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A conceptual model for a circular city : a case study of Maribor, Slovenia
Kristijan Brglez, Matjaž Perc, Rebeka Kovačič Lukman, 2024, original scientific article

Abstract: Cities play a crucial role in achieving sustainable development. Decision-makers require assistance in developing city transformation plans amidst the emergence of various city models. A content analysis using concept mapping was conducted to examine smart, circular, and green city models. The analysis, supported by Leximancer, revealed that city models are evolving by adopting benefcial solutions from competitors, refecting a strong focus on sustainable development. Additionally, twentyfour research areas essential for implementing a circular city were identifed and validated. Furthermore, a conceptual model for a circular city was developed, incorporating the Defne-Measure-Analyse-Improve-Control tool and a problem-solving system. Testing the model on Maribor highlighted challenges in monitoring the transition towards circularity. The study validates the established model but emphasises the need for further research and case studies to verify its practicality. This scientifc research enhances the understanding of city models and their evolution towards sustainability, providing valuable insights for decision-makers and urban planners.
Keywords: city models, conceptual model, content analysis, problem-solving structure
Published in DKUM: 29.03.2024; Views: 269; Downloads: 346
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Graph theory approaches to maturity models : master thesis
Špela Kajzer, 2024, master's thesis

Abstract: The masters thesis, which follows the paper Graph drawing applications in combinatorial theory of maturity models, in preparation, coauthored by the author of the thesis, introduces the tiled graphs as models of learning and maturing processes. In the thesis, we show how tiled graphs can combine graphs of learning spaces or antimatroids (partial cubes) and maturity models (total orders) to yield models of learning processes. We visualise processes with optimal drawings. In the thesis, we show NP-hardness of visualisation problems resulting from most detailed models. Further, we introduce a simpler model, which ignores the details of learning and for which the visualisation problem can be solved in a polynomial time. For the rest of the thesis, we consider this model. We describe an algorithm, which finds a drawing of an ordinal panel data graph with a minimal number of edge crossings. For this problem we further define an extremal crossing number for a chosen family of ordinal panel data. Further, we explore a certain type of random instances of ordinal panel data and the expected value of a crossing number for this type of random instances. After that, we define a problem of finding the most suitable ordering on categories in panel data, in other words finding the best maturity model to fit the data. We prove the NP-hardness of the problem and formulate an integer linear program. Master thesis consists of nine chapters. The first chapter contains known results and definitions from set and graph theory and a section of computational complexity theory (NP-hardness), which will be used throughout the thesis. The following chapters present the new theory introduced in the aforementioned paper in preparation and the needed additional results and definitions. In the last chapter we present the thesis and some selected parts of the thesis with the help of learning space theory. The chapter serves as both the overview of the thesis and the use case for the theory of learning spaces, presented in the thesis.
Keywords: Maturity models, learning spaces, crossing number, crossing minimisation, tile crossing number.
Published in DKUM: 14.03.2024; Views: 262; Downloads: 7
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6th International Conference on Technologies & Business Models for Circular Economy : conference proceedings
2024, proceedings

Abstract: The 6th International Conference on Technologies & Business Models for Circular Economy (TBMCE) was organized by the Faculty of Chemistry and Chemical Engineering of the University of Maribor in cooperation with Strategic Research and Innovation Partnership – Networks for the transition into circular economy (SRIP – Circular economy), managed by the Chamber of Commerce and Industry of the Štajerska. The conference was held in Portorož, Slovenia, at the Grand Hotel Bernardin from September 6th to September 8th, 2023. TBMCE 2023 was devoted to presentations of circular economy concepts, technologies and methodologies that contribute to the shift of business entities and society as a whole to a more responsible, circular management of resources. The conference program included a round table Standardization for circular economy – more secure and less complicated closing of material loops, 6 panel discussions, 1 plenary and 3 keynote lectures, oral and poster presentations. The event was under the patronage of Ministry of the Economy, Tourism and Sport and Ministry of Cohesion and Regional Development. The Netherlands joined us as a partner country.
Keywords: sircular economy, sustainable development, processes and technologies, circular business models, research and development
Published in DKUM: 26.02.2024; Views: 493; Downloads: 557
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Development of mathematical models in explicit form for design and analysis of axial flux permanent magnet synchronous machines
Franjo Pranjić, Peter Virtič, 2020, original scientific article

Abstract: This article proposes a methodology for the design of double-sided coreless axial flux permanent magnet synchronous machines, which is based on a developed model for calculating the axial component of the magnetic flux density in the middle of the distance between opposite permanent magnets, which also represents the middle of the stator. Values for different geometric parameters represent the input data for the mathematical model in explicit form. The input data are calculated by using a simplified finite element method (FEM), which means that calculations of simplified 3D models are performed. The simplified model consists of two rotor disks with surfacemounted permanent magnets and air between them, instead of stator windings. Such a simplification is possible due to similar values of permeability of the air and copper. For each simplified model of the machine the axial component of the magnetic flux density is analyzed along a line passing through the center of opposite permanent magnets and both rotor disks. Values at the middle of the distance between the opposite permanent magnets are the lowest and are therefore selected for the input data at different stator, rotor disks and permanent magnets (PM) thicknesses. Such input data enable the model to consider the nonlinearity of materials.
Keywords: axial flux, analysis, coreless, development, design, explicit form, finite element method, mathematical models, permanent magnet, synchronous
Published in DKUM: 01.12.2023; Views: 380; Downloads: 14
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Comparative analysis of synchronous motors
Vasilija Sarac, Goce Stefanov, Dragan Minovski, 2021, original scientific article

Abstract: This paper compares the parameters, steady-state and transient characteristics of two different types of synchronous motors (SM) – a motor with surface mounted magnets on the rotor, and a motor with embedded magnets and squirrel cage winding, widely known as a line-start synchronous motor. The comparison is based on results obtained from analytical, numerical and transient models of both motors for the same output power of the motors. The models for obtaining transient characteristics allow comparison of acceleration of both motors taking into consideration that the line-start SM is a self-starting motor while the SM with surface magnets is always started with the aid of a PWM inverter. The results obtained from the analytical, numerical and transient models of the motors should assist in choosing the most cost-effective solution in terms of the type of the motor for the appropriate application.
Keywords: FEM models, synchronous motors, steady-state characteristics, transient characteristics
Published in DKUM: 13.11.2023; Views: 323; Downloads: 3
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String Universality and Non-Simply-Connected Gauge Groups in 8D
Mirjam Cvetič, Markus Dierigl, Ling Lin, Hao Y. Zhang, 2020, original scientific article

Abstract: We present a consistency condition for 8D N 1 supergravity theories with nontrivial global structure G=Z for the non-Abelian gauge group, based on an anomaly involving the Z 1-form center symmetry. The interplay with other swampland criteria identifies the majority of 8D theories with gauge group G=Z, which have no string theory realization, as inconsistent quantum theories when coupled to gravity. While this condition is equivalent to geometric properties of elliptic K3 surfaces in F-theory compactifications, it constrains the unexplored landscape of gauge groups in other 8D string models.
Keywords: supergravity theories, string theory, 8D string models
Published in DKUM: 16.10.2023; Views: 444; Downloads: 15
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Conformal symmetries for extremal black holes with general asymptotic scalars in STU supergravity
Mirjam Cvetič, Christopher N. Pope, Aritra Saha, 2021, original scientific article

Abstract: We present a construction of the most general BPS black holes of STU supergravity (N = 2 supersymmetric D = 4 supergravity coupled to three vector supermultiplets) with arbitrary asymptotic values of the scalar fields. These solutions are obtained by acting with a subset of the global symmetry generators on STU BPS black holes with zero values of the asymptotic scalars, both in the U-duality and the heterotic frame. The solutions are parameterized by fourteen parameters: four electric and four magnetic charges, and the asymptotic values of the six scalar fields. We also present BPS black hole solutions of a consistently truncated STU supergravity, which are parameterized by two electric and two magnetic charges and two scalar fields. These latter solutions are significantly simplified, and are very suitable for further explicit studies. We also explore a conformal inversion symmetry of the Couch-Torrence type, which maps any member of the fourteen-parameter family of BPS black holes to another member of the family. Furthermore, these solutions are expected to be valuable in the studies of various swampland conjectures in the moduli space of string compactifications.
Keywords: black holes, extended supersymmetry, supergravity models, string theory
Published in DKUM: 16.10.2023; Views: 234; Downloads: 12
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Statistics of limit root bundles relevant for exact matter spectra of F-theory MSSMs
Martin Bies, Mirjam Cvetič, Mingqiang Liu, 2021, original scientific article

Abstract: In the largest, currently known, class of one quadrillion globally consistent F-theory Standard Models with gauge coupling unification and no chiral exotics, the vectorlike spectra are counted by cohomologies of root bundles. In this work, we apply a previously proposed method to identify toric base threefolds, which are promising to establish F-theory Standard Models with exactly three quark doublets and no vectorlike exotics in this representation. The base spaces in question are obtained from triangulations of 708 polytopes. By studying root bundles on the quark-doublet curve Cð3;2Þ1=6 and employing well-known results about desingularizations of toric K3 surfaces, we derive a triangulation independent lower bound Nˇ ð3Þ P for the number Nð3Þ P of root bundles on Cð3;2Þ1=6 with exactly three sections. The ratio Nˇ ð3Þ P =NP, where NP is the total number of roots on Cð3;2Þ1=6 , is largest for base spaces associated with triangulations of the eighth three-dimensional polytope Δ∘ 8 in the Kreuzer-Skarke list. For each of these Oð1015Þ threefolds, we expect that many root bundles on Cð3;2Þ1=6 are induced from F-theory gauge potentials and that at least every 3000th root on Cð3;2Þ1=6 has exactly three global sections and thus no exotic vectorlike quark-doublet modes.
Keywords: astrophysics, compactification, string theory models, geometry, higher-dimensional field theories, mathematical physics, quantum fields in curved spacetime, string phenomenology, supersymmetric models, topology
Published in DKUM: 16.10.2023; Views: 209; Downloads: 11
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Artificial intelligence based prediction models for individuals at risk of multiple diabetic complications : a systematic review of the literature
Lucija Gosak, Kristina Martinović, Mateja Lorber, Gregor Štiglic, 2022, review article

Abstract: Aim The aim of this review is to examine the effectiveness of artificial intelligence in predicting multimorbid diabetes-related complications. Background In diabetic patients, several complications are often present, which have a significant impact on the quality of life; therefore, it is crucial to predict the level of risk for diabetes and its complications. Evaluation International databases PubMed, CINAHL, MEDLINE and Scopus were searched using the terms artificial intelligence, diabetes mellitus and prediction of complications to identify studies on the effectiveness of artificial intelligence for predicting multimorbid diabetes-related complications. The results were organized by outcomes to allow more efficient comparison. Key issues Based on the inclusion/exclusion criteria, 11 articles were included in the final analysis. The most frequently predicted complications were diabetic neuropathy (n = 7). Authors included from two to a maximum of 14 complications. The most commonly used prediction models were penalized regression, random forest and Naïve Bayes model neural network. Conclusion The use of artificial intelligence can predict the risks of diabetes complications with greater precision based on available multidimensional datasets and provides an important tool for nurses working in preventive health care. Implications for Nursing Management Using artificial intelligence contributes to a better quality of care, better autonomy of patients in diabetes management and reduction of complications, costs of medical care and mortality.
Keywords: artificial intelligence, prediction models, diabetes, prediction of diabetes complications
Published in DKUM: 03.10.2023; Views: 263; Downloads: 43
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