1. Twist grain boundary phases in proper ferroelectric liquid crystals realmDamian Pociecha, Jadwiga Szydłowska, Nataša Vaupotič, Katarzyna Kwiatkowska, Marijus Juodka, Julian Spiess, John M. D. Storey, Corrie T. Imrie, Rebecca Walker, Ewa Górecka, 2025, izvirni znanstveni članek Ključne besede: chirality, liquid crystals, proper ferroelectrics, twist-grain-boundary
Objavljeno v DKUM: 19.08.2025; Ogledov: 0; Prenosov: 9
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2. Parameter estimation for the basic Zirka-Moroz history-dependent hysteresis model for electrical steelsMartin Petrun, Ermin Rahmanović, 2025, izvirni znanstveni članek Opis: History-dependent hysteresis models can potentially describe magnetization curves of all orders accurately. This property is essential for modeling magnetization and power loss in magnetic components subjected to distorted excitation waveforms, which result in complex magnetization patterns such as offset minor loops. The basic Zirka–Moroz history-dependent hysteresis model offers a good balance between the model’s complexity and accuracy. However, estimating the model’s parameters can be challenging. This research provides insight into the parameter estimation procedure for the discussed hysteresis model. Based on the measured first-order reversal curves, the fundamental two-step parameter estimation procedure was employed and analyzed for two non-oriented and one grain-oriented electrical steel types used widely in contemporary electric drives and electromagnetic devices. For each sample evaluated, two sets of parameters were estimated and compared to the reference parameters recommended for non-oriented electrical steels. The performed analysis is essential for gaining a comprehensive understanding of the capabilities, challenges, requirements, and limitations associated with estimating the parameters and performance of the analyzed model for specific electrical steel types.
Ključne besede: history-dependent hysteresis model, grain-oriented electrical steel, magnetic hysteresis, non-oriented electrical steel, parameter estimation, static hysteresis
Objavljeno v DKUM: 30.05.2025; Ogledov: 0; Prenosov: 6
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3. Increased planting speed did not affect silage and grain yield of maize, while saving seed and energyFilip Vučajnk, Igor Šantavec, Darja Kocjan Ačko, Jurij Rakun, Jože Verbič, Rajko Bernik, Stanislav Trdan, Matej Vidrih, 2020, izvirni znanstveni članek Opis: Optimal planting speed of vacuum maize planters is usually suggested by planter’s manufacturers, while increased planting speed may influence plant spacing and finally yield. Our hypothesis was that by increasing planting speed over the suggested level plant spacing variability will also increase which will result in decrease of silage and grain yield and saving of seed and energy. The field trial consisted of three planting speeds of 7, 9 and 11 km/h in the form of random blocks. The following measurements were taken as follows: plant spacing, silage and grain yield, fuel and energy use at planting. Results in this study show that planting speed did not have significant influence on silage and grain yield of maize, while up to 10% less seed was needed per hectare and fuel and energy use was lower for 15%. By the increase of planting speed the distance between the plants in a row, and in most cases also the plant spacing variability increased. It was noticed that by increasing planting speed plant density decreased. This research established that at higher planting speeds significant increase of the silage yield per individual plant and of the grain yield per individual plant was achieved. The ear parameters also show that the kernel mass per individual ear, the ear mass, and the cob mass, as well as the individual kernel mass, are larger at the planting speed of 11 km/h than at the planting speed of 7 km/h. At the latter planting speed, significantly higher fuel consumption per hectare and higher energy use was achieved than at the other two planting speeds. Overall the main benefits of planting speed of 11 km/h is saving seed and energy at planting while maintaning the same level of silage and grain yield compared to lower planting speeds used in the trial.
Ključne besede: energy use, grain yield, maize, planting speed, plant spacing, seed savings, silage yield, vacuum planter
Objavljeno v DKUM: 11.03.2025; Ogledov: 0; Prenosov: 10
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4. Nanofiltration of the remaining whey after kefir grains’ cultivationMarjana Simonič, 2022, izvirni znanstveni članek Opis: Acid whey is derived from fresh cheese. The proteins were isolated by a monolithic ion-exchange column. The remaining whey fraction was used as a starter culture substrate of kefir grains. The aim of this work was, firstly, to study the possibility of column replacement by a UF membrane. If we succeeded, the concentrate would be used as a starter culture substrate of kefir grains. The second part of the research was to purify the remaining solution. The idea was to separate this solution to the permeate and the concentrate by nanofiltration. Further application of both filtration streams was tested as aqueous solutions or dried matter. Chemical and microbiological analyses were performed of both the permeate and the concentrate. The permeate analyses showed that lactose had been fully removed. The aqueous permeate was not stable, mainly due to an increase of total bacteria from 103 to 106 CFU/mL. Therefore, the permeate was spray-dried. The dry permeate was added to the moisture solution in different concentrations. The results showed that up to 0.5% of the dry permeate could be added to the moisturizing solution, with negligible changes in properties having the ability to inhibit acne growth. Anaerobic digestion of industrial sludge was performed with the addition of an aqueous concentrate, which showed improvement in anaerobic fermentation.
Ključne besede: kefir grain cultivation, remaining whey, nanofiltration
Objavljeno v DKUM: 05.12.2024; Ogledov: 0; Prenosov: 12
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5. Experimental advances in nanoparticle-driven stabilization of liquid-crystalline blue phases and twist-grain boundary phasesGeorge Cordoyiannis, Marta Lavrič, Vasileios Tzitzios, Maja Trček, Ioannis Lelidis, George Nounesis, Samo Kralj, Jan Thoen, Zdravko Kutnjak, 2021, pregledni znanstveni članek Opis: Recent advances in experimental studies of nanoparticle-driven stabilization of chiral liquid-crystalline phases are highlighted. The stabilization is achieved via the nanoparticles’ assembly in the defect lattices of the soft liquid-crystalline hosts. This is of significant importance for understanding the interactions of nanoparticles with topological defects and for envisioned technological applications. We demonstrate that blue phases are stabilized and twist-grain boundary phases are induced by dispersing surface-functionalized CdSSe quantum dots, spherical Au nanoparticles, as well as MoS2 nanoplatelets and reduced-graphene oxide nanosheets in chiral liquid crystals. Phase diagrams are shown based on calorimetric and optical measurements. Our findings related to the role of the nanoparticle core composition, size, shape, and surface coating on the stabilization effect are presented, followed by an overview of and comparison with other related studies in the literature. Moreover, the key points of the underlying mechanisms are summarized and prospects in the field are briefly discussed.
Ključne besede: liquid crystals, nanoparticles, quantum dots, reduced-graphene oxide, calorimetry, microscopy, blue phases, twist-grain boundary phases, disclination lines, screw dislocations
Objavljeno v DKUM: 09.08.2024; Ogledov: 97; Prenosov: 13
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6. Benchmarking plant diversity of Palaearctic grasslands and other open habitatsIdoia Biurrun, Remigiusz Pielech, Iwona Dembicz, François Gillet, Łukasz Kozub, Corrado Marcenò, Triin Reitalu, Koenraad Van Meerbeek, Riccardo Guarino, Milan Chytrý, Nataša Pipenbaher, Sonja Škornik, 2021, izvirni znanstveni članek Opis: Aims: Understanding fine-grain diversity patterns across large spatial extents is fundamental for macroecological research and biodiversity conservation. Using the GrassPlot database, we provide benchmarks of fine-grain richness values of Palaearctic open habitats for vascular plants, bryophytes, lichens and complete vegetation (i.e., the sum of the former three groups).
Location: Palaearctic biogeographic realm.
Methods: We used 126,524 plots of eight standard grain sizes from the GrassPlot database: 0.0001, 0.001, 0.01, 0.1, 1, 10, 100 and 1,000 m2 and calculated the mean richness and standard deviations, as well as maximum, minimum, median, and first and third quartiles for each combination of grain size, taxonomic group, biome, region, vegetation type and phytosociological class.
Results: Patterns of plant diversity in vegetation types and biomes differ across grain sizes and taxonomic groups. Overall, secondary (mostly semi-natural) grasslands and natural grasslands are the richest vegetation type. The open-access file ”GrassPlot Diversity Benchmarks” and the web tool “GrassPlot Diversity Explorer” are now available online (https://edgg.org/databases/GrasslandDiversityExplorer) and provide more insights into species richness patterns in the Palaearctic open habitats.
Conclusions: The GrassPlot Diversity Benchmarks provide high-quality data on species richness in open habitat types across the Palaearctic. These benchmark data can be used in vegetation ecology, macroecology, biodiversity conservation and data quality checking. While the amount of data in the underlying GrassPlot database and their spatial coverage are smaller than in other extensive vegetation-plot databases, species recordings in GrassPlot are on average more complete, making it a valuable complementary data source in macroecology.
Ključne besede: benchmark, bryophyte, fine-grain biodiversity, grassland, GrassPlot Diversity Explorer, lichen, open habitat, Palaearctic, scale dependence, species–area relationship, vascular plant, vegetation plot
Objavljeno v DKUM: 07.08.2024; Ogledov: 88; Prenosov: 12
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7. Influence of microdefect on fatigue properties in weld fine grain heat affected zone on nickel molybdenum alloy steel : doctoral disertationFidan Smaili, 2023, doktorska disertacija Opis: This research presents two possibilities to prepare and test the Fine Grain of a Heat Affected Zone, which, practically, could be considered as the weakest part of welded joints in the presence of any microdefect. It is a narrow zone located between the fusion zone and the unaffected base material; therefore, only a few methods are suitable to test its mechanical properties. The 18CrNiMo7-6 steel was used as the base material. As this steel is usually used for the production of dynamically loaded components, testing of its fatigue behaviour and fracture toughness was crucial, but also measurement of its hardness and impact toughness. To investigate the mechanical properties of a Fine-Grain Heat-Affected Zone (FG HAZ), two different methods for simulation of as-welded microstructures were used in this research: A weld thermal cycle simulator (WTCS) and austenitising in a laboratory furnace +
Ključne besede: weld joint, Fine Grain Heat Affected Zone, mechanical properties, fatigue crack growth
Objavljeno v DKUM: 06.10.2023; Ogledov: 458; Prenosov: 63
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8. Primerjava pretočnih šifrirnikov podatkov na modulu STM32f411 : diplomsko deloFilip Horvat, 2020, diplomsko delo Opis: V diplomskem delu smo se posvetili preučevanju vede kriptografije in šifrirnih algoritmov. Pogledali smo si delovanje pretočnih šifrirnikov, natančneje dveh algoritmov projekta eStream. Opisali smo delovanje algoritmov Salsa20/ChaCha20 in Grain v1. Njuno delovanje smo preverili na mikrokrmilniku STM32F411. Implementacijo algoritma Salsa20/ChaCha20 smo našli v knjižnici STM CryptoLib. Algoritma Grain v1 prej omenjena knjižnica ne vsebuje, zato smo ga implementirali sami. Na koncu smo primerjali njuni hitrosti šifriranja s tremi video datotekami različnih velikosti. Ugotovili smo, da se naša implementacija algoritem Grain v1 precej počasneje šifrira in dešifrira podatke kot Salsa20/ChaCha20.
Ključne besede: kriptografija, pretočni šifrirni algoritmi, eStream, ChaCha20, Grain v1, STM32F411, STM CryptoLib
Objavljeno v DKUM: 04.11.2020; Ogledov: 806; Prenosov: 64
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9. Determining the grain size distribution of granular soils using image analysisNihat Dipova, 2017, izvirni znanstveni članek Opis: Image-processing technology includes storing the images of objects in a computer and processing them with the computer for a specified purpose. Image analysis is the numerical expression of the images of objects by means of mimicking the functioning of the human visual system and the generation of numerical data for calculations that will be made later. Digital image analysis provides the capability for rapid measurement, which can be made in near-real time, for numerous engineering parameters of materials. Recently, image analysis has been used in geotechnical engineering practices. Grain size distribution and grain shape are the most fundamental properties used to interpret the origin and behaviour of soils. Mechanical sieving has some limitations, e.g., it does not measure the axial dimension of a particle, particle shape is not taken into consideration, and especially for elongated and flat particles a sieve analysis will not yield a reliable measure. In this study the grain size distribution of sands has been determined following image-analysis techniques, using simple apparatus, non-professional cameras and open-code software. The sample is put on a transparent plate that is illuminated with a white backlight. The digital images were acquired with a CCD DSLR camera. The segmentation of the particles is achieved by image thresholding, binary coding and particle labeling. The geometrical measurements of each particle are obtained using an automated pixel-counting technique. Local contacts or limited overlaps were overcome using a watershed split. The same sample was tested by traditional sieve analysis. An image-analysis-based grain size distribution has been compared with a sieve-analysis distribution. The results show that the grain size distribution of the image-based analysis and the sieve analysis are in good agreement.
Ključne besede: image analysis, image processing, grain size, sand
Objavljeno v DKUM: 18.06.2018; Ogledov: 1533; Prenosov: 189
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10. Probabilistic study of the phenomenon of crushed grains using the model of WeibullKheffache Toufik, Melbouci Bachir, 2012, izvirni znanstveni članek Opis: The crushing of grains in a granular medium is a very important phenomenon; it is a source of both physical and mechanical changes to these materials. A statistical study of the mechanical properties of a material was used to characterize the distribution and fracture mechanics in order to quantify the evolution of these distributions with sample sizes (grains and whole grains).
This work presents the results of an experimental study made on the crushing of individual grains of limestone and samples consisting of multiple grains subjected to a uniaxial loading in order to highlight the influence of the loading and the grain size on the rate of crushing. A statistical study using the Weibull method allowed us to model the problem and quantify the rate of breakage for the two cases.
The results obtained show that the rate of deflection depends on the grain size and the intensity of the applied load. Statistical modelling using the Weibull method gave us acceptable results in both cases.
Ključne besede: grain, sample, crushing, statistical study
Objavljeno v DKUM: 13.06.2018; Ogledov: 888; Prenosov: 87
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