1. Reinforcing ethyl cellulose aerogels with poly(lactic acid) for enhanced bone regenerationGabrijela Horvat, Jan Rožanc, Uroš Maver, Matjaž Finšgar, Željko Knez, Zoran Novak, 2024, original scientific article Abstract: Developing double porous biodegradable and biocompatible scafolds that can incorporate and release drugs in a controlled manner holds immense potential in regenerative medicine. This study presents a synthesis method for preparing a macro-mesoporous scafold, where poly(lactic acid) adds to the macroporous region and mechanical properties, and ethyl cellulose adds to the surface area (182 m2 /g). High surface area enables the incorporation of model drug indomethacin with an entrapment efciency of 17.0% and its later controlled release profle. The resulting scafold has desirable mechanical properties in the range of a natural trabecular bone with a compressive modulus of 22.4 MPa. The material is stable in the simulated body fuids for 120 days before the slow degradation starts. In vitro studies demonstrate the material’s ability to support bone cell adhesion, proliferation, and diferentiation, promoting osteogenic activity. Overall, the unique combination of poly(lactic acid) and ethyl cellulose produces advanced materials with tailored macro and mesopore properties, remarkable mechanical properties, optimal degradation rate, and drug delivery potential, making it a promising candidate for bone scafolds in regenerative medicine and tissue engineering Keywords: bio composite, polymer-matrix composites (PMCs), polymers, porosity/voids, secondary ion mass spectrometry Published in DKUM: 23.08.2024; Views: 130; Downloads: 6 Full text (2,87 MB) |
2. Enhancing PLS-SEM-Enabled research with ANN and IPMA : research study of enterprise resource planning (ERP) systems’ acceptance based on the technology acceptance model (TAM)Simona Sternad Zabukovšek, Samo Bobek, Uroš Zabukovšek, Zoran Kalinić, Polona Tominc, 2022, original scientific article Abstract: PLS-SEM has been used recently more and more often in studies researching critical factors influencing the acceptance and use of information systems, especially when the technology acceptance model (TAM) is implemented. TAM has proved to be the most promising model for researching different viewpoints regarding information technologies, tools/applications, and the acceptance and use of information systems by the employees who act as the end-users in companies. However, the use of advanced PLS-SEM techniques for testing the extended TAM research models for the acceptance of enterprise resource planning (ERP) systems is scarce. The present research aims to fill this gap and aims to show how PLS-SEM results can be enhanced by advanced techniques: artificial neural network analysis (ANN) and Importance–Performance Matrix Analysis (IPMA). ANN was used in this research study to overcome the limitations of PLS-SEM regarding the linear relationships in the model. IPMA was used in evaluating the importance and performance of factors/drivers in the SEM. From the methodological point of view, results show that the research approach with ANN artificial intelligence complements the results of PLS-SEM while allowing the capture of nonlinear relationships between the variables of the model and the determination of the relative importance of each factor studied. On other hand, IPMA enables the identification of factors with relatively low performance but relatively high importance in shaping dependent variables. Keywords: traditional PLS-SEM, artificial neural network (ANN) analysis, Importance–Performance Matrix Analysis (IPMA), ERP system acceptance, TAM model Published in DKUM: 09.07.2024; Views: 103; Downloads: 9 Full text (2,52 MB) This document has many files! More... |
3. Axioms of decision criteria for 3D matrix games and their applicationsMurat Özkaya, Burhaneddin İzgi, Matjaž Perc, 2022, original scientific article Abstract: In this paper, we define characteristic axioms for 3D matrix games and extend the definitions of the decision criteria under uncertainty to three dimensions in order to investigate the simultaneous effect of two different states on the decision process. We first redefine the Laplace, Wald, Hurwicz, and Savage criteria in 3D. We present a new definition depending on only the ∞-norm of the 3D payoff matrix for the Laplace criterion in 3D. Then, we demonstrate that the Laplace criterion in 3D explicitly satisfies all the proposed axioms, as well as the other three criteria. Moreover, we illustrate a fundamental example for a three-dimensional matrix with 3D figures and show the usage of each criterion in detail. In the second example, we model a decision process during the COVID-19 pandemic for South Korea to show the applicability of the 3D decision criteria using real data with two different states of nature for individuals’ actions for the quarantine. Additionally, we present an agricultural insurance problem and analyze the effects of the hailstorm and different speeds of wind on the harvest by the 3D criteria. To the best of our knowledge, this is the first study that brings 3D matrices in decision and game theories together. Keywords: game theory, decision criteria, matrix game, common goods, characteristic axioms, multi-state games, three-dimensional matrix games, game against nature, COVID-19, insurance problem Published in DKUM: 27.05.2024; Views: 229; Downloads: 12 Full text (474,80 KB) This document has many files! More... |
4. Extended matrix norm method : applications to bimatrix games and convergence resultsBurhaneddin İzgi, Murat Özkaya, Nazım Kemal Üre, Matjaž Perc, 2023, original scientific article Abstract: In this paper, we extend and apply the Matrix Norm (MN) approach to the nonzero-sum bimatrix games. We present preliminary results regarding the convergence of the MN approaches. We provide a notation for expressing nonzero-sum bimatrix games in terms of two matrix games using the idea of separation of a bimatrix game into two different matrix games. Next, we prove theorems regarding boundaries of the game value depending on only norms of the payoff matrix for each player of the nonzero-sum bimatrix game. In addition to these, we refine the boundaries of the game value for the zero/nonzero sum matrix games. Therefore, we succeed to find an improved interval for the game value, which is a crucial improvement for both nonzero and zero-sum matrix games. As a consequence, we can solve a nonzero-sum bimatrix game for each player approximately without solving any equations. Moreover, we modify the inequalities for the extrema of the strategy set for the nonzero-sum bimatrix games. Furthermore, we adapt the min-max theorem of the MN approach for the nonzero-sum bimatrix games. Finally, we consider various bimatrix game examples from the literature, including the famous battle of sexes, to demonstrate the consistency of our approaches. We also show that the repeated applications of Extended Matrix Norm (EMN) methods work well to obtain a better-estimated game value in view of the obtained convergence results. Keywords: game theory, nonzero sum game, bimatrix game, matrix norms, battle of sexes, convergence Published in DKUM: 15.04.2024; Views: 317; Downloads: 244 Full text (838,66 KB) This document has many files! More... |
5. Implementation of food matrix effects into chemical food contaminant risk assessmentAna-Andreea Cioca, Tomaž Langerholc, Livija Tušar, 2022, original scientific article Abstract: Food risk assessment plays an important role in protecting public health worldwide. Stakeholders involved in food risk assessment, such as national authorities, agencies, non-governmental organisations (NGOs), industry and consumers, need to properly understand the terminology of food risk assessment effectively. In this respect, the first part of the EU-FORA work programme (WP1) aimed to provide insights into the actual translation of two essential terms used in food risk assessment. ‘Hazard’ and ‘risk’ were first identified and compared between the English version of various food regulations and their equivalents in the national legislation of EU Member States. The comparison and critical evaluation revealed several inconsistencies. These inconsistencies could lead to misinterpretations, followed by errors in conducting risk assessments or communicating risks. We recommend that consistency is restored and maintained so that the message is properly communicated. The second part of the work programme (WP2) was focused on a specific area within chemical risk assessment (CRA). In this context, special attention was given to the impact of the food matrix on the bioaccessibility and bioavailability of heavy metals and metalloids. After collection and careful selection of data from scientific journals, a database with information on the bioaccessibility and bioavailability of cadmium (Cd), lead (Pb), mercury (Hg) and arsenic (As) in different food matrices was created for future statistical analyses related to dietary exposure. Keywords: hazard, risk, food regulation, chemical contaminants, bioavailability, bioaccessibility, food matrix Published in DKUM: 18.09.2023; Views: 476; Downloads: 20 Full text (1,96 MB) This document has many files! More... |
6. A note on star partial order preservers on the set of all variance-covariance matricesGregor Dolinar, Bojan Kuzma, Janko Marovt, Dijana Mosić, 2023, original scientific article Abstract: Let ▫$H_n^+(\mathbb{R})$▫ be the cone of all positive semidefinite ▫$n \times n$▫ real matrices. We describe the form of all surjective maps on ▫$H_n^+(\mathbb{R})$▫, ▫$n=3$▫, that preserve the star partial order in both directions. Keywords: preserver, star partial order, linear model, variance-covariance matrix Published in DKUM: 10.07.2023; Views: 581; Downloads: 19 Link to full text This document has many files! More... |
7. DIFFRACTION GRATINGS FORMED BY BENT-CORE LIQUID CRYSTALS IN THE TWIST – BEND NEMATIC PHASEMuhammad Ali, 2021, doctoral dissertation Abstract: In this thesis, we study the structure and optical transmission properties of the twist-bend nematic liquid crystalline phase, made of bent dimers, confined in thin planar cells. Confinement leads to the formation of a periodic modulated structure, the formation of which is explained as follows. The twist-bend nematic phase is characterized by a heliconical modulation of the molecular long axes. Due to a short pitch of modulation (approximately 10 nm), the twist-bend nematic phase behaves as a pseudo-layered medium. At temperatures below the nematic – twist-bend nematic phase transition, the heliconical pitch and thus the thickness of the pseudo-layers reduces, which leads to a two-dimensional undulation of pseudo-layers in the direction perpendicular to the cell surfaces and along the surfaces. The undulated structure is responsible for a stripe texture observed under a polarizing microscope and acts as a diffraction grating.
We constructed theoretical models to predict the pseudo-layer structure of a confined twist-bend nematic phase and to describe the properties of light diffracted on such cells. The free energy of the two-dimensional pseudo-layer structure of the twist-bend nematic phase is expressed in terms of the nematic director field, by which we describe the direction of the heliconical axis, and a complex smectic order parameter, the gradient of which gives the direction of the layer normal. At first, we assume that pseudo-layers are perpendicular to the surfaces (bookshelf geometry) and find a stable structure by assuming an ansatz for the pseudo-layer displacement from the bookshelf geometry and then minimizing the free energy at a very strong and very weak surface anchoring. In this way a threshold condition for the onset of the modulated structure is obtained, as well as the amplitude and period of modulation. Next, we assume that, at the onset of the twist-bend nematic phase, pseudo-layers are formed at some angle (pre-tilt) with respect to the surface. We find that in both cases, the bookshelf and pre-tilted one, the calculated period of modulation far from the phase transition is always approximately twice the cell thickness, which agrees with experimental observations.
The properties of light diffracted by the spontaneously formed grating were studied both experimentally and theoretically. We measured the intensity and polarization properties of the first two orders of the diffracted light and the temperature dependence of the polarization of the second order diffraction peaks. To predict the observed properties of the diffracted light and to simplify the description of such gratings, we consider different preliminary models of a one-dimensional spatial variation of the optic axis, the direction of which is given by two angles. A transfer matrix method is used and a good agreement between the experimental and theoretical results is obtained. In a more comprehensive approach, we determine the spatial variation of the optic axis direction from the modeled structure. The electric field in the diffracted light is obtained by using the transfer matrix method and beam propagation method. In the case of a pre-tilt of the pseudo-layers and very strong surface anchoring both methods give good qualitative agreement with experimental results, only in the case of the temperature dependence of the second order diffraction peaks, a more complex beam propagation method is superior to the transfer matrix method.
The thesis is divided into three parts. In the first part, we focus on the physical properties of the twist-bend nematic phase and its structure in thin planar cells. In the second part, a continuum model is proposed and finally, the properties of diffracted light are discussed and theoretically predicted by using the beam propagation method and transfer matrix method. Keywords: Bent-dimer liquid crystals, twist-bend nematic phase, undulation of pseudo-layers, polarization, diffraction grating, beam propagation method, transfer matrix method. Published in DKUM: 21.10.2021; Views: 1359; Downloads: 89 Full text (10,65 MB) |
8. First model-independent Dalitz analysis of $B^0 \to D^0K^{\ast 0}$, $D\to K_S^0\pi ^+\pi ^-$ decayK. Negishi, Jyoti Prakash Biswal, Marko Bračko, Boštjan Golob, Samo Korpar, Peter Križan, Tara Nanut, Rok Pestotnik, Marko Petrič, Eva Ribežl, Samo Stanič, Marko Starič, Luka Šantelj, Anže Zupanc, 2016, original scientific article Abstract: We report a measurement of the amplitude ratio $r_S$ of $B^0 \to D^0K^{\ast 0}$ and $B^0 \to \bar {D^0}K^{\ast 0}$ decays with a Dalitz analysis of $D\to K_S^0\pi ^+\pi ^-$ decays, for the first time using a model-independent method. We set an upper limit $r_S < 0.87$ at the 68% confidence level, using the full data sample of $711\,{\rm fb}^{-1}$ corresponding to $772\times 10^6$ $B\bar {B}$ pairs collected at the $\Upsilon (4S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. This result is obtained from observables $x_- = +0.4 ^{+1.0 +0.0}_{-0.6 -0.1} \pm 0.0$, $y_- = -0.6 ^{+0.8 +0.1}_{-1.0 -0.0} \pm 0.1$, $x_+ = +0.1 ^{+0.7 +0.0}_{-0.4 -0.1} \pm 0.1$, and $y_+ = +0.3 ^{+0.5 +0.0}_{-0.8 -0.1} \pm 0.1$, where $x_\pm = r_S \cos (\delta _S \pm \phi _3)$, $y_\pm = r_S \sin (\delta _S \pm \phi _3)$, and $\phi _3\ (\delta _S)$ is the weak (strong) phase difference between $B^0 \to D^0K^{\ast 0}$ and $B^0 \to \bar {D^0}K^{\ast 0}$. Keywords: CO2, CO3, Cabibbo-Kobayashi-Maskawa quark-mixing matrix, CP violation, experimental particle physics Published in DKUM: 21.07.2017; Views: 1788; Downloads: 285 Full text (555,01 KB) This document has many files! More... |
9. Simplified computation of matchings in polygraphsAnte Graovac, Damir Vukičević, Damir Ježek, Janez Žerovnik, 2005, original scientific article Abstract: Matching polynomial and perfect matchings for fasciagraphs, rotagraphs and twisted rotagraphs are treated in the paper. Classical transfer matrix approach makes it possible to get recursions for matching polynomial and perfect matchings, but the order of the matrix grows exponentially in the number of the linking edges between monographs. Novel transfer matrices are introduced whose order is much lower than that in classical transfer matrices. The virtue of the method introduced is especially pronounced when twoor more linking edges end in the same terminal vertex of a monograph. An example of a polyacene polygraph with extended pairings is given where a novel matrix has only 16 entries as compared to 65536 entries in the classical transfer matrix. However, all pairings are treated here on equal footing, but the method introduced can be applied to selected types of pairings of interest in chemistry. Keywords: polygraphs, matching polynomial, matchings, perfect matchings, Kekulé structures, extended structures, recursive enumeration, transfer matrix method Published in DKUM: 05.07.2017; Views: 1583; Downloads: 92 Full text (102,97 KB) This document has many files! More... |
10. Model of sustainable growth and development of the cableway transport system in SloveniaSergej Težak, Ratko Zelenika, Drago Sever, 2011, original scientific article Abstract: The cableway transport system is very important for the Slovenian tourist economy. Within the Slovene transport system, the cableway transport subsystem has a specific role because it allows and ensures access to regions which are difficult to access or completely inaccessible by other transport subsystems owing to the configuration of the area. The quality and development of transport services are directly linked to the introduction of new cableways. New technical achievements, which are nowadays used in cableways, all provide greater capacity and higher speed of cableways, which, however, results in their higher maintenance and exploitation costs.
The cableway transport system is being developed in Slovenia, but not on principles of sustainable development. This paper presents a model of sustainable growth and development of the cableway transport system in Slovenia based on which it is possible to determine assumptions for future growth so that the Slovene cableway transport system would approach standards of such highly developed systems. The new model includes ten essential elements of this system for which growth rates were calculated. Keywords: cableway transport system, cableways, econometrics, growth matrix, sustainbale growth, winter tourism, mountain tourist centre Published in DKUM: 05.06.2017; Views: 1542; Downloads: 412 Full text (513,45 KB) This document has many files! More... |