Energy balance of the photovoltaic system is influenced by many factors. In this article the effect of tilt and azimuth angle changes of the photovoltaic system energy production is analyzed. These parameters have significant impact on the amount of solar radiation which hits on the photovoltaic panel surface and therefore also on the energy absorbed by the module surface. The main aim of research was identification of the optimal position of photovoltaic system installation in the southern Slovakia regions. The experimental apparatus had two setups consisting of polycrystalline photovoltaic modules. The first setup was used for identification of the tilt angle changes in the range (0–90°). The second one was focused on the detection of the azimuth angle effect to the energy production. The measurement results were statistically processed and mathematically analyzed. Obtained dependencies are presented as two-dimensional and three-dimensional graphical relations. Regression equations characterize time relations between the tilt or azimuth angle and the energy produced by the photovoltaic system in Southern Slovakia. Obtained simplified mathematical model was verified by analytical model. Presented models can be used for the dimensioning and optimization of the photovoltaic system energy production.
The paper presents the designed system to measurements of gas sensor transient characteristics. Electrochemical oxygen sensor SK-25F was selected for measurements from point of view application in health care and ensuring human safety in industrial production facilities and laboratories. The aim of this work is to design an automatic system for measuring the transient function G(s) of electrochemical sensors and to identify the mathematic model from a sample of sensors. The automatic measurement system based on a microcontroller for the measurements of dynamical characteristics of gas sensors was designed and developed. The result is transfer function with fit to estimation data higher as 99.48 %. The bandwidth of gas sensors was calculated on average at 0.0285763 Hz with a maximum deviation of 0.34 %. Finally, an algorithm for detecting the exceeding of the frequency range of an electrochemical gas sensor is proposed. Its application is in speed control UAV with the aim of accurate measurements of gases in the air by electrochemical sensors.INDEX TERMS sensors, oxygen, measurement techniques, transfer functions, electrochemical devices, Laplace equations.
This article deals with the regression analysis of the ultrasonic signal amplitude when the character of the reflection surface has been changed from a planar case to a sharp corner case. The experiment was performed at a measurement distance within the interval from 100 mm to 215 mm. A nonlinear correlation between the amplitude of the ultrasound signal and the measured distance was demonstrated. By analyzing the frequency spectra, a poor nonlinear correlation between the maximum frequency component and the distance vector was found for the sharp corner case versus the planar case, which proved similar nonlinear characteristics as the signal amplitude marker. The strong linear correlation in the distance difference vectors in the amplitude analysis of the ultrasound signal confirmed the hypothesis of a direct relationship between the reflection surface geometric characteristic and the polarity of the difference. The ultrasound signal was identified as a 3rd-order dynamic system. The nonlinear correlation of the steady-state values of the modelled transfer functions versus distance likewise shows the characteristic of the polarity difference or character derivative as a quantification marker of the characteristics of the reflection surface from the geometric point of view.
The aim of the presented study was to determine the nutritional properties (dry matter, total protein, ash, and selected amino acid content), antioxidant properties (antioxidant activity; total polyphenol, flavonoid, and phenolic acid content; total carotenoid, chlorophyll, and anthocyanin), and sensory profile (general appearance, flavor, taste, aftertaste, overall acceptability) of pasta enriched with powdered nettle leaves, elderberry fruit, and carrot in additions of 3%. A control variant without the addition of plant material was prepared for comparison of the results. Two of our samples of pasta (with nettle and carrot) had lower calorific values by approximately 17%. However, the energy value of the pasta was not significantly affected by added substances. Electrical properties (resistance, impedance) were also measured, and resistivity was calculated. We found that impedance and resistivity were influenced by added components in pasta. In the frequency range from 20 kHz to 100 kHz, we were able to use the measured dependencies of the mentioned electrical properties to identify the type of addition to the pasta. Correlations exist between the electrical properties and nutritional properties of enriched pasta samples, and could be used to indetify value-added pasta in processing chain digitalization.
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