This article presents values of porosity and compression strength of hard coals from the area of the Upper Silesian Coal Basin. The change of the stage of carbonification, which results from conversion of coal substance in the process of coalification, is a source of many changes in the structure of coal. These changes exert influence on values of physical parameters, including the values of porosity and strength. Porosity and compression strength change with the degree of carbonification, a result of the depth of deposition. This study determined the values of effective porosity of coals and their strength considering the age chronology of coal seams and the depth of their occurrence. It examined coals of the Cracow Sandstone Series, the Mudstone Series, the Upper Silesian Sandstone Series, and the Paralic Series from depths ranging from about 350 m to 1200 m. The authors have shown that effective porosity of the Upper Silesian coals changes for particular stratigraphic groups and assumes values from a few to a dozen or so per cent, while compression strength from several to several dozen megapascals. It has been observed, from a chronostratigraphic perspective, that there is a shifting of the upper and lower limits of intervals of porosity variations towards higher values for younger coals. With the increase in compression strength, value of porosity in particular stratigraphic groups generally decreases. However, no regular changes were observed in mean, uniaxial compressive strength with the increase in the age of subsequent stratigraphic groups. On the other hand, for bright coal and semi-bright coal, a visible decrease in compression strength with the depth of deposition of strata was observed.

Most satellites stationed in space use catalytic propulsion systems for attitude control and orbit adjustment. Hydrazine is consumed extensively as liquid monopropellant, in the thrusters. Catalytic reactor is the most important section in the catalytic thruster. Ammonia and nitrogen gases are produced as a result of complete catalytic decomposition of hydrazine in the reactor, causing an increase in temperature and a rise in specific impulse. Ammonia is subsequently decomposed, leading to nitrogen and hydrogen gases. Decomposition of ammonia leads to a decrease in temperature, molecular weight and specific impulse. The latter phenomenon is unavoidable. The effect of ammonia decomposition on the reactor temperature, molecular weight of gaseous products and conclusively on specific impulse was studied in this article. At adiabatic state, thermodynamic analysis revealed that the maximum and minimum temperatures were 1655 K and 773 K, respectively. The highest molecular weight was obtained at ammonia conversion of zero and the lowest when ammonia conversion was 100%. The maximum specific impulse (305.4 S) was obtained at ammonia conversion of zero and completely conversion of ammonia, the minimum specific impulse (about 213.7 s) was obtained. For specific impulse, the result of thermodynamic calculation in this work was validated by the empirical results.

According to various sources, between approximately 8.5 and even 10 million tons of Russian coal entered Polish market in 2022, which was mainly used for heating purposes by heating companies and private households (especially in the northern regions of the country). A ban on the continuation of these imports requires the identification of other sources of fuel – these could be either imports from other countries or an increase in mining volumes by domestic mines. However, both of these alternatives require a certain amount of time to be realized. Finding new foreign suppliers entails new contracts, which can be all the more difficult as many other countries, like Poland, no longer want to buy Russian coal. And then there is the issue of negotiating appropriate prices.
A possible decision to increase domestic mining is linked to other problems. This requires, first and foremost, that new portions of the deposits that could be mined be made available and cut in advance, which often entails several years of underground roadworks and significant financial outlays for their implementation and for the appropriate technical equipment of the newly prepared mining faces. With appropriate financial support from the state, this may be possible but not in every mine as there are a number of other considerations that determine the volume of extraction that can be achieved, particularly if there is a desire to increase it.
The aim of this publication is to present, analyse and identify factors that directly influence the volume of hard coal production, taking into account the dynamically changing market environment.

In the process of extraction and enrichment of coal waste, considerable quantities of waste material are produced, mainly the gangue and coal sludge, considered as waste or raw material. The main directions of the management development of the waste rock are the production of aggregates, the production of energy products and the liquidation works in hard coal mines and the filling of excavations. The paper proposes the extension of these activities to the use of waste material. The possibility of using aggregates or extractive waste to fill open-pit excavations has been proposed, also in areas within the reach of groundwater and the possibility of building insulation layers of waste material and the production of mixtures of hard coal sludge and sewage sludge to produce material with good energy properties. The analysis was based on the author’s own research and literature data related to selected parameters of waste material. This paper presents our own preliminary studies on the amount of combustion heat and the calorific value of coal sludge combined with other wastes such as sewage sludge. The proposed methods and actions are part of the current directions of development, but they allow the extension of the scope of use of both extractive waste and products produced on the basis of gangue or coal sludge. Due to the frequent lack of the stable composition of these materials, their current properties should be assessed each time before attempting to use them. The fact that it is important to continue research to promote existing economic use and to seek new activities or methods has been concluded.

For years, the Polish hard coal mining has been struggling with the problem of fire hazards in

areas with coal residue, mainly in goafs. Currently, a common method of limiting this hazard is the

fire prevention involving use of fine-grained hydromixtures based on power generation waste, mainly

fly ashes. The hydromixture is introduced into the caving zone created by the advancement of exploitation

face and its task is to fill in voids, limiting the possibility of access to the mine air oxygen to

a minimum. The first part of the article presents theoretical fundamentals of determining the parameters

of gravitational hydraulic transport of water and ash hydromixtures used in the mining pipeline

systems. Each hydromixture produced based on fine-grained wastes is characterized by specified

rheological parameters that have a direct impact on the future flow parameters of a given pipeline

system. Additionally, the gravitational character of the hydraulic transport generates certain limitations

concerning the so-called correct hydraulic profile of the system in relation to the applied hydromixture

characterized by required rheological parameters that should ensure safe flow at a correct

efficiency. This paper shows an example of optimisation of the composition of a selected fly ash-water

hydromixture in relation to its capacity for hydrotransport in gravity pipeline installations, as well as

the amount of excess water that will always drain from the location of feeding the hydromixture to

the underground workings.

The article is an attempt to define reduction – a phenomenological methodological device – as the beginning of philosophy. The author considers such questions as: What motivates a phenomenologist to do reduction? Can one speak of philosophy before reduction? What is the essence of reduction? To answer these questions the author refers to Edmund Husserl and Jan Patočka, and tries to show that reduction is to be understood as an unmotivated expression of philosopher’s determination to overcome evidence inherent to natural attitude. The author argues that reduction enables one to perform a conceptualization of the world as such. Finally, reduction is defined as an attempt to take thinking seriously.

For this reason the present paper is first illustrating the evolution of thought ± from hagiography to hagiology. The question is articulated about the justified legitimacy of the introduction of the notion of "hagiology". The distinctness of the subject of research, which itself often demands application of the new methods, certainly proves the right to introduce the notion of "hagiology" into hitherto existing hagiographical researches. Having this on mind, the next question arises: how far the subjects of hagiology and hagiography converge between themselves? If holiness as a God’s gift has always points towards man, then in some regard the subject of hagiography coincides with that of hagiology. Introducing more precise distinctions, one should say that the exact meaning of "hagiography" would designate the popular biographies of saints, "scientific hagiography" would indicate the biographies of the saints, whose life has been investigated on the basis of formal criteria accepted by Congregation for the Causes of Saints. Hagiology instead would mean the realm of the knowledge, which in scientific way examines the sources and elaborates the main issues concerning holiness. It seems that more important difference can be seen in the methodology of researches themselves than in the subject of hagiography and hagiology.

The popular narration, used often by chroniclers in the biographies of the saints, should be rather replaced by more objective and scientific narration. In order to create the scientific narrations hagiologist should acquire comprehensive knowledge, which covers a large range of scientific subjects: the Bible, Tradition of the Church, hagiography, spiritual theology, liturgy, history of the Church, psychology, etc.

It is why the present paper subsequently shows the relations between hagiology and the above mentioned theological and humanistic subjects. Author is aware that the connection between hagiology and the others scientific disciplines is much wider and calls for more extensive studies. It can be said that the above paper is a small compendium in the examined subject and recognises the need to carry on further studies in this field.