The purpose of the piece The Strategikon as a source — Slavs and Avars in the eyes of Pseudo- Maurice, current state of research and future research perspectives is to demonstrate what the author of Strategikon knew about the Slavs and Avars and review the state of research on the chapter of the treatise that deals with these two barbarian ethnicities. As a side note to the description of contemporary studies of Strategikon, the piece also lists promising areas of research, which have not yet received proper attention from scholars.

In view of the world’s recent changes in the mineral market, it is becoming increasingly important to ensure the sustainable and secure supply of raw materials, both within the European Union and in other high-developed countries. In response to this global challenge, as part of the European Commission’s Horizon 2020 Program for Research & Innovation, the 36-month INTRAW project was launched in February 2015 to foster international cooperation on raw materials. The EU-funded INTRAW project was set up to map and develop new cooperation opportunities related to raw materials between the EU and other technologically advanced countries, such as: Australia, Canada, Japan, South Africa and the United States. The first stage of the project was a review of conditions for the stable supply of raw materials from primary and secondary sources in selected countries: the United States, Canada, Australia, South Africa and Japan. The results of the work are two groups of comprehensive reports. The first of these is a broad contextual analysis of geological, environmental, political, technical -economic and social factors conducive to the effective management of mineral resources. The second group is operational reports, carried out in three thematic blocks: industry and trade, research and innovation, education. The analysis clearly shows that the basis for effective action in this area is a stable political, economic and institutional environment, which is friendly to mining and new entities wishing to invest in modern technologies, the exploration and exploitation of deposits. Investors are encouraged by tax regulations, sometimes also by direct government financial support and efficient licensing procedures. The well-defined protection of property rights, also for deposits is equally important. Selected aspects of a wide analysis of determinants of competitiveness for these countries were presented in the article below.

The paper presents the statical research tests of rod bolt made of plastic with a length of 5.5 m, which were performed in a modern laboratory test facility at the Department of Underground Mining of the University of Science and Technology. Innovative The Self-excited Acoustic System (SAS) used to measure stress changes in the bolt support was characterized. The system can be used for the non-destructive evaluation of the strain of the bolt around the excavations as well as in tunnels. The aim of the study was to compare the re-sults recorded by two different measuring systems, thanks to which it will be possible to assess the load of long bolt support by means of the non-destructive method. The speed and simplicity of measurement, access to the sensors, accuracy of measurement and reading should be kept in mind in determining the load of rock bolt support . In addition, the possibility of damage to the sensor as a re-sult of technological or natural hazards should also be taken into account. In economic conditions, the „technical - balance laws of production”, which ex-cludes the use of load sensors on each bolt must be preserved. The use of indi-vidual load sensors of rock bolt support for the boundary state, allows appro-priate protection actions of the mining crew against sudden loss of excavation stability to be taken. The paper presents two basic effects used in the ultrasonic measurement sys-tem. The first result was the existence of stable limit cycle oscillations for posi-tive feedback. This effect is called the self-excited effect. The second effect is called the elasto-acoustic effect. It means that with the change of elastic stress-es in the material bring the change of the speed of propagation of the wave. In this connection, the propagation time between measuring heads is also changed. This effect manifests itself in the change in the oscillation frequency of the self-excited system. For this reason, by measuring the frequency of self-excited oscillation, it is possible to indirectly determine the level of effort of the tested material.

In recent years, the Budryk Coal Mine (KWK Budryk) reached the mining depth of 1300 m, where there is about 160 million tons of coal, including 120 million tons of coking coal (type 35). The task of the Coal Processing Plant complex modernization was undertaken. The article presents the modernization of coal screening, classification and dewatering systems at the KWK Budryk Processing Plant and the implementation of screening of PROGRESS ECO sp. z o.o. SK. The modernization project defined the following technical requirements for all screens in the KWK Budryk Coal Processing Plant extension project:

- Vibrating screens with a linear type drive with a drive unit placed on the drive beam of the trommel screen in the form of vibration generators;

- Screen drives equipped with a starting-braking device;

- The use of main screen drive bearings with a nominal service life of at least 40,000 man-hours;

- All work surfaces made of materials with a strength of up to 80 mm grain and abrasion resistance; side strips and sieves fixed in a way ensuring trouble-free operation, and at the same time quick and easy replacement;

- Sheets made of stainless steel;

- Side walls, beams and other elements attached to them connected with screws using a system protecting against corrosion and elements separation;

- The use of a work parameters monitoring and visualization system, i.e.

- pitch of the riddle,

- bearing operating temperatures and the condition of their wear.

Three types of screens were provided:

- PWP1-1Z-2,8x6,0 screeners that alternatively perform sieving or desliming processes,

- PWP1-2.4x6.0 screening machines performing desliming processes,

- PWP1-2.0x6.0 screens performing the classification process.

This article is an analysis, based on school textbooks, of the norms governing literacy practices in elementary education. These latter are treated as a kind of ritual: the symbolic behaviour impacting not so much the manner of the mental representation of reality as the corporeal-perceptive organization of experience. The aim of the article is to show that (1) contrary to classic literacy theory, writing is not always a tec because in many situational and institutional contexts writing practices are not instrumental but ritual practices, and (2) writing is not solely a tool of the intellect corresponding to a set manner of conceptualizing the world, language, and the self, but also a kind of social tool for the discipline of the body: the acquiring of a certain corporeal-perceptive disposition.

Organized security groups are operational on board some commercial vessels. These are professional units comprised of personnel whose only duties are to ensure that the overall physical safety of the vessel is maintained. Since maritime law does not take a position regarding such services, it can be concluded that the formation and maintenance of them is legal. Nevertheless, in order for potential actions taken by such groups to be acknowledged as legal, they must not exceed repelling direct attacks on the guarded vessel. It is not likely that attempts will be made in the nearest future to bring this issue under the detailed regulation of international law. The principles guiding the actions o f security groups are governed by the laws of the country of the ship’s flag. The role of the security officer has increased significantly within the hierarchy of the ship’s command. On the majority of large passenger vessels this is now a full-time position, and the person in charge of security is directly subordinate to the captain.

This paper presents the design of digital controller for longitudinal aircraft model based on the Dynamic Contraction Method. The control task is formulated as a tracking problem of velocity and flight path angle, where decoupled output transients are accomplished in spite of incomplete information about varying parameters of the system and external disturbances. The design of digital controller based on the pseudo-continuous approach is presented, where the digital controller is the result of continuous-time controller discretization. A resulting output feedback controller has a simple form of a combination of low-order linear dynamical systems and a matrix whose entries depend nonlinearly on certain known process variables. Simulation results for an aircraft model confirm theoretical expectations.

The paper presents areas where the EBITDA measure is used in coal companies. The metric and the ratios where it is utilized are employed to assess companies and management efficiency, hence they are used as criteria for rewarding board members. EBITDA-based ratios are also used to evaluate the profitability of company restructuring and its goodwill in mergers and acquisitions. EBITDA, also tends to be used to value companies on the capital market. It is a good tool for efficiency assessment in coal companies with relatively stable fixed assets and small share of intangible assets, which amortized over short periods of time could interfere the comparability of relations based on this measure. The comparability is also disturbed by large investment expenditure incurred in the short term. This does not apply to the mining industry, in which investment cycles are long, last several years and expenditures are spread over time. In addition, the rate of technical progress imposing the need to implement large technology projects is not high compared to technology companies with high development dynamics.

EBITDA based ratios were used to assess a number of listed coal companies. The analysis revealed that the profit/loss of these companies is mainly determined by coal prices. The cost of coal mining is 90% fixed and projects undertaken to reduce it bear fruit only over the long term. Cyclically changing coal prices cause major losses in companies when prices are low, which leads to bankruptcies or a need to restructure. After a period of decline in 2014–2016, the profit/loss of Polish coal companies as well as companies from around the world improved in 2017–2018. T he financial standing of Polish companies was better than that of their counterparts from other parts of the world.