The contemporary underground mining of raw minerals is more and more associated with geological and mining software packages which support the work of designers from the moment of the exploration of a deposit, determination of its size and quality, geological, hydrogeological and tectonic conditions, by planning the development and cutting of the deposit. Production planning is one of the most important activities carried out in the course of a mining project, because it allows to set specific production results of a mine in relation to a time unit, and then allows for a verification of the degree of completion of the assumed plan. At present, computer-aided design is applicable to daily or long-term output planning taking deposit, qualitative, quantitative and cost constraints into account. In the article, selected forms of ore deposits were presented. On the basis of several dozen boreholes up to 300m in length, an exemplary fragment of the ore cutting model using computer-aided design of mining works was presented. By using modern computer software - ABB MineScape with modular construction, the possibilities of improving the process of development of future exploitation areas have been determined. In particular, the arrangement of boreholes, based on which ones the cross sections were made with, present the exemplary lithostratigraphic thickness of layers, including the location of discontinuous deformations in the form of faults, and an ore bearing zone. For the block model, resources with priority for metal N o. 1 and 2 were calculated. I n the last section of the article, the cutting idea for a shallow ore deposit has been presented. The degree of effective use of the deposit has been analysed for the room and pillar mining method.
The article presents a synthetic analysis of the crude oil market in Poland. As of today, this safety is provided mainly on the basis of native lignite and hard coal resources. However, the analysis of the hard coal market conducted by the authors indicates that the carried out mining restructuring (among others) led to an excessive reduction of mining volume and employment level in the hard coal mining sector. This led to a precedent situation when Poland became an importer of this energy carrier. In addition, the European Union’s requirements for greenhouse gas emissions must be taken into account. In connection with the above, it is necessary to search for new energy sources or technologies that enable hard coal to meet the requirements. It is possible to apply the so-called clean coal technologies that allow the greenhouse gas emissions generated during coal combustion to be reduced. As of today, they are not used on a mass scale, because the use of this type of technology involves additional financial expenses. However, taking into account that technologies have been growing faster and faster, are modernized in a shorter time, making a breakthrough discovery took hundreds of years, now it is often a few months, clean coal technologies can become the optimal solution in the near future. It is also necessary to diversify the sources of obtaining imported energy carriers. The article describes coal and crude oil in terms of their mutual substitution. The article is a continuation of research conducted by the authors. Previous publications presented considerations on analogous topics related to natural gas and renewable energy sources. The crude oil market in Poland was analyzed and forecasts for oil extraction and the demand in the world and Poland by 2023 were presented. The SARIMA model was also created. The model made it possible to obtain oil an prices forecast.
This article, as far as possible based on the available literature, empirical measurements, and data from mesoscale models describes and compares expected wind conditions within the Baltic Sea area. This article refers to aspects related to the design and assessment of wind farm wind resources, based on the author’s previous experience related to onshore wind energy. The consecutive chapters of this publication are going to describe the present state and the presumptions relating to the development of wind energy within the Baltic Sea area. Subsequently, the potential of the sea was assessed using mesoscale models and empirical data from the Fino 2 mast that is located approximately 200 kilometers away from the majority of areas indicated in the Polish marine spatial development plan draft of Poland for offshore wind farm development (Maritime Office in Gdynia 2018). In the chapter describing mesoscale models, the author focused his attention on the GEOS5.12.4 model as the source of Modern-Era Retrospective Analysis for Research and Application 2 data, also known as MERRA2 (Administration National Aeronautics and Space Agency, 28), which, starting from February 2016, replaced MERRA data (Thogersen et al. 2016) and have gained a wide scope of applications in the assessment of pre-investment and operational productivity due to a remarkable level of correlation with in-situ data. Model-specific data has been obtained for eight locations, which largely overlap with the locations of the currently existing offshore wind farms within the Baltic Sea area. A significant part of this publication is going to be devoted to the description of the previously mentioned Fino 2 mast and to the analysis of data recorded until the end of 2014 by using the said mast (Federal Maritime and Hydrographic Agency 2018). The analysis has been carried out by means using scripts made in the VBA programming language, making it easier to work with large chunks of data. Measurements from the Fino 2 mast, together with long-term mesoscale model-specific measurements can be used, to some extent, for the preliminary assessment of wind farm energy yield in the areas designated for the development of renewable energy in the Polish exclusive maritime economic zone (Maritime Office in Gdynia 2018). In the final part of this article, pieces of information on the forecasted Baltic Sea wind conditions, especially within the exclusive economic zone of Poland, are going to be summarized. A major focus is going to be put on the differences between offshore and onshore wind energy sources, as well as on further aspects, which should be examined in order to optimize the offshore wind power development.
In 2015 an important part of the official evaluation of Polish scientific journals was left to experts’ judgement. In this paper we try to establish which observable factors (with available data) are closely related to the outcome of experts’ evaluation of Polish journals in economic sciences. Using the multiple regression statistical model we show that only 5 variables (out of 17) significantly explain almost 50% of the empirical variance of the experts’ evaluation. The determinants of particular interest, not entering the formal criteria and not related to the impact on global science, are: the number of citations mainly in Polish journals and the affiliation with the Polish Academy of Sciences.
“Mineral deposit model”, “deposit modelling” are the terms commonly used, although imprecise. This is often identified as the application of computerized methods to the elaboration and presentation of geological information, in particular for the mining design. Deposit modelling is the mode of presentation of deposit features, which in the meaning of the authors of such presentation, describes the deposit features between the points of observations as best as possible. Deposit modelling has a long history (XVI-XVII centuries), however such a term was not used. Varied methods of cartographic presentation of deposits and their features were proposed. The progress in the presentation of the deposit in space using isolines maps has led to the separation of methods of deposits geometrisation. Over time, a simple mathematical statistics method was used to describe the deposit parameters, followed by geostatistical methods. Some of them were however not commonly used as too troublesome. The computer based approach to the presentation of geological data has an unquestionable value but is accompanied by the possibility of inappropriate formalized and erroneous interpretations and a presentation as to whether the basic rules of geological knowledge were neglected. Deposits modeling is a conceptual task and cannot be fully automated.
The paper focuses on the modelling of bromate formation. An axial dispersion model was proposed to integrate the non-ideal mixing, mass-transfer and a kinetic model that links ozone decomposition reactions fromthe Tomiyasu, Fukutomi and Gordon (TFG) ozone decaymodelwith direct and indirect bromide oxidation reactions, oxidation of natural organicmatter and its reactionswith aqueous bromine. To elucidate the role of ammonia an additional set of reactions leading to bromamine formation, oxidation and disproportionation was incorporated in the kinetic model. Sensitivity analysis was conducted to obtain information on reliability of the reaction rate constants used and to simplify the model.
Four Geodynamical Expeditions of the Polish Academy of Sciences carried through wide research seismic program in West Antarctica in 1979-1991. Three of these expeditions operated in the Bransfield Strait. The experiment of deep refraction and wide-angle reflection in West Antarctica focused on deep structure of the lithosphere, mainly of the Earth's crust. The network of deep seismic soundings (DSS) profiles covered all the Bransfield Strait. Five land stations on the South Shetland Islands, three stations on the Antarctic Peninsula and nine ocean bottom seismographs (OBS) recorded seismic waves, generated by explosions in a sea. The Bransfield Rift and the Bransfield Platform form a marginal basin against a volcanic arc of the South Shetland Islands. The paper presents new results of 2-D seismic modeling for network of five selected profiles. Four of them, ranging in lenght from 150 to 190 km, crossed main structures of the Bransfield Strait and the fifth, which connected the other ones and was 310 km long, ran along the Bransfield Rift. Two or three seismic models were presented for each profile. Finally, mutually corrected and controlled 2-D models of described profiles were constructed. They all presented spatial complex structure of the Earth's crust in a young rift of the Bransfield Strait, including extent of its main element i.e. anomalous high velocity body (HVB) (Vp > 7.4 km/s), detected in 10-30 km depth range except profile DSS-4 (southwest part of the Bransfield Strait). This inhomogeneity is interpreted as intrusion of the upper mantle (?asthenosphere) during stretching of the continental crust. The Moho discontinuity was found at depth 30-35 km, with velocities equal to about 8.1 km/s.
The analysis of changes in the mechanical properties of wooden mining cribs under the influence of different types of exploitation loads is the question for which deals with many domestic and abroad research centers deal with. High The high interest in this subject results from the increase of the conducted depth exploitation, which contributes to the increase in both the vertical pres-sure and the complexity of geological – mining conditions and in- the intensification of natural hazards. Another reason is the tendency of decreasing the thickness of the exploited ores deposits. Wooden crib support is used Both both in underground ore, hard coal and salt mining is used wooden crib support. Mining cribs with various configurations are especially useful for the reinforcement of excavations workings behind the front and for further strengthen of the crossings. In particular, additional reinforcement support in the form of wooden cribs (pile supporting), which shall be left empty or filled with waste rock is applied in the ore mining in places where found extended rooms or drifts are found or in places with degraded roof conditions, applies additional reinforcement support in the form of wooden cribs (pile supporting), which shall be left empty or filled with waste rock. During underground ex-ploitation is produced waste Waste rock, which comes from the access, prepar-atory excavations and from ongoing field of exploitation is produced during underground exploitation. In the case of the underground exploitation of cop-per ore, waste rock is used to fill voids after exploitation as rock stowing. It is also used for filling mining wooden cribs, as an artificial support and for harder transportation roads. This paper presents the results of the laboratory strength tests performed on models of four-point timber cribs, built with beams set horizontally, at the ge-ometrical scale of 1:10. In the laboratory research Research wooden cribs models with size 200 × 200 × 200 mm and 100 × 100 × 100 mm were used in the laboratory. The paper describes the maximum loading capacity of the cribs consisted consisting only of beams and filled with waste rocks. In addition, a vertical and appropriate strain of cribs at maximum force was shown. On the basis of laboratory research it was found that the use of the same number of timbers and the management of waste rocks, the filling of the four-point cribs with the waste rocks allowed several times to increase its support to be increased several times.
The author analyses onymic practices of Poznań–based craftsmen forming guilds. In the names of the inhabitants of Poznań, which stabilised until the end of the 18th century, she seeks traces of the so-called cognomens, i.e. secondary personal designations granted to apprentices who were becoming masters. The names resulted from community acts of creation, which were of ludic nature. Referring to German onymic practices and pointing to the so-called Schleifnamen, the author discusses specific codes of European middle-class culture. She focuses on the transfer of models and patterns to Polish urban communities.
Philip Sabin points out that modern wargames not only contain substantial amounts of historical information but also arrange it into interactive models which depict historical processes in a simplified manner. Such models can be used in historical research as well, complementing the discourse through more holistic and mathematically strict accounts, and providing tools that impose some discipline on counter- factual speculation.
Given a linear discrete system with initial state x0 and output function yi , we investigate a low dimensional linear systemthat produces, with a tolerance index ǫ, the same output function when the initial state belongs to a specified set, called ǫ-admissible set, that we characterize by a finite number of inequalities. We also give an algorithm which allows us to determine an ǫ-admissible set.
Validation results of a theoretical model that describes the formation of bromate during ozonation of bromide-containing natural waters are presented. An axial dispersion model integrating the nonideal mixing, mass-transfer and a kinetic model that links ozone decomposition reactions from the Tomiyasu, Fukutomi and Gordon ozone decay model with direct and indirect bromide oxidation reactions, oxidation of natural organicmatter and reactions of dissolved organics and aqueous bromine was verified. Themodel was successfully validated with results obtained both at a laboratory and a full scale. Its applicability to different water supply systems was approved.
The paper presents modeling and simulation results of the operation of a three-phase fluidized bed bioreactorwith partial recirculation of biomass. The proposed quantitative description of the bioreactor takes into account biomass growth on inert carriers, microorganisms decay and interphase biomass transfer. Stationary characteristics of the bioreactor and local stability of steady-stateswere determined. The influence of microbiological growth kinetics on the multiplicity of steady-states was discussed. The relationship between biofilm growth and boundaries of fluidized bed existence was shown.
The article discusses changes in Polish regulations concerning assessment of the climate hazard in underground mines. Currently, the main empirical index representing the heat strain, used in qualification of the workplace to one of the climate hazard levels in Poland is the equivalent climate temperature. This simple heat index allows easy and quick assessment of the climate hazard. To a major extent, simple heat indices have simplifications and are developed for a specific working environments. Currently, the best methods used in evaluation of microclimate conditions in the workplace are those based on the theory of human thermal balance, where the physiological parameters characterising heat strain are body water loss and internal core temperature of the human body. The article describes the results of research on usage of equivalent climate temperature to heat strain evaluation in underground mining excavations. For this purpose, the numerical model of heat exchange between man and his environment was used, taken from PN-EN ISO 7933:2005. The research discussed in this paper has been carried out considering working conditions and clothing insulation in use in underground mines. The analyses performed in the study allowed formulation of conclusions concerning application of the equivalent climate temperature as a criterion of assessment of climate hazards in underground mines.
The article highlights the issues of the quality of the newly developed residential areas in Stockholm, in the times of one of the most development intense times in the history of the city. The city of Stockholm has a population of ca. one million residents today and is one of the fastest growing cities in Europe. The high increase in population numbers, high birth rate and strong economy have been the main factors contributing to the rapid city growth. The urgent need for new houses has been addressed by Stockholm’s politicians with an ambitious housing programme. The housing shortage together with the city´s booming economy and actively applied planning policies have created challenges for the decision makers and for the city planners. Most of Stockholm´s new residential areas are being planned outside the city centre which requires a revised approach to the character of the planned spaces and to their density. However, the issues of the quality of the currently planned and built areas are being raised more and more often. Not only the architectural quality has been discussed, but also the scale, structure typologies, the quality of the functional and spatial programmes and that of public spaces. A planning model that has been applied in Stockholm for several years is based on a close co-operation between the city´s planning administration bodies and private investors. A critical element of this kind of a planning model is a strong vision for the city´s future development. The city’s planning administration bodies assure an applicable guidance throughout the planning process. Analysis and conclusions presented in the article are based on practice at planning and administration bodies in Stockholm and in the region of Stockholm in the years 2005-2018.
Control of the technological processes of coal enrichment takes place in the presence of wide disturbances. Thus, one of the basic tasks of the coal enrichment process control systems is the stabilization of coal quality parameters at a preset level. An important problem is the choice of the controller which is robust for a variety of disturbances. The tuning of the controller parameters is no less important in the control process . Many methods of tuning the controller use the dynamic characteristics of the controlled process (dynamic model of the controlled object). Based on many studies it was found that the dynamics of many processes of coal enrichment can be represented by a dynamic model with properties of the inertial element with a time delay. The identification of object parameters (including the time constant) in industrial conditions is usually performed during normal operation (with the influence of disturbances) from this reason, determined parameters of the dynamic model may differ from the parameters of the actual process. The control system with controller parameters tuned on the basis of such a model may not satisfy the assumed control quality requirements. In the paper, the analysis of the influence of changes in object model parameters in the course of the controlled value has been carried out. Research on the controller settings calculated according to parameters T and τ were carried out on objects with other parameter values. In the studies, a sensitivity analysis method was used. The sensitivity analysis for the three methods of tuning the PI controller for the coal enrichment processes control systems characterized by dynamic properties of the inertial element with time delay has been presented. Considerations are performed at various parameters of the object on the basis of the response of the control system for a constant value of set point. The assessment of considered tuning methods based on selected indices of control quality have been implemented.
The presence of lipopolysaccharide (LPS) in blood induces an inflammatory response which leads to multiple organ dysfunction and numerous metabolic disorders. Uncontrolled, improper or late intervention may lead to tissue hypoxia, anaerobic glycolysis and a disturbance in the acid -base balance. The effects of LPS-induced toxemia on biological and immunological markers were well studied. However, parameters such as base excess, ions, and acid-base balance were not fully investigated. Therefore, the objective of this study was to examine these blood parameters collectively in LPS-induced inflammatory toxemia in rat’s model. After induction of toxemia by injecting LPS at a rate of 5 mg/kg body weight intravenously, blood was collected from the tail vein of twenty rats and immediately analyzed. After 24 hours, the animals were sacrificed and the blood was collected from the caudal vena cava. The results revealed that the levels of pH, bicarbonate, partial pressure of oxygen, oxygen saturation, Alveolar oxygen, hemoglobin, hematocrit, magnesium (Mg2+), and calcium (Ca2+) were significantly decreased. On the other side, the levels of Base excess blood, Base excess extracellular fluid, partial pressure of carbon dioxide, lactate, Ca2+/Mg2+, potassium, and chloride were significantly increased compared to those found pre toxemia induction. However, sodium level showed no significant change. In conclusion, Acute LPS-toxemia model disturbs acid-base balance, blood gases, and ions. These parameters can be used to monitor human and animal toxemic inflammatory response induced by bacterial LPS conditions to assist in the management of the diagnosed cases.
The operational mineral deposit reconnaissance tends to evaluate its parameters to conduct safe and profitable production. Particular deposit parameters, important from the point of mineral deposit management, are estimated on the basis of observations carried out by mining geological surveys. These observations usually involve sampling, drilling, laboratory analyses and others. The use of fuzzy description to assess the parameters of the mineral deposit was proposed in the paper. In the fuzzy characteristics, an imprecise descriptive description appeared in place of a particular numerical quantity. This approach was used to description of the ore deposit features (metal content, volume, and metal yield) by assigning them specific characteristic functions, whose distributions were based on basic statistical quantities. Characteristic functions can be used to prepare operational strategies for any configuration of required deposit parameters resulting from the production management needs. For this purpose, selected logical operators of fuzzy sets were used. In the next approach to fuzzy modeling, an opportunity to characterize the deposit in a subjective approach was indicated, where the assessment of the deposit parameters is based on rough, in some way, discretionary observation and evaluation. Such model construction enabled the overall assessment of the deposit from the point of view of any parameters. Through the implementation of appropriate inference rules, adequate fuzzy control planes were obtained, which may also be useful in the context of operational mine strategy planning.
This article considers designing of a renewable electrical power generation system for self-contained homes away from conventional grids. A model based on a technique for the analysis and evaluation of two solar and wind energy sources, electrochemical storage and charging of a housing area is introduced into a simulation and calculation program that aims to decide, based on the optimized results, on electrical energy production system coupled or separated from the two sources mentioned above that must be able to ensure a continuous energy balance at any time of the day. Such system is the most cost-effective among the systems found. The wind system adopted in the study is of the low starting speed that meets the criteria of low winds in the selected region under study unlike the adequate solar resource, which will lead to an examination of its feasibility and profitability to compensate for the inactivity of photovoltaic panels in periods of no sunlight. That is a system with fewer photovoltaic panels and storage batteries whereby these should return a full day of autonomy. Two configurations are selected and discussed. The first is composed of photovoltaic panels and storage batteries and the other includes the addition of a wind system in combination with the photovoltaic system with storage but at a higher investment cost than the first. Consequently, this result proves that is preferable to opt for a purely photovoltaic system supported by the storage in this type of site and invalidates the interest of adding micro wind turbines adapted to sites with low wind resources.
This paper demonstrates that if a linear dependence of arc dissipated power on power supplied is introduced at an initial stage of analysis, then, with some simplifying assumptions, the classical Mayr model is obtained. Similarly, if this dependence is taken into account in a model with residual conductance, the modified Mayr model is obtained. The study takes into consideration the local phenomenon of sudden voltage drop accompanying linear current decrease occurring in the circuit breaker. To account for this phenomenon, the Dirac delta function and its approximation by a Gaussian function, representing power or enthalpy disturbances, are introduced to the power balance equation. It is demonstrated that both variants yield the same effect, leading to identical differential equations. Macromodels of the circuit-breaker arc are created and connected with the power source circuit with lin- early decreasing current. The results obtained were found to be consistent with experimental data available in the literature. The models presented are based on a fairly uncomplicated 1st order differential equation and offer a straightforward physical interpretation of the phenomena in question.
An algorithm of determination of mechanical stresses and deformations of the magnetic circuit shape, caused by forces of magnetic origin, is presented in this paper. The mechanical stresses cause changes of magnetizing characteristics of the magnetic circuit. The mutual coupling of magnetic and mechanical fields was taken into account in the algorithm worked out. A computational experiment showed that it was possible to include the interaction of both fields into one numerical model. The elaborated algorithm, taking into account the impact of mechanical stresses on magnetic parameters of construction materials, can be used in both the 2D and the 3D type field-model.
The quantitative description of an airlift bioreactor, in which aerobic biodegradation limited by carbonaceous substrate and oxygen dissolved in a liquid takes place, is presented. This process is described by the double-substrate kinetics. Mathematical models based on the assumption of plug flow and dispersion flow of liquid through the riser and the downcomer in the reactor were proposed. Calculations were performed for two representative hydrodynamic regimes of reactor operation, i.e. with the presence of gas bubbles only within the riser and for complete gas circulation. The analysis aimed at how the choice of a mathematical model of the process would enable detecting the theoretical occurrence of oxygen deficiency in the airlift reactor. It was demonstrated that the simplification of numerical calculations by assuming the “plug flow” model instead of dispersion with high Péclet numbers posed a risk of improper evaluation of the presence of oxygen deficiency zones. Conclusions related to apparatusmodelling and process design were drawn on the basis of the results obtained. The paper is a continuation of an earlier publication (Grzywacz, 2012a) where an analysis of single-substrate models of the airlift reactor was presented.
Introduction: Platelet-rich plasma (PRP) preparations can be used in bone tissue healing but there are numerous doubts among clinical orthopedists about effectiveness of this method. Materials and methods: The studies were carried out in 12 rabbits of white termond breed. In operating room we operationally generated cylindrical, unicortical defects of the diameter of 4 mm in the middle of the shafts of both femurs. The defects in the left bones were left without filling and served as controls, and 0.7 ml of the ready-to-use PRP was administered to the defects in the right bones (experimental group). We evaluated the usefulness of the diagnostic methods applied: biomechanical tests, micro-CT tests, densitometry, typical radiology, macroscopic measurements, histopathological examinations. Results: The macroscopic measurements showed a statistically significant increase in the dimension in the area of the right defect filled with PRP in relation to the control group. In experimented group, the assessment of the X-ray images showed the formation of a callus cuff around the defects. Densitometric examinations showed no statistically significant differences between defects in the experimental and control group. The analysis of the micro-CT examina- tions showed an increase in the total volume of the tissue examined (Vb) and the low density tissue fraction (Vb2) in the experimental group. The biomechanical examinations revealed signi- ficant decrease in the maximum breaking force (F max) necessary to break the bone in the experi- mental group in relation to the control group. Conclusions: Platelet-rich plasma (PRP) stimulates bone formation in the area of bone defects and may accelerate bone regeneration.
This paper presents a complex study of anhydrite interbeds influence on the cavern stability in the Mechelinki salt deposit. The impact of interbeds on the cavern shape and the stress concentrations were also considered. The stability analysis was based on the 3D numerical modelling. Numerical simulations were performed with use of the Finite Difference Method (FDM) and the FLAC3D v. 6.00 software. The numerical model in a cuboidal shape and the following dimensions: length 1400, width 1400, height 1400 m, comprised the part of the Mechelinki salt deposit. Three (K-6, K-8, K-9) caverns were projected inside this model. The mesh of the numerical model contained about 15 million tetrahedral elements. The occurrence of anhydrite interbeds within the rock salt beds had contributed to the reduction in a diameter and irregular shape of the analysed caverns. The results of the 3D numerical modelling had indicated that the contact area between the rock salt beds and the anhydrite interbeds is likely to the occurrence of displacements. Irregularities in a shape of the analysed caverns are prone to the stress concentration. However, the stability of the analysed caverns are not expected to be affected in the assumed operation conditions and time period (9.5 years).
Rock excavation is a basic technological operation during tunnelling and drilling roadways in underground mines. Tunnels and roadways in underground mines are driven into a rock mass, which in the particular case of sedimentary rocks, often have a layered structure and complicated tectonics. For this reason, rock strata often have highly differentiated mechanical properties, diverse deposition patterns and varied thicknesses in the cross sections of such headings. In the field of roadheader technology applied to drilling headings, the structure of a rock mass is highly relevant when selecting the appropriate cutting method for the heading face. Decidedly differentiated values of the parameters which describe the mechanical properties of a particular rock layer deposited in the cross section of the drilled tunnel heading will influence the value and character of the load on the cutting system, generated by the cutting process, power demand, efficiency and energy consumption of the cutting process. The article presents a mathematical modelling process for cutting a layered structure rock mass with the transverse head of a boom-type roadheader. The assumption was made that the rock mass being cut consists of a certain number of rock layers with predefined mechanical properties, a specific thickness and deposition pattern. The mathematical model created was executed through a computer programme. It was used for analysing the impact deposition patterns of rock layers with varied mechanical properties, have on the amount of cutting power consumed and load placed on a roadheader cutting system. The article presents an example of the results attained from computer simulations. They indicate that variations in the properties of the rock cut – as cutting heads are moving along the surface of the heading face – may have, apart from multiple other factors, a significant impact on the value of the power consumed by the cutting process.