1611. Quantified joint surface description and joint shear strength of small rock samplesKarmen Fifer Bizjak, Andraž Geršak, 2018, izvirni znanstveni članek Povzetek: 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.
Ključne besede: camera-type 3D scanner, rock mechanics rock joint, roughness of the joints, rock joint shear strength
Objavljeno v DiRROS: 11.12.2023; Ogledov: 305; Prenosov: 130
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1612. Pathway toward sustainable winter road maintenance (case study)Katja Malovrh Rebec, Janez Turk, 2023, samostojni znanstveni sestavek ali poglavje v monografski publikaciji Povzetek: 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.
Ključne besede: LCA, okoljski odtisi, cesta, snežne razmere, preventivno delovanje, promet, poraba goriva, varnost, LCA, environmental impacts, road, snow cover, preventive operation, traffic, fuel consumption, safety
Objavljeno v DiRROS: 11.12.2023; Ogledov: 255; Prenosov: 160
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1613. 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, izvirni znanstveni članek Povzetek: 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.
Ključne besede: belite-ye’elimite-ferrite cement, temperature, hydration, thermodynamic modelling
Objavljeno v DiRROS: 11.12.2023; Ogledov: 249; Prenosov: 180
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1614. Coastal flood risk assessment : an approach to accurately map flooding through national registry-reported eventsErik Kralj, Peter Kumer, Cécil J. W. Meulenberg, 2023, izvirni znanstveni članek Ključne besede: sea flood prediction, flooding maps, climate change resilience, natural disaster registry, coastal inundation, flood-prone areas
Objavljeno v DiRROS: 08.12.2023; Ogledov: 381; Prenosov: 141
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1616. Zagotavljanje kakovosti v ultrazvočni diagnostikiSašo Rainer, 1999, pregledni znanstveni članek Povzetek: 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.
Objavljeno v DiRROS: 08.12.2023; Ogledov: 264; Prenosov: 46
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1617. Tehnične zahteve kakovostnega ultrazvočnega aparataSašo Rainer, 1999, strokovni članek Povzetek: 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)
Objavljeno v DiRROS: 08.12.2023; Ogledov: 257; Prenosov: 45
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1618. Mamografska tehnika - projekcije in kompresijaKristijana Hertl, Miljeva Rener, 1999, pregledni znanstveni članek Povzetek: 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.
Objavljeno v DiRROS: 08.12.2023; Ogledov: 341; Prenosov: 58
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1619. Zagotavljanje kakovosti pri razvijanju mamogramovLucijan Miklavčič, 1999, pregledni znanstveni članek Povzetek: Uporaba senzitometra in denzitometra za spremljanje učinkovitosti pri razvijanju filmov mora biti poznana ekipi, ki se ukvarja z zagotavljanjem kakovosti na področju radiologije, posebno pa v mamografiji. Prispevek uvaja bralca v osnove, ki so potrebne za razumevanje programa zagotavljenja kakovosti in spremljanja parametrov pri razvijanju mamografskih filmov.
Objavljeno v DiRROS: 08.12.2023; Ogledov: 280; Prenosov: 67
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1620. Klinična presoja kakovosti mamogramovMiljeva Rener, Kristijana Hertl, 1999, pregledni znanstveni članek Povzetek: Kakovosten mamogram prikaže kar največ tkiva dojke, je primerno ekponiran, kontrasten, ni zabrisan, z nizkim šumom, brez artefaktov in je narejen s sprejemljivo dozo sevanja. Končni videz mamograma je skupek raznih dejavnikov,od katerih so najpomembnejši sodoben mamografski aparat z optimalnonaravnano fotocelico in s sodobnim priborom; posebna pozornost velja postopku razvijanja. Dobro usposobljeno, posebej za to delo izobraženo osebje mora vzdrževati visoko kakovost, to pa pripomore k čim manjšemu številu zgrešenih in zapoznelih diagnoz.
Objavljeno v DiRROS: 08.12.2023; Ogledov: 279; Prenosov: 66
Celotno besedilo (674,07 KB) |
