Prediction of Soc in Calcic Chernozem in the Steppe Zone of Ukraine Using Brightness and Colour Indicators

Soil organic carbon (SOC) is an important component of any soil which determines many of its properties. Nowadays, more and more attention is being paid to the SOC content determination in soils by not using the conventional, time-consuming and expensive technique, but by using colour image processing of soil samples. In this case, even the camera of modern smartphones can be used as an image source, making this technique very convenient and practical. However, it is important to maintain certain standardised conditions (light intensity, light incidence angle, etc.) when capturing the images of soil samples. In our opinion, it is best to use a regular scanner for this purpose, with subsequent image processing by graphic programs (e.g., Adobe Photoshop). To increase the reliability of the colour information obtained in this way, it is desired (if possible) to use a spectrograph or a monochromator in the subsequent calculation of reflection or brightness ratios. It is these two approaches that we have implemented in our work. As a result of the experiment, the values of brightness ratios (at 480, 650 and 750 nm wavelengths and integral brightness ratio), colour indicators (the hue, saturation and value [HSV], red, green and blue [RGB], CIE L*a*b* and cyan, magenta, yellow and key [CMYK] systems) and SOC content in Calcic Chernozem samples of the steppe zone of Ukraine were obtained. Using correlation analysis of the dataset, the existence of direct (r = 0.88–0.90) and inverse close relationships (r = −0.75–0.90) between SOC, values of brightness ratios and colour indicators of the soil samples were established. This allows us to develop predictive models. Statistical analysis showed that the models were significant when they were based on the values of brightness ratios at 650 nm wavelength, integral brightness ratio, V indicator in HSV system, R, G and B indicators in RGB system, C, M and K indicators in CMYK system and L* and b* indicators in L*a*b* system. The subsequent calculation of variation coefficients showed that the largest variability was observed in SOC indicators (CV = 0.72) and slightly less variability in the K index of CMYK system and brightness ratio values at 650 nm wavelength (CV = 0.67 and 0.53, respectively). Based on this, we believe that the models y = 0.0188 + 0.0535*x (x is the value of the K index in CMYK system) and y = 5.0716 – 3.2255*log10(x) (x is the value of brightness ratio at 650 nm wavelength) were the most statistically significant and promising parameters for determining SOC content (y in these equations) in Calcic Chernozem samples of the steppe zone of Ukraine.

Bit Error Performance of APD and SPAD Receivers in Optical Wireless Communication

This review concentrates on the state-of-the-art hardware-oriented receiver aspects for optical wireless communication (OWC), and points to the importance of BER performance analysis and modeling in presence of non-perpendicular light incidence. Receivers in OWC networks for 6G applications have to work for strongly different light incidence angles, to allow the formation of connections to locally separated transceivers without the need for rotation units and accurate adjustment. In turn, and in combination with fully integrated optical receivers, reduction of cost and increased comfort can be achieved. Fully integrated [bipolar] complementary metal-oxide-semiconductor ([Bi]CMOS) receivers with on-chip avalanche photodiodes (APDs) and single-photon avalanche diodes (SPADs) are presented and their performance in optical wireless communication is summarized. Impressive data rates up to 2 Gbit/s and free-space transmission distances up to 27 m at bit error ratios (BER) below 10−9 are reached with linear-mode APD receivers. The importance of optical interference in the isolation and passivation stack on top of the integrated photodiodes is illuminated. To be able to predict the dependence of the BER of single-photon avalanche diode (SPAD) receivers on the light incidence angle, a model, which includes a model for the photon detection probability and a standing-wave model for the isolation and passivation stack, is extended. The dependence of the BER on the light incidence angle onto the photodiodes is investigated by electromagnetic simulation for optical transmission of the layers on top of the photodiode, device simulation for the avalanche triggering probability and BER modeling with MATLAB. It is found that incidence angles up to 30° have moderate influence on the BER and that the BER degrades significantly for incidence angles larger than 50°.

Studying the Effect of Light Incidence Angle on Photoelectric Parameters of Solar Cells by Simulation

It is crucial to examine the dependence of photoelectric parameters of solar cells on the light incidence angle. In the present study, two solar cell models have been developed using the Sentaurus Technology Computer-Aided Design software package. The light spectrum AM1.5 has been directed on the frontal surface of solar cells at different angles. It has been found that the angular coefficient of the photoelectric parameters of a solar cell with nanoparticles included, is two times more than that of a simple solar cell. Besides, it has been found that the efficiency of platinum nanoparticles induced solar cells is 2.15 times greater than simple solar cell efficiency. When the light incidence angle has been varied from 0 to 60 degrees, the short-circuit current has changed by 11% for simple solar cells and by 10% for solar cells with nanoparticles. Further, it has been observed that the variation of power for simple solar cells is 12.5%, while it is 10.5% for solar cells with nanoparticles. In addition, the short-circuit current of solar cells with nanoparticles has been found to be linear within a light incidence angle ranging from 0 to 60 degrees.

Destruction of Epoxy Coatings under the Influence of Climatic Factors

The paper presents investigation results of climatic as well as environmental factors influence on surface state of three-layer epoxy coatings. A three-year investigation documented substantial destruction of coating surface layers. In particular, a significant increase of aged coating surface roughness, evaluated on the basis of Ra and Rz parameters, was observed. Studies made with SEM corroborated a delamination as well as pigment and filler crumbling from surface layers of coatings. In the final period of ageing craters and superficial cracks appeared in the coating structure. Destruction of aged coating surfaces contributed to their gloss loss by over 98% (for light incidence angle α = 60o) decreasing in this way coating decorative properties.

External Reflection Infrared Spectroscopy of Anisotropic Adsorbate Layers on Dielectric Substrates

Monolayers of octadecylsiloxane were formed on native silicon (Si/SiO2) and glass surfaces by adsorption from dilute solutions of octadecyltrichlor osilane and were investigated by polarization- and angle-dependent external reflection infrared spectroscopy. In contrast to metal substrates, both the parallel and perpendicular vibrational components of the adsorbate can be detected on these dielectric surfaces. The monolayer reflection spectra show significant changes as a function of the light incidence angle and the polarization of the infrared radiation, which contain detailed information on the surface orientation of the film molecules. Spectral simulations based on classical electromagnetic theory yield an average 10° tilt angle of the hydrocarbon chains with respect to the surface normal on both silicon and glass surfaces. Despite this apparent structural identity of the monolayer films on silicon and glass, significant differences are observed in the monolayer reflection spectra resulting from purely optical effects of the substrate.