute to a holistic perspective of the values of the past in light of contemporary understanding of this type of heritage. As a result, the territory has witnessed the revitalization of the medieval lead and silver mine Padež pri Laškem, the former Laško coal mine machine room, which was transformed into the Strojnica Gallery, and the polymineral mine Sitarjevec within the last five years. All mentioned examples are cases of abandoned mining activities with long-lasting mining tradition, which left an imprint in the area in terms of the diverse social structure of the population and in terms of town development, which also allows us to evaluate from a distance the contribution to the construction of the railway between Vienna and Trieste, which put these towns on the European map of centres of industrial significance in the mid-19th century. Trains that still connect the Austrian capital with the Adriatic coast may in future, in light of sustainable green tourism, attract curious guests to stop and linger a while, which is the ultimate goal of the attempts of local communities to revitalise mining heritage. Meanwhile, the goals set can only be realised with the help of new and attractive tourist products that reflect own creativity related with tradition ranging from design ideas, music events, art installations, popular science evenings; in short, with contents that are suited to visitors of all ages.
Keywords: mines, heritage, revitalisation, geoturism
Published in DiRROS: 11.12.2023; Views: 302; Downloads: 118
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1623. Quantified joint surface description and joint shear strength of small rock samplesKarmen Fifer Bizjak, Andraž Geršak, 2018, original scientific article Abstract: Geotechnical structures in rock masses such as tunnels, underground caverns, dam foundations and rock slopes often have problems with a jointed rock mass. The shear behaviour of a jointed rock mass depends on the mechanical behaviour of the discontinuities in that particular rock mass. If we want to understand the mechanical behaviour of a jointed rock mass, it is necessary to study the deformation and strength of a single joint. One of the primary objectives of this work is to improve the understanding of the frictional behaviour of rough rock joints under shear loads with regard to the roughness of the joint surface. The main problem is how to measure and quantify the roughness of the surface joint and connect the morphological parameters into a shear strength criterion. Until now, several criteria have been developed; however, all of them used large rock samples (20×10×10 cm). It is often not possible to get large samples, especially when the rock is under a few meters thick layer of soil. In this case, samples of rock can only be acquired with investigation borehole drilling, which means that the samples of rock are small and of different shapes. The paper presents the modified criterion that is suitable for calculating the peak shear stress of small samples.
Keywords: camera-type 3D scanner, rock mechanics rock joint, roughness of the joints, rock joint shear strength
Published in DiRROS: 11.12.2023; Views: 330; Downloads: 148
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1624. Pathway toward sustainable winter road maintenance (case study)Katja Malovrh Rebec, Janez Turk, 2023, independent scientific component part or a chapter in a monograph Abstract: Life Cycle Assessment (LCA) method was applied to evaluate the environmental impacts of winter road maintenance managed by an innovative road-weather information system and the impacts of vehicles passing the road during the snowstorm event. A case study refers to 10-hour lasting snowstorm event, considering a specific road section and application of a road-weather information management system to help winter road maintenance agency optimizing activities (salt gritting and/or plowing). Reliable information on the timing of the beginning of the snowstorm event affects (1) the activities of winter road maintenance, (2) the mobility of all vehicles passing the road, and (3) the fuel consumption of the vehicles. Since activities are optimized in case of preventive operation of winter road maintenance, less salt is needed overall. The road remains free of snow cover in case of preventive winter road maintenance operation, meaning that passenger cars and trucks pass the road at normal speed, without undesirable acceleration and braking caused by wheels slipping if snow accumulates on the road. Fuel consumption of vehicles passing salted and snow-free road remains unchanged, while fuel consumption increases in case of snow cover. Reduction of environmental burdens in case of such optimized winter road maintenance operation, is shown in this case study. The overall results of the comparative LCA analysis showed that the use of the road-weather information system in road traffic allows for as much as 25% reduction of environmental footprints. In the scenario where the winter service does not use information system the winter service also uses 40% more salt, which is also related with additional environmental impacts.
Keywords: LCA, okoljski odtisi, cesta, snežne razmere, preventivno delovanje, promet, poraba goriva, varnost, LCA, environmental impacts, road, snow cover, preventive operation, traffic, fuel consumption, safety
Published in DiRROS: 11.12.2023; Views: 275; Downloads: 168
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1625. Experimental study and thermodynamic modelling of the temperature effect on the hydration of belite-ye’elimite-ferrite cementsMaruša Mrak, Frank Winnefeld, Barbara Lothenbach, Andraž Legat, Sabina Dolenec, 2024, original scientific article Abstract: This study focuses on the kinetics of hydration, phase assemblage, microstructure and mechanical properties after various hydration times of two different BCSA cements at 5, 20, 40 and 60 ◦C and compares experimental data with thermodynamic modelling. Different curing temperatures change the type of hydrates and their amounts. Ye’elimite and gypsum in belite-ye’elimite-ferrite cements are almost fully reacted after 24 h of hydration at 20, 40 and 60 ◦C, while not at 5 ◦C. The hydration of belite is slower than the one of ye’elimite, but reaches a high degree of hydration after 150 days which is increasing with temperature. Less ettringite is present at elevated temperatures due to its increasing solubility, while more monosulfate is observed. Furthermore, with increasing temperature siliceous hydrogarnet forms at the expenses of strätlingite as well as more C S H is found as more belite reacts resulting in higher compressive strength. Dense and homogenous microstructure is observed at 5 ◦C, while it is more heterogeneous at higher temperatures. The presence of more ye’elimite resulted in higher ettringite and str¨atlingite formation and a higher compressive strength, while more belite yields more C S H in the hydrates and lower compressive strength.
Keywords: belite-ye’elimite-ferrite cement, temperature, hydration, thermodynamic modelling
Published in DiRROS: 11.12.2023; Views: 277; Downloads: 212
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1626. Coastal flood risk assessment : an approach to accurately map flooding through national registry-reported eventsErik Kralj, Peter Kumer, Cécil J. W. Meulenberg, 2023, original scientific article Keywords: sea flood prediction, flooding maps, climate change resilience, natural disaster registry, coastal inundation, flood-prone areas
Published in DiRROS: 08.12.2023; Views: 412; Downloads: 162
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1628. Zagotavljanje kakovosti v ultrazvočni diagnostikiSašo Rainer, 1999, review article Abstract: Izvajanje programa za zagotavljenje kakovosti ima velik pomen tudi v ultrazvočni diagnostiki, saj lahko poslabšanje kakovosti slike in nekaterih funkcij pomembno vpliva na zmožnost odkrivanja in pravilne opredelitve patoloških procesov. Elementi programa za zagotavljanje kvalitete so: pravilnoravnanje z aparaturo, njeno dnevno vzdrževanje, detekcija slabšanja kakovosti pri dnevnem delu in redno testiranje vsakih šest mesecev. Testiranjezajema vizualno inspekcijo aparature (sond, mehaničnih delov, filtra, kablov in kontaktov), oceno kakovosti dokumentacijskih posnetkov, testiranje s fantomom in dokumentacijo rezultatov. S fantomom preverjamo specifične parametre, ki neposredno zadevajo kakovost slike. V prispevku so okvirno obrazloženi ti parametri ter njihov pomen, opisane so tudi vrste ultrazvočnih fantomov. Redno izvajanje programa za zagotavljanje kakovosti bi moralo postati obvezen sestavni del aktivnosti vsake ultrazvočne diagnostične enote.
Published in DiRROS: 08.12.2023; Views: 280; Downloads: 49
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1629. Tehnične zahteve kakovostnega ultrazvočnega aparataSašo Rainer, 1999, professional article Abstract: Ultrazvočna tehnologija doživlja skokovit razvoj; spreminjajo se tudi merila glede kakovosti ultrazvočnih aparatur.Aparat naj bo zasnovan na osnovi digitalne tehnologije, saj le-ta prinaša številne prednosti. Za preiskave dojkuporabljamo visokofrekventne linearne sonde, najbolje multifrekventne (med5- in 12 MHz), k osnovni opremi pa sodijo tudi konveksne in sektorske sonde (med 3- in 5- MHz). Vse sonde naj omogočajo dopplersko funkcijo. Pribor naj vsebuje kakovostno vodilo za punkcije. Aparatura naj omogoča spektralni (pulzni) doppler, barvni doppler in angio- oziroma power doppler; zaznava naj čim nižje pretoke. Dinamični obseg naj bo čim večji.Pomemben je dovolj velik notranji spomin. Najpogosteje uporabljene nastavitve naj bodo shranjene v obliki programov (preset). Barvni monitor mora imeti visoko ločljivost. Kontrolna plošča mora biti zasnovana ergonomsko. Naštete so možnosti za dokumentacijo posnetkov. Aparatura naj omogoča povezavo v računalniška omrežja(kompatibilnost s standardom Dicom 3,0)
Published in DiRROS: 08.12.2023; Views: 271; Downloads: 48
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1630. Mamografska tehnika - projekcije in kompresijaKristijana Hertl, Miljeva Rener, 1999, review article Abstract: Vsaka od različnih projekcij pri slikanju dojk doda svoj pomemben delež k prepoznavanju začetnega karcinoma dojke. Zelo pomembna je tudi pravilna in zadostna kompresija pri slikanju dojk. Nepravilno izvedena projekcija in kompresija lahko že ob prvem slikanju zavedeta radiologa k lažno negativnem izvidu, kar pa za ženo pomeni zakasnitev terapije in bistveno poslabša prognozo. Radiološki inženir in radiolog se morata zavedati, da z določeno projekcijo dobro prikažemo samo določene dele dojke. Pogoj za optimalen prikaztkiva dojke je prepoznavanje anatomskih odnosov med prsno steno, pektoralno mišico in žleznim tkivom.
Published in DiRROS: 08.12.2023; Views: 383; Downloads: 72
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