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1.
Advancing nanofluid numerical modelling: A novel Euler–Lagrange method with experimental validation
Nejc Vovk, Blaž Kamenik, Elif Begum Elcioglu, Erdem Ozyurt, Ziya Haktan Karadeniz, Alpaslan Turgut, Jure Ravnik, 2025, izvirni znanstveni članek

Opis: We present a novel approach to numerical modelling of thermal nanofluids based on the Euler–Lagrange method. This approach overcomes the challenge of extremely fine temporal discretization, which previous Euler–Lagrange nanofluid numerical models struggled to address, while also avoiding the need for too many Lagrangian nanoparticles. A numerical uncertainty assessment method is adapted for the proposed approach. The model is validated with a simple verification case and applied to simulate a closed natural circulation loop heat exchanger operating with heating power ranging from 10 W to 50 W and nanoparticle volume fractions of 0.5% to 2%, using an Al2O3–water nanofluid. Results are compared with experimental temperature measurements and an Euler–Euler implementation of the same nanofluid. The model is also applied to simulate the natural convection inside a vertical enclosure, studied experimentally by other authors. The proposed novel approach demonstrates agreement with both experimental data and the Euler–Euler implementation, effectively capturing the overall behaviour of nanofluids. We establish, that the interplay of multiple transport phenomena, that occur in nanofluid operated devices, can be difficult to completely reproduce numerically within the framework of current modelling assumptions.
Ključne besede: Euler–Lagrange nanofluid modelling, numerical uncertainty assessment, natural convection loop simulation, nanoparticle concentration analysis, nanofluid heat transfer
Objavljeno v DKUM: 17.06.2025; Ogledov: 0; Prenosov: 3
.pdf Celotno besedilo (3,33 MB)
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2.
Use of a heating system to control the probiotic beverage production in batch bioreactor
Jožef Ritonja, Andreja Goršek, Darja Pečar, 2021, izvirni znanstveni članek

Opis: Fermentation is a crucial bioengineering process, existentially important for modern society. The most commonly used production unit for this process is the batch bioreactor. Its main advantage is unsophisticated construction, which unfortunately results in its incapability of controlling the transient state of the fermentation process. Control of the fermentation can significantly improve the quality of the product and the economy of the process; therefore, it is useful for bioreactors to be equipped with a control system. Based on the experimental results, we used an optimization method to identify a mathematical model that describes the impact of the bioreactor’s temperature on the fermentation’s transient process. The obtained model was applied for the design and synthesis of the closed-loop control system. Simulations and experiments confirmed the effectiveness of the proposed control system. In this way, we can ensure the consistent quality of the produced probiotic product, increase the amount of the product, and shorten the fermentation time. The original results display the feasibility of the closed-loop control of the batch bioreactor’s fermentation process by changing the temperature. So far, the process has been carried without a closed-loop control system. The problem is current and has not yet been solved sufficiently. There are many attempts published; one of the last shows the possibility of controlling the fermentation process by changing the oxygen supply, which is more complex and expensive for realization than the solution from our study.
Ključne besede: probiotic bewerages, fermentation, modelling, identification, control implementation
Objavljeno v DKUM: 16.06.2025; Ogledov: 0; Prenosov: 0
.pdf Celotno besedilo (2,79 MB)
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3.
Compression of triangulated solids’ surfaces by Decimating Reconstructable Triangles
Blaž Repnik, Borut Žalik, Krista Rizman Žalik, 2025, izvirni znanstveni članek

Opis: This paper introduces a new programming solution for reducing the size of files needed to store 3D geometric solids, whose surfaces are interpolated by watertight irregular triangle meshes. Unlike other approaches, the software does not introduce any special storage data format, but, instead, utilises popular CAD formats such as STL, OBJ, or PLY. This increases the software’s interoperability significantly. The software comprises an encoder and a decoder. The encoder estimates which facets may be removed in such a way that they can later be reconstructed unambiguously by the decoder. The decoder also ensures that the reconstructed triangles are oriented correctly. The encoder and the decoder are straightforward to understand and to implement. They are asymmetric, making any potential programming error easier to identify and correct.
Ključne besede: data compression, geometric modelling, computer-aided design, boundary representation, topology, watertightness
Objavljeno v DKUM: 30.05.2025; Ogledov: 0; Prenosov: 1
.pdf Celotno besedilo (2,71 MB)

4.
Analysis and synthesis of theoretical and practical implications of case management model and notation
Mateja Bule, Gregor Polančič, 2025, izvirni znanstveni članek

Opis: Case Management Model and Notation (CMMN) is a graphical notation used to model less predictable, highly flexible processes that may behave differently in each instance. It uses an event-centred approach and expands on what can be modelled with procedural modelling notations. Nearly a decade since the occurrence of CMMN, its practical use is questionable. We performed this research to identify possible reasons for this and to classify the potential advantages and disadvantages of CMMN. With the aforementioned objectives, we conducted a systematic literature review, which provided a broad insight into the state of the investigated object along with techniques for analysing qualitative data, coding, and successive approximation. From an initial set of 942 articles, 43 remain relevant. The results of the analysis and synthesis of the obtained data from relevant articles were generalised codes, which were used to explicitly answer the research questions. The results indicate that CMMN has good foundations in the declarative modelling approach and within the Case Management paradigm. Nevertheless, some issues were identified with the notation and elements of CMMN and with its complement—Business Process Model and Notation (BPMN).
Ključne besede: CMMN, case management, BPMN, declarative modelling, flexibility, visual language
Objavljeno v DKUM: 23.04.2025; Ogledov: 0; Prenosov: 1
.pdf Celotno besedilo (1,00 MB)

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A computational model for analysing the wear behaviour of polymer gears
Aljaž Ignatijev, Srečko Glodež, Aleš Belšak, Matej Borovinšek, 2025, izvirni znanstveni članek

Opis: In the presented study, a computational model was developed to analyse the wear behaviour of contacting mechanical elements like gears, bearings, etc. The model was built in the framework of the PrePoMax open-source CalculiX FEM (Finite Element Method) solver and enables a detailed analysis of the meshing dynamics of contacting mechanical elements. The model also considers the hyperelastic behaviour of the material in contact and the impact of operating temperature. The developed computational model was evaluated on a spur gear pair, where the pinion made of POM (Polyoxymethylene) was meshed with a support gear made of case-hardened steel 16MnCr5. The computational results were compared with the analytical results according to the VDI 2736 guidelines and experimental results on the real gear pairs. Compared to the standardised procedure according to the VDI 2736 guidelines, the model's main advantage is the geometry updating after a chosen number of loading cycles, enabling a more accurate prediction of wear behaviour under rolling/sliding loading conditions.
Ključne besede: wear, polymer gears, computational modelling, experimental testing
Objavljeno v DKUM: 08.04.2025; Ogledov: 0; Prenosov: 9
.pdf Celotno besedilo (5,53 MB)
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7.
Solidification of gelatine hydrogels by using a cryoplatform and its validation through CFD approaches
Yasir Beeran Potta Thara, Miha Jordan, Timi Gomboc, Blaž Kamenik, Boštjan Vihar, Vanja Kokol, Matej Zadravec, 2022, izvirni znanstveni članek

Opis: In this work, we developed a numerical approach based on an experimental platform to determine the working conditions on a cryoplatform and to predict and evaluate the cryogenic printing of hydrogels. Although hydrogels have good biocompatibility, their material properties make it difficult to print them with high precision and shape fidelity. To overcome these problems, a cryogenic cooling platform was introduced to accelerate the physical stabilisation of each deposited layer during the printing process. By precisely controlling solidification (crystallisation), each printed material can withstand its own weight to maintain shape fidelity, and the porosity of the scaffolds can also be controlled more selectively. The thermophysical properties of gelatine hydrogels were investigated to gain a better understanding of the phase change upon freezing. The corresponding material properties and experimental observations of gelatine solidification served as the basis for developing a computational fluid model (CFD) to mimic the solidification of gelatine hydrogels using a cryoplatform at different process conditions and extruder speeds. The goal was to develop a tool simple enough to predict acceptable process conditions for printing gelatine hydrogels using a cryoplatform.
Ključne besede: gelatine, hydrogel, cryoprinting, CFD simulation, solidification modelling
Objavljeno v DKUM: 20.03.2025; Ogledov: 0; Prenosov: 7
.pdf Celotno besedilo (5,41 MB)
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8.
Numerical study on in-plane behaviour of light timber-framed wall elements under a horizontal load impact
Miroslav Premrov, Erika Kozem Šilih, 2025, izvirni znanstveni članek

Opis: This study analyses the many different parameters of the in-plane flexibility problem regarding the lateral behaviour of light timber-framed (LTF) wall elements with different types of sheathing material (FPB, OSB, or even reinforced concrete), as well as the thickness of the timber frame elements (internal or external wall elements). The analysis simultaneously considers bending, shear, and timber-to-framing connection flexibility, while assuming stiff-supported wall elements as prescribed by Eurocode 5. Particular emphasis is placed on the sliding deformation between sheathing boards and the timber frame, which can significantly reduce the overall stiffness of LTF wall elements. The influence of fastener spacing (s) on sliding deformation and overall stiffness is comprehensively analysed, as well as the different bending and shear behaviours of the various sheathing materials. The results show that reducing the fastener spacing can significantly improve the stiffness of OSB wall elements, while it is less critical for FPB elements used in mid-rise timber buildings. A comparison of external and internal wall elements revealed a minimal difference in racking stiffness (3.3%) for OSB and FPB specimens, highlighting their comparable performance. The inclusion of RC sheathing on one side of the LTF elements showed significant potential to improve torsional behaviour and in-plane racking stiffness, making it a viable solution for strengthening prefabricated multi-storey timber buildings. These findings provide valuable guidance for optimizing the design of LTF walls, ensuring improved structural performance and extended application possibilities in modern timber construction.
Ključne besede: timber, structures, light timber-framed element, modelling, numerical analysis
Objavljeno v DKUM: 17.03.2025; Ogledov: 0; Prenosov: 7
.pdf Celotno besedilo (3,47 MB)
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9.
Optimizing H-BIM workflow for interventions on historical building elements
Sara Guerra de Oliveira, Salvatore Antonio Biancardo, Andrej Tibaut, 2022, izvirni znanstveni članek

Opis: Intervention projects for historical buildings depend on the quality of multidisciplinary data sets; their collection, structure, and semantics. Building information model (BIM) based workflows for historical buildings accumulate some of the data sets in a shared information model that contains the building’s geometry assemblies with associated attributes (such as material). A BIM model of any building can be a source of data for different engineering assessments, for example, solar and wind exposure and seismic vulnerability, but for historic buildings it is particularly important for interventions like conservation, rehabilitation, and improvements such as refurbishment and retrofitting. When the BIM model is abstracted to a semantic model, enabling the use of semantic technologies such as reasoning and querying, semantic links can be established to other historical contexts. The semantic technologies help historic building experts to aggregate data into meaningful form. Ontologies provide them with an accurate knowledge representation of the concepts, relationships, and rules related to the historic building. In the paper, we are proposing an improved workflow for the transformation of a heritage BIM model to a semantic model. In the BIM part the workflow demonstrates how the fully parametric modelling of historical building components is relevant, for example, in terms of reusability and adaptation to a different context. In the semantic model part, ontology reuse, reasoning, and querying mechanisms are applied to validate the usability of the proposed workflow. The presented work will improve knowledge-sharing and reuse among stakeholders involved in historic building projects.
Ključne besede: heritage building information modelling (H-BIM), algorithmic design, semantic model, ifcOWL, Erlangen CRM, OWL, SPARQL
Objavljeno v DKUM: 13.03.2025; Ogledov: 0; Prenosov: 1
.pdf Celotno besedilo (5,00 MB)
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10.
Predictive modelling of weld bead geometry in wire arc additive manufacturing
Kristijan Šket, Miran Brezočnik, Timi Karner, Rok Belšak, Mirko Ficko, Tomaž Vuherer, Janez Gotlih, 2025, izvirni znanstveni članek

Opis: This study investigates the predictive modelling of weld bead geometry in wire arc additive manufacturing (WAAM) through advanced machine learning methods. While WAAM is valued for its ability to produce large, complex metal parts with high deposition rates, precise control of the weld bead remains a critical challenge due to its influence on mechanical properties and dimensional accuracy. To address this problem, this study utilized machine learning approaches—Ridge regression, Lasso regression and Bayesian ridge regression, Random Forest and XGBoost—to predict the key weld bead characteristics, namely height, width and cross-sectional area. A Design of experiments (DOE) was used to systematically vary the welding current and travelling speed, with 3D weld bead geometries captured by laser scanning. Robust data pre-processing, including outlier detection and feature engineering, improved modelling accuracy. Among the models tested, XGBoost provided the highest prediction accuracy, emphasizing its potential for real-time control of WAAM processes. Overall, this study presents a comprehensive framework for predictive modelling and provides valuable insights for process optimization and the further development of intelligent manufacturing systems.
Ključne besede: wire arc additive manufacturing, WA AM, predictive modelling, machine learning, weld bead geometry, XGBoost
Objavljeno v DKUM: 13.03.2025; Ogledov: 0; Prenosov: 8
.pdf Celotno besedilo (3,54 MB)

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