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1.
On the integrability of persistent quadratic three-dimensional systems
Brigita Ferčec, Maja Žulj, Matej Mencinger, 2024, izvirni znanstveni članek

Opis: We consider a nine-parameter familiy of 3D quadratic systems, �˙=�+�2(�,�,�), �˙=−�+�2(�,�,�), �˙=−�+�2(�,�,�), where �2,�2,�2 are quadratic polynomials, in terms of integrability. We find necessary and sufficient conditions for the existence of two independent first integrals of corresponding semi-persistent, weakly persistent, and persistent systems. Unlike some of the earlier works, which primarily focus on planar systems, our research covers three-dimensional spaces, offering new insights into the complex dynamics that are not typically apparent in lower dimensions.
Ključne besede: ordinary differential equations, three-dimensional systems, integrability problem, persistent systems
Objavljeno v DKUM: 23.05.2024; Ogledov: 26; Prenosov: 3
.pdf Celotno besedilo (334,34 KB)
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2.
Sustainable design of circular reinforced concrete column sections via multi-objective optimization
Primož Jelušič, Tomaž Žula, 2023, izvirni znanstveni članek

Opis: An optimization model for reinforced concrete circular columns based on the Eurocodes is presented. With the developed optimization model, which takes into account the exact distribution of the steel reinforcement, which is not the case when designing with conventional column design charts, an optimal design for the reinforced concrete cross section is determined. The optimization model uses discrete variables, which makes the results more suitable for actual construction practice and fully exploits the structural capacity of the structure. A parametric study of the applied axial load and bending moment was performed for material cost and CO2 emissions. The results based on a single objective function show that the optimal design of the reinforced concrete column cross section obtained for the material cost objective function contains a larger cross-sectional area of concrete and a smaller area of steel compared with the optimization results when CO2 emissions are determined as the objective function. However, the optimal solution in the case where the material cost was assigned as the objective function has much more reserve in axial load capacity than in the optimal design where CO2 was chosen as the objective function. In addition, the multi-objective optimization was performed to find a set of solutions that provide the best trade-offs between the material cost and CO2 emission objectives.
Ključne besede: reinforced concrete columns, circular cross section, costs, CO2 emissions, multi-objective optimization, genetic algorithm
Objavljeno v DKUM: 15.04.2024; Ogledov: 169; Prenosov: 198
.pdf Celotno besedilo (4,56 MB)
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3.
Comparative analysis of direct operating costs: Conventional vs. hydrogen fuel cell 19-seat aircraft
Maršenka Marksel, Anita Prapotnik Brdnik, 2023, izvirni znanstveni članek

Opis: In this paper, a comparative analysis of direct operating costs between a 19-seat conventional and hydrogen-powered fuel cell aircraft is performed by developing a model to estimate direct operating costs and considering the evolution of costs over time from 2030 to 2050. However, due to the technology being in its early stages of development and implementation, there are still considerable uncertainties surrounding the direct operating costs of hydrogen aircraft. To address this, the study considers high and low kerosene growth rates and optimistic and pessimistic development scenarios for hydrogen fuel cell aircraft, while also considering the evolution of costs over time. The comparative analysis uses real flight and aircraft data for the airliner Trade Air. The results show that the use of 19-seat hydrogen fuel cell aircraft for air transportation is a viable option when compared to conventional aircraft. Additionally, the study suggests potential policies and other measures that could accelerate the adoption of hydrogen fuel cell technology by considering their direct operating costs.
Ključne besede: fuel cell aircrafts, direct operating cost of aircraft, 19-seat aircraft
Objavljeno v DKUM: 15.04.2024; Ogledov: 87; Prenosov: 6
.pdf Celotno besedilo (522,50 KB)
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Carbonization of Class G well cement containing metakaolin under supercritical and saturated environments
Gregor Kravanja, Željko Knez, 2023, izvirni znanstveni članek

Ključne besede: well cement, carbonization, metakaolin, supercritical CO2, gas saturated solution, CaCo3
Objavljeno v DKUM: 15.04.2024; Ogledov: 86; Prenosov: 3
.pdf Celotno besedilo (14,25 MB)
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7.
Impact of the Hydroelectric Dam on Aquifer Recharge Processes in the Krško Field and the Vrbina Area : Evidence from Hydrogen and Oxygen Isotopes
Branka Trček, Beno Mesarec, 2023, izvirni znanstveni članek

Opis: The impact of the damming of the Sava river for the Brežice hydroelectric power plant on the rise of the groundwater level was studied in the intergranular aquifer of the Krško field and the Vrbina area, Slovenia. The study is based on the application of hydrogen and oxygen isotopes (18O, 2H and 3H). Parameters were determined for precipitation, surface water, and groundwater for periods before and after the filling of the accumulation basin, with the aim of evaluating the groundwater–surface water interaction and to elucidate the impact of the hydroelectric dam on aquifer recharge processes. The results show the proportions of the surface water component in groundwater sampled from four wells at high and low water conditions, separately for the period before and after the filling the accumulation basin. After filling the accumulation basin, the proportion of the Sava river component at high water conditions increased from 60% to 80% in the Brege and Drnovo wells (drinking water resources), from 50% to 80% in the Cerklje well and to almost 100% in the near-river NEK well. Combined with previous studies, the results provide important information about the direction of groundwater flow in the aquifer and improve the conceptual model of the study site.
Ključne besede: stable isotopes, tritium, dam, surface water, groundwater
Objavljeno v DKUM: 28.03.2024; Ogledov: 105; Prenosov: 6
.pdf Celotno besedilo (28,81 MB)
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8.
Logistika za prometne inženirje
Tomislav Letnik, 2024, univerzitetni, visokošolski ali višješolski učbenik z recenzijo

Opis: Uvod učbenika se posveča temeljnim pojmom, ki so potrebni za razumevanje področja logistike, in aktualnim logističnim izzivom. Skozi nadaljevanje so predstavljene bistvene sestavine logističnega sistema, njegove funkcije in pomen logistike za delovanje družbe. Poseben poudarek je namenjen logistiki v poslovnih procesih, povezanih z nabavo, proizvodnjo, prodajo in poprodajnimi ter razbremenilnimi vidiki. Opisani in razloženi so vidiki upravljanja logističnih procesov, pri čemer je poseben poudarek na oskrbovalnih verigah in mestni logistiki. Zadnji del učbenika je namenjen prihodnjemu razvoju logistike, pri čemer so podrobneje opisani procesi fizičnega interneta. Na koncu vsakega poglavja so zastavljena vprašanja, ki spodbujajo kritični razmislek z željo, da študentje raziskujejo področje logistike preko mej tega učbenika.
Ključne besede: tovorni transport, skladiščenje, oskrbovalna veriga, fizični internet, logistika
Objavljeno v DKUM: 27.03.2024; Ogledov: 163; Prenosov: 19
.pdf Celotno besedilo (20,68 MB)
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9.
Numerical analysis of the racking behaviour of multi-storey timber-framed buildings considering load-bearing function of double-skin façade elements
Miroslav Premrov, Erika Kozem Šilih, 2023, izvirni znanstveni članek

Opis: The paper presents an innovative approach in the modelling of multi-storey timber-framed buildings, where double-skin façade elements (DSF) are additionally considered as load-bearing wall elements against a horizontal load impact. The mathematical model with a fictive diagonal element developed for timber-framed wall elements with classical oriented strand boards (OSB) or fibre–plaster sheathing boards (FPB) is upgraded for DSF elements. The diameter of the fictive diagonal is determined with either experimental results or numerically obtained results using the time-consuming FEM model with elastic spring elements, which simulates the bonding line between the timber frame and both glazing panes. In the second part of the study, the numerical analysis of a specially selected three-storey timber-framed building was performed using the developed mathematical model with fictive diagonal elements. Two alternative calculations were performed with the DSF elements as non-resisting and racking-resisting wall elements. It was demonstrated on the selected case that the racking resistance (R) of a building can essentially increase up to 35% if DSF elements are considered as resisting wall elements. As a secondary goal of the study, it is also important to point out that by using DSF elements as racking-resisting elements, the distortion in the first floor essentially decreased. It is demonstrated on the selected numerical example that this torsional influence decreased notably (by almost 18%) when the load-bearing DSF elements were used for seismic excitation in the X direction. Therefore, such an approach can open new perspectives in designing multi-storey timber-framed buildings with a more attractive and dynamic floor plan and structure.
Ključne besede: sustainability, timber, structures, multi-storey, numerical analysis, DSF, racking resistance
Objavljeno v DKUM: 19.03.2024; Ogledov: 125; Prenosov: 19
.pdf Celotno besedilo (4,93 MB)
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10.
Dimenzioniranje armiranobetonskih konstrukcij po metodi mejnih stanj
Peter Dobrila, 2024

Opis: Publikacija predstavlja zelo obširen spekter dimenzioniranja armirano-betonskih (AB) elementov, tako linijskih, kot ploskovnih elementov. Posamična poglavja so tematsko zasnovana tako, da so najprej predstavljene osnovne teoretične osnove osnovnih mehanskih mehanizmov posameznega obremenitvenega problema konstrukcijskih elementov, v drugem delu pa nato še aplikacije na specifični primer uporabe veljavnih Evrokod standardov. V posameznih poglavjih so na koncu podani tudi posebni konkretni računski primeri, ki bralcu približajo uporabo Evrokod standardov na posameznih izbranih vzorčnih primerih. Dodatno pa bo publikacija lahko zelo koristen učni in uporabniški pripomoček tudi za projektante armirano-betonskih konstrukcij v projektivnih birojih, ter v določeni meri tudi za izvajalce gradbenih del. Publikacija je sicer tematsko razdeljena v 14 ločenih samostojnih poglavij.
Ključne besede: beton, konstrukcije, mehanika konstrukcij, evrokod standardi, metoda mejnih stanj
Objavljeno v DKUM: 15.03.2024; Ogledov: 280; Prenosov: 29
.pdf Celotno besedilo (16,82 MB)
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