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Coefficient of tangential restitution for non-spherical particles
Jana Wedel, Matjaž Hriberšek, Paul Steinmann, Jure Ravnik, 2024, izvirni znanstveni članek

Opis: In various industrial and naturally occurring multiphase flows, whether dilute or dense, particle interaction plays a crucial role. In most cases, the particles are non-spherical, which poses a computational challenge in terms of particle motion and particle interaction, i.e. both particle–particle and particle–wall collisions. In this study, we present a novel frictional particle collision model to be used in general fluid flows. The model is derived for superellipsoidal particle shapes and thus allows consideration of frictional collisions of a wide variety of particle geometries. In this context, we derive an expression for the tangential coefficient of restitution applicable to arbitrarily shaped particles. Furthermore, we present the performance of the novel model by applying it to demonstrative examples ranging from two- to multi-particle systems.
Ključne besede: non-spherical particles, particle collision, tangential restitution coefficient, superellipsoids
Objavljeno v DKUM: 26.02.2024; Ogledov: 127; Prenosov: 14
.pdf Celotno besedilo (5,64 MB)
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3.
Green Processing of Neat Poly(lactic acid) Using Carbon Dioxide under Elevated Pressure for Preparation of Advanced Materials : A Review (2012–2022)
Stoja L. Milovanović, Ivana Lukic, Gabrijela Horvat, Zoran Novak, Sulamith Frerich, Marcus Petermann, Carlos A. García-González, 2023, pregledni znanstveni članek

Opis: This review provides a concise overview of up-to-date developments in the processing of neat poly(lactic acid) (PLA), improvement in its properties, and preparation of advanced materials using a green medium (CO2 under elevated pressure). Pressurized CO2 in the dense and supercritical state is a superior alternative medium to organic solvents, as it is easily available, fully recyclable, has easily tunable properties, and can be completely removed from the final material without post-processing steps. This review summarizes the state of the art on PLA drying, impregnation, foaming, and particle generation by the employment of dense and supercritical CO2 for the development of new materials. An analysis of the effect of processing methods on the final material properties was focused on neat PLA and PLA with an addition of natural bioactive components. It was demonstrated that CO2-assisted processes enable the control of PLA properties, reduce operating times, and require less energy compared to conventional ones. The described environmentally friendly processing techniques and the versatility of PLA were employed for the preparation of foams, aerogels, scaffolds, microparticles, and nanoparticles, as well as bioactive materials. These PLA-based materials can find application in tissue engineering, drug delivery, active food packaging, compostable packaging, wastewater treatment, or thermal insulation, among others.
Ključne besede: aerogels, drying, foaming, impregnation, particle generation, PLA
Objavljeno v DKUM: 06.02.2024; Ogledov: 181; Prenosov: 8
.pdf Celotno besedilo (5,02 MB)
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4.
A study of particulate and gase-ous emissions of a damaged tubu-lar combustion chamber in a pellet stove
Zdravko Praunseis, 2021, izvirni znanstveni članek

Opis: Wood-burning boilers are a popular source of heating in Slovenia. However, there has been much debate about the potential negative health effects associated with wood smoke in recent years. Wood smoke is increasingly seen as a significant component of airborne particulate matter (PM), especially in the context of the new sort time standard for fine particles in ambient air. Most organic substances will be burnt in the boilers during good combustion conditions with sufficient oxygen supply and high temperature. This study presents the influence of damaged tubular combustion chamber on smoke fine-particle emissions at small scale pellet burners. This research aims to reduce the particulate matter emissions of small scale pellet boilers and contribute to cleaner air.
Ključne besede: particulate matter, small scale pellet boilers, combustion chamber, fine particle emission, pellet burner
Objavljeno v DKUM: 13.11.2023; Ogledov: 236; Prenosov: 7
.pdf Celotno besedilo (2,41 MB)
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5.
Measurement of two-particle correlations of hadrons in ▫$e^+ e^-$▫ collisions at Belle
Y.-C. Chen, Marko Bračko, Samo Korpar, Peter Križan, Tomaž Podobnik, Marko Starič, Luka Šantelj, 2022, izvirni znanstveni članek

Opis: The measurement of two-particle angular correlation functions in high-multiplicity e+e− collisions at √s=10.52  GeV is reported. In this study, the 89.5  fb−1 of hadronic e+e− annihilation data collected by the Belle detector at KEKB are used. Two-particle angular correlation functions are measured in the full relative azimuthal angle (Δϕ) and three units of pseudorapidity (Δη), defined by either the electron beam axis or the event-shape thrust axis, and are studied as a function of charged-particle multiplicity. The measurement in the thrust axis analysis, with mostly outgoing quark pairs determining the reference axis, is sensitive to the region of additional soft gluon emissions. No significant anisotropic collective behavior is observed with either coordinate analyses. Near-side jet correlations appear to be absent in the thrust axis analysis. The measurements are compared to predictions from various event generators and are expected to provide new constraints to the phenomenological models in the low-energy regime.
Ključne besede: Particle & resonance production, Quark & gluon jets, Quark-gluon plasma
Objavljeno v DKUM: 24.08.2023; Ogledov: 296; Prenosov: 8
.pdf Celotno besedilo (634,71 KB)
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6.
Measurement of the branching fraction and ▫$CP$▫ asymmetry for ▫$B \to \bar{D}^0 \pi$▫ decays
T. Bloomfield, Jyoti Prakash Biswal, Marko Bračko, Samo Korpar, Peter Križan, Rok Pestotnik, Tomaž Podobnik, Marko Starič, Luka Šantelj, 2022, izvirni znanstveni članek

Opis: We measure the branching fractions and CP asymmetries for the decays B⁰ → D¯ 0π⁰ and B⁺ → D¯ 0π⁺, using a data sample of 772 × 10⁶ BB¯ pairs collected at the ϒ(4S) resonance with the Belle detector at the KEKB e⁺e− collider. The branching fractions obtained and direct CP asym-metries are B(B⁰ → D¯ 0π⁰)=[2.70 0.06(stat) 0.10(syst)]×10−⁴, B(B⁺ → D¯ 0π⁺)=[4.53 0.02(stat) 0.15(syst)]×10−³, ACP(B⁰ → D¯ 0π⁰)= [+0.42 2.05(stat) 1.22(syst)]%, and ACP(B⁺ → D¯ 0π⁺) = [+0.19 0.36(stat) 0.57(syst)]%. The measurements of B are the most precise to date and are in good agreement with previous results, as is the measurement of ACP(B⁺ → D¯ 0π⁺). The measurement of ACP for B⁰ → D¯ 0π⁰ is the first for this mode, and the value is consistent with Standard Model expectations.
Ključne besede: branching fraction, hadronic decays, particle decays, mesons, CP violation, precision measurements
Objavljeno v DKUM: 17.08.2023; Ogledov: 256; Prenosov: 21
.pdf Celotno besedilo (506,19 KB)
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7.
Indoor positioning system based on bluetooth low energy technology and a nature-inspired optimization algorithm
Primož Bencak, Darko Hercog, Tone Lerher, 2022, izvirni znanstveni članek

Opis: Warehousing is one of the most important activities in the supply chain, enabling competitive advantage. Effective management of warehousing processes is, therefore, crucial for achieving minimal costs, maximum efficiency, and overall customer satisfaction. Warehouse Management Systems (WMS) are the first steps towards organizing these processes; however, due to the human factor involved, information on products, vehicles and workers may be missing, corrupt, or misleading. In this paper, a cost-effective Indoor Positioning System (IPS) based on Bluetooth Low Energy (BLE) technology is presented for use in Intralogistics that works automatically, and therefore minimizes the possibility of acquiring incorrect data. The proposed IPS solution is intended to be used for supervising order-picker movements, movement of packages between workstations, and tracking other mobile devices in a manually operated warehouse. Only data that are accurate, reliable and represent the actual state of the system, are useful for detailed material flow analysis and optimization in Intralogistics. Using the developed solution, IPS technology is leveraged to enhance the manually operated warehouse operational efficiency in Intralogistics. Due to the hardware independence, the developed software solution can be used with virtually any BLE supported beacons and receivers. The results of IPS testing in laboratory/office settings show that up to 98% of passings are detected successfully with time delays between approach and detection of less than 0.5 s.
Ključne besede: warehousing, indoor positioning systems, bluetooth low energy, particle swarm optimization, nature–inspired algorithm, intralogistics
Objavljeno v DKUM: 17.08.2023; Ogledov: 326; Prenosov: 29
.pdf Celotno besedilo (2,42 MB)
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8.
Empirical modeling of liquefied nitrogen cooling impact during machining Inconel 718
Matija Hriberšek, Lucijano Berus, Franci Pušavec, Simon Klančnik, 2020, izvirni znanstveni članek

Opis: This paper explains liquefied nitrogen’s cooling ability on a nickel super alloy called Inconel 718. A set of experiments was performed where the Inconel 718 plate was cooled by a moving liquefied nitrogen nozzle with changing the input parameters. Based on the experimental data, the empirical model was designed by an adaptive neuro-fuzzy inference system (ANFIS) and optimized with the particle swarm optimization algorithm (PSO), with the aim to predict the cooling rate (temperature) of the used media. The research has shown that the velocity of the nozzle has a significant impact on its cooling ability, among other factors such as depth and distance. Conducted experimental results were used as a learning set for the ANFIS model’s construction and validated via k-fold cross-validation. Optimization of the ANFIS’s external input parameters was also performed with the particle swarm optimization algorithm. The best results achieved by the optimized ANFIS structure had test root mean squared error (test RMSE) = 0.2620, and test R$^2$ = 0.8585, proving the high modeling ability of the proposed method. The completed research contributes to knowledge of the field of defining liquefied nitrogen’s cooling ability, which has an impact on the surface characteristics of the machined parts.
Ključne besede: cryogenic machining, cooling impact, Inconel 718, machine learning, adaptive neuro-fuzzy inference system, particle swarm optimization
Objavljeno v DKUM: 14.07.2023; Ogledov: 358; Prenosov: 14
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10.
Effect of particle roundness and morphology on the shear failure mechanism of granular soil under strip footing
Babak Karimi Ghalehjough, Suat Akbulut, Semet Çelik, 2018, izvirni znanstveni članek

Opis: This study investigates the effect of particles roundness and morphology on the shear failure mechanism of soil. A strip footing was modeled under laboratory conditions. Calcareous soil was tested with three roundness classes: angular, rounded and well-rounded shapes with sizes of 0.30 mm to 4.75 mm. These were divided into six different groups at three relative densities of 30%, 50% and 70%. A series of photographs was taken during the tests and analyzed using the particle image velocimetry (PIV) method to understand the soil-deformation mechanism. The results showed that increasing the sample sizes increased the affected area of the soil. At the same time, increasing the relative density caused a punching failure mechanism that went towards the general failure. The shear failure mechanism of the soil changed from general toward punching shear failure with increasing particle roundness. This effect was larger with the smaller materials. Underneath the affected layers of soil, the angular samples were deeper than the rounded and well-rounded samples. The affected depth in the angular soil was approximately 1.5B in the smallest size group. This was more than 3B and near 4B in the largest size group. Both the sides and the underlying soil layers should be considered on angular soils. The area under the footing becomes more important than the side parts after increasing the roundness of the particles.
Ključne besede: particle roundness, morphology of particles, shear failure mechanism, strip footing, PIV method, ultimate bearing capacity
Objavljeno v DKUM: 11.10.2018; Ogledov: 1494; Prenosov: 487
.pdf Celotno besedilo (701,47 KB)
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