| | SLO | ENG | Piškotki in zasebnost

Večja pisava | Manjša pisava

Iskanje po katalogu digitalne knjižnice Pomoč

Iskalni niz: išči po
išči po
išči po
išči po
* po starem in bolonjskem študiju


1 - 10 / 177
Na začetekNa prejšnjo stran12345678910Na naslednjo stranNa konec
Fluorescence based dopamine detection
Valeriia V. Sliesarenko, Urban Bren, Aleksandra Lobnik, 2024, izvirni znanstveni članek

Opis: Dopamine is an important hormone and neurotransmitter, and its levels in human fluids can indicate stress, depression, and various mental disorders. Food products, as well as medications, affect its level in the human body greatly. Therefore, dopamine monitoring is crucial, and necessary for improving the quality of life. The priority is to search for simple and environmentally friendly sensor systems for the in vitro detection of dopamine, enabling mass utilization. In this study, we explored the use of o-phthalaldehyde (OPA) as an indicator for the detection of dopamine, with fluorescence in the visible range (λex/λem = 390/455 nm), while direct dopamine fluorescence measurement was in the UV range (λex/λem = 280/320 nm). The longer excitation/emission wavelengths of dopamine-OPA complex, as well as lower detection limits, are useful for developing a simple detection method using LEDs. Three types of poloxamers were tested as additives to improve the fluorescence signal from the reaction between dopamine and OPA. Pluronic F127 led to a 16-fold increase in the fluorescence. Utilizing 4% Pluronic F127 with OPA at pH 7 resulted in a linear response within concentration ranges of dopamine (0.5–3 µM), achieving a limit of detection of 0.015 µM. In contrast, a direct detection of dopamine within the same range exhibited a detection limit of 0.13 µM.
Ključne besede: fluorometric method, dopamine, O-phthalaldehyde, Pluronic F127
Objavljeno v DKUM: 28.05.2024; Ogledov: 10; Prenosov: 2
.pdf Celotno besedilo (3,51 MB)
Gradivo ima več datotek! Več...

Design and optimization of a spherical magnetorheological actuator
Jakob Vizjak, Anton Hamler, Marko Jesenik, 2023, izvirni znanstveni članek

Opis: Recently, an increasing number of electromagnetic devices have been using smart fluids. These include ferrofluids, electrorheological fluids, and magnetorheological (MR) fluids. In the paper, magnetorheological fluids are considered for use in a spherical actuator for haptic applications. An approach is presented to the design and optimization of such a device, using finite element method modelling linked with differential evolution (DE). Much consideration was given to the construction of the objective function to be minimized. A novel approach to objective function assembly was used, using reference values based on the model design and created with parameters set to the midpoint values of the selected range. It was found to be a useful strategy when the reference values are unknown. There were four parameters to be optimized. Three of them gravitated towards the boundary value, and the fourth (actuator radius) was somewhere in between. The value of the objective function reached a minimum in the range of actuator radius between 42.9880 mm and 45.0831 mm, which is about a 5% difference in regard to the actuator radius. Three passes of optimization were performed with similar results, proving the robustness of the algorithm.
Ključne besede: magnetorheological fluid, finite element method, FEM, optimization, differntial evolution, DE, actuator
Objavljeno v DKUM: 22.05.2024; Ogledov: 64; Prenosov: 6
.pdf Celotno besedilo (4,69 MB)
Gradivo ima več datotek! Več...

Szeged-like entropies of graphs
Matthias Dehmer, Frank Emmert-Streib, Niko Tratnik, Petra Žigert Pleteršek, 2022, izvirni znanstveni članek

Ključne besede: Szeged entropy, Mostar entropy, PI entropy, cut method, quotient graphs, sensitivity of a topological descriptor
Objavljeno v DKUM: 20.05.2024; Ogledov: 30; Prenosov: 2
.pdf Celotno besedilo (3,17 MB)
Gradivo ima več datotek! Več...

Vial wall effect on freeze-drying speed
Matjaž Ramšak, Matjaž Hriberšek, 2024, izvirni znanstveni članek

Opis: The vial wall thermal conductivity and thickness effect on freeze-drying speed is simulated. A 2D axisymmetric numerical simulation of Mannitol freeze-drying is employed using the boundary element method. The originality of the presented approach lies in the simulation of heat transfer in the vial walls as an additional computational domain in contrast to the typical methodology without a vial wall. The numerical model was validated using our measurements and the measurements from the literature. Increasing the glass vial thickness from 1 mm to 2 mm has been found as the major factor in primary drying time, increasing the gravimetrical Kv up to 20 % for all the simulated chamber pressures. The effect of thermal conductivity was simulated using a polymer and aluminium vial replacing the standard glass vial of the same thickness. The polymer vial‘s decreased Kv value is 5.6 % at a low chamber pressure of 50 mTorr, and 12.2 % at 400 mTorr, which is in excellent agreement with the experiment. Using higher conductivity materials, for example, aluminium, only 3.7 % and 2.3 % Kv increase were computed for low and high chamber pressures respectively.
Ključne besede: freeze-drying, lyophilization speedup, vial heat conductivity, vial wall thickness, boundary element method
Objavljeno v DKUM: 16.04.2024; Ogledov: 139; Prenosov: 8
.pdf Celotno besedilo (1,88 MB)
Gradivo ima več datotek! Več...

The cut method on hypergraphs for the Wiener index
Sandi Klavžar, Gašper Domen Romih, 2023, izvirni znanstveni članek

Opis: The cut method has been proved to be extremely useful in chemical graph theory. In this paper the cut method is extended to hypergraphs. More precisely, the method is developed for the Wiener index of ▫$k$▫-uniform partial cube-hypergraphs. The method is applied to cube-hypergraphs and hypertrees. Extensions of the method to hypergraphs arising in chemistry which are not necessary ▫$k$▫-uniform and/or not necessary linear are also developed.
Ključne besede: hypergraphs, Wiener index, cut method, partial cube-hypergraphs, hypertrees, phenylene, Clar structures
Objavljeno v DKUM: 11.04.2024; Ogledov: 109; Prenosov: 5
.pdf Celotno besedilo (318,42 KB)
Gradivo ima več datotek! Več...

Innovative approaches to wear reduction in horizontal powder screw conveyors : a design of experiments-guided numerical study
Marko Motaln, Tone Lerher, 2024, izvirni znanstveni članek

Opis: Numerical simulations play a vital role in the modern engineering industry, especially when faced with interconnected challenges such as particle interactions and the structural integrity of conveyor systems. This article focuses on the handling of materials and emphasizes the importance of using parametric numerical analysis to improve efficiency, reduce wear, and enhance the structural integrity of horizontal screw conveyors. Through the utilization of the Design of Experiments, we systematically investigated critical parameters such as screw pitch, clearance, wear, rotational velocity, and additional structural factors. This examination was carried out within a well-defined parametric framework, utilizing a combination of software tools provided by the Ansys suite and Minitab. The findings demonstrate the effectiveness of the Design of Experiments analysis in achieving improved performance and provide valuable insights for engineers and researchers involved in the design of conveyor systems. Furthermore, this comprehensive approach clarifies how conveyor systems respond to changes in parameters and highlights the complex interaction between transported particles and the conveyor system. We present a detailed analysis that clarifies the complex relationships and dependencies among different parameters, providing engineers and researchers with valuable insights. By understanding the interactions of these factors, the methodology provides not only results but also a strategic framework for advancing conveyor system design and engineering practices.
Ključne besede: discrete element method, design optimization, horizontal screw conveyors, parametric study, conveying equipment, bulk handling, bulk solids, abrasive wear, screw conveyor, FEA, performance analysis
Objavljeno v DKUM: 09.04.2024; Ogledov: 155; Prenosov: 20
.pdf Celotno besedilo (10,51 MB)
Gradivo ima več datotek! Več...

Optimization of chaboche material parameters with a genetic algorithm
Nejc Dvoršek, Iztok Stopeinig, Simon Klančnik, 2023, izvirni znanstveni članek

Ključne besede: Chaboche material model, parameter optimization, genetic algorithm, finite element method
Objavljeno v DKUM: 04.04.2024; Ogledov: 75; Prenosov: 7
.pdf Celotno besedilo (3,62 MB)
Gradivo ima več datotek! Več...

Measurements of Small Frequency Differences by Dual Mode 4 MHz Quartz Sensors
Vojko Matko, 2023, izvirni znanstveni članek

Opis: We proposed a method for measuring frequency differences of the order of a few Hz with an experimental error lower than 0.0001% by using two 4 MHz quartz oscillators, the frequencies of which are very close (a few 10 Hz difference) due to the dual mode operation (differential mode with two temperature-compensated signal frequencies or a mode with one signal and one reference frequency). We compared the existing methods for measuring frequency differences with the new method which is based on counting the number of transitions through zero within one beat period of the signal. The measuring procedure requires equal experimental conditions (temperature, pressure, humidity, parasitic impedances etc.) for both quartz oscillators. To ensure equal resonant conditions for oscillation two quartz crystals are needed, which form a temperature pair. The frequencies and resonant conditions of both oscillators must be almost equal, which is achieved by an external inductance or capacitance. In such a way, we minimized all the external effects and ensured highly stable oscillations and high sensitivity of the differential sensors. The counter detects one beat period by an external gate signal former. By using the method of counting transitions through zero within one beat period, we reduced the measuring error by three orders of magnitude, compared to the existing methods.
Ključne besede: small frequency difference measurement, temperature-compensated quartz sensors, differential sensors, quartz oscillators, transitions-through-zero method
Objavljeno v DKUM: 26.03.2024; Ogledov: 261; Prenosov: 245
.pdf Celotno besedilo (4,21 MB)
Gradivo ima več datotek! Več...

Iskanje izvedeno v 2.75 sek.
Na vrh
Logotipi partnerjev Univerza v Mariboru Univerza v Ljubljani Univerza na Primorskem Univerza v Novi Gorici