Iskanje po katalogu digitalne knjižnice

Opis: 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.
Ključne besede: forward osmosis, modeling, model and process parameters, calibration procedure, gadient-based optimization
Objavljeno v DKUM: 23.08.2024; Ogledov: 67; Prenosov: 9
Celotno besedilo (12,72 MB)

Opis: 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.
Ključne besede: filtration, pressure oscillations, repeatability, processes, parameters
Objavljeno v DKUM: 01.02.2024; Ogledov: 425; Prenosov: 25
Celotno besedilo (5,64 MB)
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Opis: 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.
Ključne besede: collaborative robot, worker efficiency, motion parameters, visual contact, sound, human-robot symmetry, repeated measures ANOVA
Objavljeno v DKUM: 11.12.2023; Ogledov: 332; Prenosov: 29
Celotno besedilo (2,86 MB)
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Opis: Two different electrical circuits were analysed in this paper. The first was an RC circuit consisting of a resistor R, a capacitor C, and a DC voltage u, while the second was an RLC circuit consisting of a resistor R, a capacitor C, a DC voltage u and an inductor L. Both circuits were described using the state space mathematical model and, on this basis, graphs for charging and discharging a capacitor were plotted. Both circuits were described using differential equations for electrical current through a capacitor and voltage over a capacitor. Finally, different values of the R (resistance), L (inductance) and C (capacitance) parameters were taken, and graphs were plotted for voltage over capacitor. The purpose of the study was to explore how different values of parameters influence capacitor charging and discharging.
Ključne besede: RC circuit, RLC circuit, state space, transfer function, differential equations, parameters R, L, C, damping
Objavljeno v DKUM: 30.10.2023; Ogledov: 278; Prenosov: 11
Celotno besedilo (1,20 MB)
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Opis: Technological parameters included in energy density (ED) are the more powerful tools in selective laser melting (SLM) technology which can be used in the time of fabrication to regulate chemical, metallurgical, and mechanical properties of a product. The volumetric Energy Density (ED) depends on the energy input employed by the laser power, scanning speed, hatch spacing, and the layer thickness. Density, microstructure, surface morphology, dimension accuracy, strength and porosity including the number of pores, place of the pore, size of a pore shape of a pore, inclusions of pores of an SLM product depends on the processing parameters. As the powder material fusion process is done by track by track and layer by layer, the architecture of the microstructure in a product is oriented as the direction of building up too. The research has emphasized on metallurgical properties, tensile properties, and producing the non-porous products from Ti-6Al-4V alloy powder and surface modification using bioactive polymer for orthopedic application. The research has followed four steps to study the metallurgical properties and finding out the combinations of technological parameters in producing non-porous products. The purpose of the first step of the study was to examine the effects of ED on the product properties and to obtain an optimum ED as well as the optimal range of scanning speed. The second step of the study has focused on the influences of laser power. The third step of the study has investigated the effect of amounts of track overlapping and hatch spacing. Almost a zero-porosity product has been able to produce by following these three steps of the ongoing research. The fourth step has studied the metallurgical properties emphasizing on re-melting of every layer. High-density products have been found in the fourth step where a small amount of very small sized pores are present as a result of keyhole effect and gaseous bubble entrapment mainly. Four buildup orientations have been selected for each ED in the first step of the study to examine the tensile properties of the products. The best buildup orientation has been seen in longitudinally vertical tensile specimens considering tensile properties. The tensile properties have also been studied in the second and third step of the study with best build up orientation of the tensile specimens. The alterations of metallurgical and tensile properties have also been investigated after heat-treatment of the specific samples. Dimensional accuracies were also invigilated on the cubic, and tensile specimens over the studies and consequently, inaccuracies have been noticed. The fifth step of the study has observed the pore properties, adhesion properties, the compressive strength of gelatin coating manufactured using unidirectional freezing and the freeze-drying process of three different gelatin concentrations on four different surfaced Ti-6Al-4V alloy substrates. The results indicate that the coating properties depend on the substrate’s surface texture as well as the concentration of gelatin. Above 80% of porosity, interconnected and well-aligned pores of 75-200 μm have been obtained which is required to stimulate bone ingrowth histologically.
Ključne besede: selective laser melting, unidirectional freezing, fabricating parameters, porosity, microstructure, mechanical strength
Objavljeno v DKUM: 01.04.2019; Ogledov: 1896; Prenosov: 146
Celotno besedilo (10,52 MB)