1. Mathematical model-based optimization of trace metal dosage in anaerobic batch bioreactorsTina Kegl, Balasubramanian Paramasivan, Bikash Chandra Maharaj, 2025, original scientific article Abstract: Anaerobic digestion (AD) is a promising and yet a complex waste-to-energy technology. To optimize such a process, precise modeling is essential. Developing complex, mechanistically inspired AD models can result in an overwhelming number of parameters that require calibration. This study presents a novel approach that considers the role of trace metals (Ca, K, Mg, Na, Co, Cr, Cu, Fe, Ni, Pb, and Zn) in the modeling, numerical simulation, and optimization of the AD process in a batch bioreactor. In this context, BioModel is enhanced by incorporating the influence of metal activities on chemical, biochemical, and physicochemical processes. Trace metal-related parameters are also included in the calibration of all model parameters. The model’s reliability is rigorously validated by comparing simulation results with experimental data. The study reveals that perturbations of 5% in model parameter values significantly increase the discrepancy between simulated and experimental results up to threefold. Additionally, the study highlights how precise optimization of metal additives can enhance both the quantity and quality of biogas production. The optimal concentrations of trace metals increased biogas and CH4 production by 5.4% and 13.5%, respectively, while H2, H2S, and NH3 decreased by 28.2%, 43.6%, and 42.5%, respectively. Keywords: anaerobic digestion, batch bioreactor, methane production, model parameters calibration, active set optimization method, perturbation of model parameter, gradient based optimization, trace metals Published in DKUM: 30.01.2025; Views: 0; Downloads: 2
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5. Modeling and multi-objective optimization of forward osmosis processTina Kegl, Jasmina Korenak, Hermina Bukšek, Irena Petrinić, 2024, original scientific article Abstract: In order to ensure efficient wastewater treatment and seawater desalination, adequate modeling and optimization of the forward osmosis (FO) process has the potential to be very helpful. This paper deals with the FO model parameters calibration and FO process optimization by a gradient-based optimization method. For this purpose, an upgraded FO model, which involves temperature- and agent-dependent parameters, was developed. The FO model calibration was done using NaCl as agents in draw solution, while MgCl2 was used for model validation. The agreements between simulated and measured FO performance were satisfactory; relative index of agreement are higher than 0.99. By using the proposed FO model, the optimization of FO process conditions was performed with various definitions of the objective and constraint functions. In case of maximizing the water flux, minimizing reverse solute flux, and fulfilling the required constraints, the ratio of water flux and reverse solute flux increased up to 40 % for NaCl and up to 20 % for MgCl2; meanwhile the effective osmotic pressure difference was improved 2-times for NaCl and up to 3.8-times for MgCl2. The optimization process proved to be stable and efficient and can easily be adapted or upgraded for more complex dynamic FO modeling. Keywords: forward osmosis, modeling, model and process parameters, calibration procedure, gadient-based optimization Published in DKUM: 23.08.2024; Views: 67; Downloads: 18
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6. Cold agglutinins and cryoglobulins associate with clinical and laboratory parameters of cold urticariaMojca Bizjak, Mitja Košnik, Dorothea Terhorst, Dejan Dinevski, Marcus Maurer, 2021, original scientific article Abstract: Mast cell-activating signals in cold urticaria are not yet well defined and are likely to be heterogeneous. Cold agglutinins and cryoglobulins have been described as factors possibly associated with cold urticaria, but their relevance has not been explained. We performed a single-center prospective cohort study of 35 cold urticaria patients. Cold agglutinin and cryoglobulin test results, demographics, detailed history data, cold stimulation test results, complete blood count values, C-reactive protein, total immunoglobulin E levels, and basal serum tryptase levels were analyzed. Forty six percent (n = 16) of 35 tested patients had a positive cold agglutinin test and 27% (n = 9) of 33 tested patients had a positive cryoglobulin test. Cold agglutinin positive patients, when compared to cold agglutinin negative ones, were mainly female (P = 0.030). No gender-association was found for cryoglobulins. A positive cold agglutinin test, but not a positive cryoglobulin test, was associated with a higher rate of reactions triggered by cold ambient air (P = 0.009) or immersion in cold water (P = 0.041), and aggravated by increased summer humidity (P = 0.007). Additionally, patients with a positive cold agglutinin test had a higher frequency of angioedema triggered by ingestion of cold foods or drinks (P = 0.043), and lower disease control based on Urticaria Control Test (P = 0.023). Cold agglutinin levels correlated with erythrocyte counts (r = -0.372, P = 0.028) and monocyte counts (r = -0.425, P = 0.011). Cryoglobulin concentrations correlated with basal serum tryptase levels (r = 0.733, P = 0.025) and cold urticaria duration (r = 0.683, P = 0.042). Results of our study suggest that cold agglutinins and cryoglobulins, in a subpopulation of cold urticaria patients, are linked to the course and possibly the pathogenesis of their disease. Keywords: cold-induced urticaria, cold urticaria, cryoglobulins, cold agglutinin, degranulation, clinical parameters, laboratory parameters, mast cells, cold triggers Published in DKUM: 07.08.2024; Views: 104; Downloads: 8
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7. Development of an experimental Dead-End microfiltration layout and process repeatability analysisGorazd Bombek, Luka Kevorkijan, Grega Hrovat, Drago Kuzman, Aleks Kapun, Jure Ravnik, Matjaž Hriberšek, Aleš Hribernik, 2024, original scientific article Abstract: Microfiltration is an important process in the pharmaceutical industry. Filter selection and validation is a time-consuming and expensive process. Quality by design approach is important for product safety. The article covers the instrumentalization and process control of a laboratory-scale dead-end microfiltration layout. The layout is a downscale model of the actual production line, and the goal is filter validation and analysis of process parameters, which may influence filter operation. Filter size, fluid pressure, valve plunger speed, and timing issues were considered. The focus is on the identification of the most influential process parameters and their influence on the repeatability of pressure oscillations caused by valve opening. The goal was to find the worst-case scenario regarding pressure oscillations and, consequently, filter energy intake. The layout was designed as compact as possible to reduce pressure losses between the filter and valve. Valve-induced pressure oscillations proved to be prevailing over the water hammer effect. Several filters in sizes between 3.5 cm2 and 6900 cm2 were tested, and some recommendations were suggested for the reduction of energy intake of the filter and to improve the repeatability of the process. Keywords: filtration, pressure oscillations, repeatability, processes, parameters Published in DKUM: 01.02.2024; Views: 425; Downloads: 34
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8. The external bias-dependent electric field at hole-injecting electrode/[alpha]-NPD junction and its relationship to Gaussian disordered interface statesBruno Cvikl, 2019, original scientific article Abstract: An alternative interpretation of two different sets of published temperature-dependent current-voltage a-NPD (i.e. N,N'-Di(1-naphthyl)-N,N'-diphenyl-(1,11-biphenyl)-4,4'-diamine) organic semiconductor data is presented. The measurements are described in terms of the hole drift current density expressed with two parameters: the electric field at the hole-injecting interface, Eint, and, ?max, the hole mobility determined by the measured current density at the maximum value of the externally applied electric field, Ea, in a given experiment. The former parameter, depending on the contact résistance, may be a function of Ea but the latter is Ea independent, The fixed value of Eint signifies the occurrence of the space charge limited current, SCLC, within the electrode/a-NPD structures and the contact is ohmic. Then, the calculated weak bias-dependent hole drift mobility, a function of Eint, equals the well%known exponential bias-dependent mobility, and saturates. The data not displaying SCLC characteristics are used for the calculation of Eint dependence on the applied field, Ea. It is shown that the quasi-ohmic contacts cause Eint to become a strong double-valued function of the externally applied electric field, Ea, described in terms of the distorted, inverted, high order parabola. The corresponding bias-dependent hole drift mobility is non-exponential and evolves on a considerably lower level than in SCLC cases. It is found that a sufficiently increased Ea alters the quasi-ohmic contact/a-NPD region into the ohmic one. A simple model of a thin, net hole charged, electrode/a-NPD interface enables the relationship between the deduced interfacial electric field, Eint, and the Ea dependent Gaussian width, as well as the energy shift of its peak along the negative binding energy is to be investigated. The currentvoltage method appears to be a helpful expedient for the investigation of the electric field at hole-injecting electrode/organic interfaces. Keywords: electrode/organic electric field, contact affected hole mobility, organic interface disorder parameters Published in DKUM: 22.12.2023; Views: 572; Downloads: 7
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9. Audio-visual effects of a collaborative robot on worker efficiencyAljaž Javernik, Klemen Kovič, Iztok Palčič, Robert Ojsteršek, 2023, original scientific article Abstract: Collaborative workplaces are increasingly used in production systems. The possibility of
direct collaboration between robots and humans brings many advantages, as it allows the simultaneous use of human and robotic strengths. However, collaboration between a collaborative robot
and a human raises concerns about the safety of the interaction, the impact of the robot on human
health, human efficiency, etc. Additionally, research is unexplored in the field of the collaborative
robot’s audio-visual effects on the worker’s efficiency. Our study results contribute to the field of
studying collaborative robots’ audio-visual effects on the worker’s behavior. In this research, we
analyze the effect of the changing motion parameters of the collaborative robot (speed and acceleration) on the efficiency of the worker and, consequently, on the production process. Based on the
experimental results, we were able to confirm the impact of robot speed and acceleration on the
worker’s efficiency in terms of assembly time. We also concluded that the sound level and presence of
a visual barrier between the worker and robot by themselves have no effect on the worker’s efficiency.
The experimental part of the paper clearly identifies the impact of visualization on work efficiency.
According to the results, the robot’s audio-visual effects play a key role in achieving high efficiency
and, consequently, justifying the implementation of a collaborative workplace. Keywords: collaborative robot, worker efficiency, motion parameters, visual contact, sound, human-robot symmetry, repeated measures ANOVA Published in DKUM: 11.12.2023; Views: 332; Downloads: 29
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10. (Magnetic) cross-linked enzyme aggregates of cellulase from T. Reesei: a stable and efficient biocatalystDušica Ifko, Katja Vasić, Željko Knez, Maja Leitgeb, 2023, original scientific article Keywords: immobilized catalysts, biocatalysis, enzymes, cellulase activity, CLEAs, mCLEAs, optimization, characterization, parameters Published in DKUM: 06.12.2023; Views: 501; Downloads: 167
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