We observe the relationship and causality between cryptocurrencies on one, and commodities, currencies, equity indexes and web search results on the other side. We use prices of Bitcoin and Ethereum for cryptocurrencies, prices of crude oil and gold for commodities, Euro-US Dollar, Euro-Swiss Franc exchange rates for currencies, Dow Jones Industrial Average for market index and Google Trends® data as a measure of worldwide web search results for cryptocurrencies of interest. We find that Bitcoin and web search results correlation went from highly positive to low negative during the COVID-19 period. The results of the study show that the price of Bitcoin and Ethereum can be modelled using different combinations of commodities, currencies, indexes and web search results, with web search results and Dow Jones Industrial Average exhibiting best predictive power both concurrently and one day in advance. Our best performing models were able to explain more than 95% and 90% of Bitcoin and Ethereum price variability respectively. We also find strong evidence of web search traffic impacting both Bitcoin and Ethereum prices at all tested lags, as well as some evidence of gold impact on Bitcoin and EUR/CHF impact on Ethereum.

The use of renewable energy sources is imposed as an imperative for the competitiveness and stable energy policy of companies. The basic production equipment in the "Kreka" coal mine in Tuzla has electrical plants with a total peak load of 12 MW, and the costs for electrical energy exceed €3.5 million annually. The paper analyzes the suitability of infrastructure facilities and devastated areas of the Kreka Coal Mine in Tuzla for the construction of photovoltaic power plants and the effects of such plants. The results of the analysis show a significant resource for the installation of photovoltaic power plants with a capacity of 230 MW. The production of electricity from these photovoltaic power plants enables a reduction of emissions into the air by 190 t/year of particle emissions, by 316.2 •103 t/year of CO2 emissions, by 58.15 t/year of SO2 emissions and by 251.9 t/year of emissions NOx. With the subsidized purchase of electricity, it is possible to return the investment within 6 years.

Optical character recognition represents the mechanical or electronic conversion of handwritten, typed or printed images into coded text. Optical character recognition is widely used as a form of data entry from records that have been printed, and it can include invoices, bank statements, passports and many more. In the research, Optical character recognition reads data from the Re-Captcha dataset of images, converts them into strings, and these strings are used for testing, training and calculating prediction accuracy. The methodologies used are Convolutional neural network and Recurrent neural network. The convolutional neural network consist of neurons that receive data and group them according to similarity. A recurrent neural network cycle can be created between the connections of nodes, allowing the output from nodes to influence the subsequent input to other nodes. For data were used Re-Captcha images, and for the prediction of characters from images was used TensorFlow with Keras. The best results that are produced can be compared between first and last result, where the loss for first result was 20.63 and value loss was 16.45, while last result has loss of 0.56 and value loss of 2.96

There is a growing technological development in intelligent teaching systems. This field has become interesting to many researchers. In this paper, we present an intelligent tutoring system for teaching mathematics that helps students un-derstand the basics of linear programming using Linear Program Solver and Service for Solving Linear Programming Problems, through which students will be able to solve economic problems. It comes down to determining the minimum or maximum value of a linear function, which is called the objective function, according to pre-set limiting conditions expressed by linear equations and inequalities. The goal function and the limiting conditions represent a mathematical model of the observed problem. Working as a professor of mathematics in high school, I felt the need for one such work and dealing with the study of linear programming as an integral part of mathematics. There are a number of papers in this regard, but exclusively related to traditional ways of working, as stated in the introductory part of the paper. The center of work as well as the final part deals with the study of linear programming using programs that deal with this topic.

Eduard von Keyserling wird schon von seinen Zeitgenossen, aber auch während der späteren Rezeption als Autor aufgefasst, dessen Werke thematisch um den kulturellen Verfall seines eigenen Milieus, des deutsch-baltischen Adels, kreisen. Der schwerkranke und blinde Keyserling erscheint dabei selbst als letzte Sprosse seiner Familienlinie. Der deutsch-baltische Adel erweist sich als eine Gesellschaft, die wegen der jahrhundertealten, fast unveränderten Lebensweise beim Aufbruch der Moderne ihrem Untergang entgegenläuft. Die Verfallsstimmung lässt sich dabei durch verschiedene Anzeichen bemerken. Das familiäre und gesellschaftliche Leben dieser Menschen wird von einer Ordnung geprägt, deren Beschützer und Befürworter die alten Schlossherrschaften sind. Diese psychisch immer noch starken Menschen verlieren jedoch an Lebenskraft und blicken oft als Schwerkranke dem bevorstehenden Tod entgegen. Die Pflege der Tradition soll daher an die jüngere Generation vermittelt werden, die jedoch dieser Aufgabe nicht gewachsen ist. Die Jugend hat ebenfalls mit verschiedenen psychischen oder physischen Krankheiten zu kämpfen. Überempfindlichkeit, Reizhunger oder Neurose treiben diese jungen Menschen aus der zwar geborgenen, aber betrübenden familiären Umgebung oder schließen sie noch fester innerhalb der Schlossmauern ein, sodass jegliche äußeren Einflüsse als Bedrohung erscheinen. Beide Fälle sind dabei durch die Verneinung der Wirklichkeit zum Scheitern verurteilt. Als misslungen erweisen sich ebenfalls die häufigen Bestrebungen, über die eigene Sensibilität und Kränklichkeit durch den Genuss des häuslichen Komforts hinwegzutäuschen. Keyserling schildert eine Gesellschaft, die den eigenen Verfall mit einem Schleier des ästhetisch Schönen zu bedecken versucht, dabei jedoch von der Realität immer wieder eingeholt wird.

The paper presents the results of a comparison of brown rendzina and colluvial sinkhole at approximately the same altitudes and the same land use. The sites were located in the Kalati area within the National Park „Una“. More precisely, the places referred to the top of the sinkhole (brown rendzina top) and the bottom of the sinkhole (colluvial soil bottom). The main objective of the research, in addition to the physical and chemical parameters of soil quality, was to determine the distribution of the total content of cadmium (Cd), nickel (Ni) and arsenic (As). The total content of these elements werw observed in composite samples at two depths of 0 – 10 and 0 – 20 cm and horizons profile. Their total content was measured by atomic adsorption spectrometry – AAS. The results were statistically analyzed using Kruskal Walisovog test at the significance level of p ≤ 0.05 using correlation coefficient χ. The results showed a single legality of the distribution of Cd, Ni and As in samples of soil profile, while the average soil samples showed unique legality of the distribution of observed elements.