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1.
Slow growth storage of Berula erecta in vitro - effect of sucrose, sorbitol and temperature
Jana Ambrožič-Dolinšek, Sanja Oblonšek, Terezija Ciringer, 2022, izvirni znanstveni članek

Opis: It has been established that in vitro storage of Berula erecta (Huds.) Coville by slow growth would rationalize the culture maintenance by reducing the number of transfers to fresh medium. Attempts of slow growth were made while maintaining viability by adding sugars and sugar alcohols to the MS medium and lowering the culture temperature in the growth chambers. The effect of low temperatures (13°C and 4°C), different combinations and concentrations of sorbitol (20, 40 g L-1) and sucrose (30, 40 g L-1), and light was tested to determine the viability and ability of B. erecta to recover growth. Increasing sucrose concentration did not inhibit or slow growth. At 23 ± 2°C, the addition of 20 g L-1 sorbitol successfully inhibited growth, while the addition of 40 g L-1 sorbitol resulted in plant senescence after two months of culturing. Storage of B. erecta at 13°C did not effectively inhibit growth and recovery ability in any treatment. The most effective way to maintain B. erecta for long-term slow growth storage in tissue culture while retaining a high level of viability with minimal growth was to culture the plants at 4°C in the dark. This kept the plants viable and capable of regeneration for several months.
Ključne besede: slow growth storage, viability, sucrose, sorbitol, temperature, Berula erecta
Objavljeno v DKUM: 23.05.2024; Ogledov: 49; Prenosov: 2
.pdf Celotno besedilo (878,32 KB)
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Carbon-free heat production for high-temperature heating systems
Sven Gruber, Klemen Rola, Danijela Urbancl, Darko Goričanec, 2023, izvirni znanstveni članek

Opis: The article presents a new carbon-free heat production technology for district heating, which consists of a combined heat and power generation fuel cell (FC CHP) with CO2 capture and a two-stage cascade high-temperature heat pump (TCHHP). The FC generates heat and electricity, the latter being used to drive the compressors of the TCHHP. During the winter period, the water temperature achieved can occasionally be too low, so it would be heated up with hydrogen gas boilers. The hydrogen would be produced by reforming natural gas, synthetic methane, or biogas. The results are presented with natural gas utilization—the ratio between the obtained heat flow transferred directly to the water for district heating and the input heat flow of natural gas. In the case of a return water temperature of 60 °C and district heating temperature of 85 °C, the TCHHP, whose heat source is groundwater, achieves plant efficiency of 270.04% in relation to the higher heating value (HHV) and 241.74% in relation to the lower heating value (LHV) of natural gas. A case with a TCHHP whose heat source is low-temperature geothermal water achieves a plant efficiency of 361.36% in relation to the HHV and 323.49% in relation to the LHV.
Ključne besede: carbon-free, decarbonization of district heating systems, fuell cell, high-temperature district heating, high-temperature heat pump
Objavljeno v DKUM: 10.05.2024; Ogledov: 90; Prenosov: 4
.pdf Celotno besedilo (3,32 MB)
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4.
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)
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5.
Loss of oxygen atoms on well-oxidized cobalt by heterogeneous surface recombination
Domen Paul, Miran Mozetič, Rok Zaplotnik, Jernej Ekar, Alenka Vesel, Gregor Primc, Denis Đonlagić, 2023, izvirni znanstveni članek

Opis: Calorimetry is a commonly used method in plasma characterization, but the accuracy of the method is tied to the accuracy of the recombination coefficient, which in turn depends on a number of surface effects. Surface effects also govern the kinetics in advanced methods such as atomic layer oxidation of inorganic materials and functionalization of organic materials. The flux of the reactive oxygen atoms for the controlled oxidation of such materials depends on the recombination coefficient of materials placed into the reaction chamber, which in turn depends on the surface morphology, temperature, and pressure in the processing chamber. The recombination coefficient of a well-oxidized cobalt surface was studied systematically in a range of temperatures from 300 to 800 K and pressures from 40 to 200 Pa. The coefficient increased monotonously with decreasing pressure and increasing temperature. The lowest value was about 0.05, and the highest was about 0.30. These values were measured for cobalt foils previously oxidized with oxygen plasma at the temperature of 1300 K. The oxidation caused a rich morphology with an average roughness as deduced from atomic force images of 0.9 µm. The results were compared with literature data, and the discrepancy between results reported by different authors was explained by taking into account the peculiarities of their experimental conditions.
Ključne besede: heterogeneous surface recombination, recombination coefficient, cobalt, cobalt oxide, temperature dependence, pressure dependence, plasma, oxygen
Objavljeno v DKUM: 26.03.2024; Ogledov: 131; Prenosov: 17
.pdf Celotno besedilo (3,59 MB)
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6.
Development of the smart T-shirt for monitoring thermal status of athletes
Sandra Stojanović, Jelka Geršak, Suzana Uran, 2022, izvirni znanstveni članek

Opis: Athletes are often subjected to a great physical strain during training and competition. Sport activities performed in hot and humid conditions may result in different heat illnesses with mild or fatal consequences. Against this background it is important to know the thermal state of athletes during physical activity. This article presents the development of a smart T-shirt for monitoring the thermal status of an athlete. The smart T-shirt was created by embedding an electronic system with temperature and humidity sensors that allows the measurement of temperature and the relative humidity of the microclimate. A smart T-shirt is comfortable, and integrated sensors and electronics do not affect wearing comfort. A good concurrence between the temperature and humidity results from using the smart T-shirt, and thus the medical device was achieved. Data obtained can be of great importance to the sports staff who will be able to monitor the athletes' thermal state during matches and competitions.
Ključne besede: smart T-shirt, microclimate temperature, relative humidity of the microclimate
Objavljeno v DKUM: 26.03.2024; Ogledov: 106; Prenosov: 10
.pdf Celotno besedilo (1,34 MB)
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7.
Recombination of oxygen atoms on the surface of oxidized polycrystalline nickel : temperature and pressure dependences
Domen Paul, Miran Mozetič, Rok Zaplotnik, Jernej Ekar, Alenka Vesel, Gregor Primc, Denis Đonlagić, 2023, izvirni znanstveni članek

Opis: The recombination of neutral oxygen atoms in the ground state on the oxidized nickel samples was studied experimentally in the range of pressures where the maximum density occurs in weakly ionized low-pressure oxygen plasma, i.e. between 40 and 200 Pa. The recombination coefficient was determined in the flowing afterglow. The source of oxygen atoms was plasma sustained in a quartz tube of inner diameter 4.7 mm by a microwave discharge in the surfatron mode. The recombination coefficient was determined in the afterglow chamber, which was a Pyrex tube with an inner diameter of 36 mm. The density of oxygen atoms in the afterglow chamber was varied by adjusting the discharge power, the gas flow, the pressure, and the position of a recombinator. Such flexibility of the experimental system enabled adjustment of the temperature of the oxidized nickel samples independently from the O-atom density in its vicinity or other parameters. The density of oxygen atoms in the afterglow chamber at various system parameters was determined by the Šorli method, which is reliable, and has an accuracy of about 20%. The recombination coefficient was determined by calorimetry. The coefficient was inversely proportional to the square root of the pressure and exponentially to the sample temperature. Systematic measurements performed at various pressures and temperatures enabled empirical formula, which were explained qualitatively by recombination kinetics.
Ključne besede: heterogenous surface recombination, recombination coefficient, nickel, nickel oxide, temperature
Objavljeno v DKUM: 25.03.2024; Ogledov: 121; Prenosov: 14
.pdf Celotno besedilo (2,44 MB)
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8.
An All-Fiber Fabry–Pérot Sensor for Emulsion Concentration Measurements
Simon Pevec, Janez Kunaver, Vedran Budinski, Matej Njegovec, Denis Đonlagić, 2023, izvirni znanstveni članek

Opis: This paper describes a Fabry-Perot sensor-based measuring system for measuring fluid composition in demanding industrial applications. The design of the sensor is based on a two-parametric sensor, which enables the simultaneous measurement of temperature and refractive index (RI). The system was tested under real industrial conditions, and enables temperature-compensated online measurement of emulsion concentration with a high resolution of 0.03 Brix. The measuring system was equipped with filtering of the emulsion and automatic cleaning of the sensor, which proved to be essential for successful implementation of a fiber optic RI sensor in machining emulsion monitoring applications.
Ključne besede: optical fiber sensors, Fabry–Pérot interferometer, refractive index, temperature, emulsion concentration
Objavljeno v DKUM: 06.02.2024; Ogledov: 207; Prenosov: 16
.pdf Celotno besedilo (4,44 MB)
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9.
Načrtovanje sistema vodenja termoelektričnega hladilnika : diplomsko delo
Alen Merčnik, 2023, diplomsko delo

Opis: V diplomskemu delu smo načrtali sistem vodenja termoelektričnega hladilnika. Termoelektrični hladilniki so naprave, ki uporabljajo Peltierjev pojav za hlajenje manjših naprav in zagotavljajo njihovo učinkovito delovanje. V načrtanem sistemu smo uporabili termoelektrični hladilnik manjših dimenzij in omejitvijo napajelne napetosti 3V oz. omejitvijo maksimalnega napajalnega toka 3A. Za učinkovito hlajenje se zahteva konstanten napjalni tok. Iz tega razloga smo uporabili namensko integrirano vezje ADN8831 in digitalno vodenje s pomočjo MAX5715 kot DAC pretvornik. Opravljen je bil preizkus vodenja izbranega termoelektričnega hladilnika, ki je pokazal dobro regulacijo temperature.
Ključne besede: termoelektrični hladilnik, Matlab, regulacija temperature, Peltierjev pojav, regulacija
Objavljeno v DKUM: 06.02.2024; Ogledov: 390; Prenosov: 39
.pdf Celotno besedilo (2,27 MB)

10.
Urban greening as a cooling tool towards the heat island effect
Anja Bubik, Lucija Kolar, 2019, izvirni znanstveni članek

Opis: Roofs, as the top layer of the urban environment, significantly contribute to overheating and creating a heat island, which is known as one of the most critical global warming effects. There are several ways to mitigate the effects of such heat islands, among which greening is the most natural, sustainable solution, and also economically acceptable and socially valued principle. Vegetation is known to significantly improve the urban microclimate and directly reduce the effect of the urban thermal core. At the Environmental Protection College in collaboration with the Institute Complementarium, both based in Slovenia, we conducted a pilot experiment to evaluate greening, in our case the principle of a flat green roof, as an effective and promising approach for reducing an urban heat island and its effects. Temperature measurements have shown that the green surface can lower both the surface temperature itself (e.g., the roof) and the air surrounding the green surface. We have presented an initial pilot case, which is planned to be upgraded in the future to confirm our current results and assumptions. In addition, we summarized data showing that Velenje is, in view of annual higher average temperatures, a highly suitable urban environment for the introduction of greening principles on the top urban layers.
Ključne besede: air temperature, greening principle, heat island effect, pilot study, urban environment
Objavljeno v DKUM: 05.12.2023; Ogledov: 311; Prenosov: 4
.pdf Celotno besedilo (1,31 MB)
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