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Number of results: 35
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Abstract

The evaluation of threats connected with the presence of methane in coal seams is based on our

knowledge of the total content of this gas in coal. The most important parameter determining the potential

of coal seams to accumulate methane is the sorption capacity of coal a. It is heavily influenced by the

degree of coalification of the coal substance, determined by the vitrinite reflectance R0 or the content of

volatile matter V daf. The relationship between the degree of coalification and the sorption capacity in the

area of the Upper Silesian Coal Basin (USCB) has not been thoroughly investigated, which is due to the

zonation of methane accumulation in this area and the considerable changeability of methane content in

various localities of the Basin. Understanding this relationship call for in-depth investigation, especially

since it depends on the analyzed reflectance range. The present work attempts to explain the reasons for

which the sorption capacity changes along with the degree of coalification in the area of Jastrzębie (the

Zofiówka Monocline). The relationship between parameters R0 and V daf was investigated. The authors

also analyzed changes of the maceral composition, real density and the micropore volume. Furthermore,

coalification-dependent changes in the sorption capacity of the investigated coal seams were identified.

The conducted analyses have indicated a significant role of petrographic factors in relation to the accumulation

properties of the seams located in the investigated area of USCB.

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Authors and Affiliations

Katarzyna Godyń
Barbara Dutka
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Abstract

The subject of the study was the No. 116/2 coal seam belonging to the Cracow Sandstone Series of the Upper Silesian Coal Basin. Reflectograms of the samples taking into account all the vitrinite group macerals present in the coal were recorded for Δ Ro close to the standard deviation and in the standard range. A careful analysis of vitrinite reflectograms reveals the presence of three or four clearly distinguished peaks. When assessing the rank of coal, only the main maximum, peak No. 4, was considered to be significant. Measurements of the average reflectance of collotelinite were made only on the vitrinite surfaces with a thickness of more than 1 mm. Only two maxima were revealed on detailed reflectograms. These maxima correlate with the peaks marked as No. 3 and 4 in the sample reflectograms taking into account all the vitrinite group macerals. The C daf content in the tested coal from the Janina coal mine is between 75.9 and 77.5 wt%, while for vitrain, it ranges from 71.1 to 75.5 wt%. This relationship is an exponential regression with a correlation coefficient of r = 0.95h and can be approximated by a linear correlation of r = 0.94. The correlation strength between the volatile matter content and the coefficient of average reflectance in the vitrinite of the tested coal was also examined. The statistically significant correlation is strong, which is expressed by the exponential correlation coefficient “r” being close to 0.99 and its linear approximation with the correlation coefficient r = 0.98. However, no correlation was found between the measured reflectance values and the GI coefficient calculated for the examined samples.
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Authors and Affiliations

Jacek Misiak
1
ORCID: ORCID

  1. AGH University of Kraków, Faculty of Geology, Geophysics and Environment Protection, Poland
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Abstract

The paper deals with analysis of recognition of surface quality with reflective structures. Such surfaces are common in metallic materials cut using a saw or polished. There are no easy methods to identify such elements after machining. This issue is crucial in the industry for quality control as recognition of the elements, for instance after failure, allows for a detailed study of their manufacturing process. Firstly, six cuboid steel elements were obtained from a larger beam with a circular saw. Then, the bidirectional reflection distribution function (BRDF) was obtained for each element 3 times. The BRDF profiles were used in custom recognition software based on the K-nearest neighbors algorithm. In total, 140 variants of the classifier were tested and analyzed. Additionally, each variant was solved 200 times with different splits of the dataset. The results showed a high multiclass accuracy in all considered variants of the algorithm, with multiple variants achieving 100% accuracy. This level of performance was attained with only 1 to 2 training samples per class. Its low numerical complexity, easy experimental procedure, and “one-shot” nature allow for fast recognition, which is crucial in industrial applications.
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Authors and Affiliations

Adam Ciszkiewicz
1
Janusz Jaglarz
2
Tadeusz Uhl
3

  1. Faculty of Mechanical Engineering, Cracow University of Technology, Al. Jana Pawła II 37, 31-864 Cracow, Poland
  2. Faculty of Material Engineering, Cracow University of Technology, Al. Jana Pawła II 37, 31-864 Cracow, Poland
  3. Department of Robotics and Mechatronics, Faculty of Mechanical Engineering and Robotics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Cracow, Poland
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Abstract

The author, as a former pupil of the title figure of this paper, and as a leading his cooperator in numerous creative works, recalls memoires and presents an analysis of the personality of late professor of architectute, J. Tadeusz Gawłowski. The paper represents both – objective and official features of chronicle, hence also introduces readers into more personal secrets of the outstanding architect: creator, scholar and academic teacher – being simultaneously a picturesque and friendly person. He was connected mainly with Kraków University of Technology, but sharing also his activity in order to fulfill needs of three other, important academic schools.

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Authors and Affiliations

Maciej Złowodzki
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Abstract

The present article investigates theoretically the refection and transmission through a lossless dielectric slab embedded between two semi−infinite left−handed materials (LHMs) in which the electric permittivity and magnetic permeability are simultaneously negative. The LHM is assumed to be dispersive according to Lorentz as well as Drude medium model. The reflection and transmission coefficients are studied with the angle of incidence, frequency and slab thickness. The effect of the damping frequency is also investigated. It is found that the damping frequency has an insignificant effect on reflected, transmitted and loss powers. Band pass filter is one of the possible applications of the proposed structure.

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Authors and Affiliations

S.A. Taya
D.M. El-Amassi
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Abstract

The article represents research into poetry written during the Revolution of Dignity (2014). Such artistic texts are analyzed as a kind of phenomenon of contemporary literature. These are the poems of famous authors or even amateurs, united by a common sacred code. They appeal to the patterns and archetypes of the collective consciousness of Ukrainians. In the poetry of Euromaidan the researcher underlines two types of sacralization, which can be conditionally called masculine and feminine (paternal and maternal). The masculine type of this process realizes a symbolic projection of the figure of Jesus Christ. This symbol emphasizes the determination of the act, active attitude, the idea of fighting for the truth, as well as the willingness to sacrifice their own lives for the common good. The feminine version of the proces of sacralization is the Virgin Mary. This image appeals not to the heroic act, but to its emotional reflection, more specifically – the suffering, pain, traumatic experience of the victim. It corresponds to the archetypal image of the Mother of God, the Suffering Mother, who sacrifices her own son to death and cries for him later. The embodiment of the Christian sacrum in the poetry of the Maidan testifies to the fidelity to both European and Ukrainian traditions.
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Authors and Affiliations

Jarosław Poliszczuk
1
ORCID: ORCID

  1. Uniwersytet im. Adama Mickiewicza w Poznaniu
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Abstract

We report on the absorption properties of polarization-insensitive transmissive and reflective metamaterial absorbers based on two planar aluminium periodic structures and SU-8 epoxy resist. These absorbers were investigated using numerical simulation and experimental methods in the terahertz range (below 2 THz). SU-8 is a very promising organic material for dielectric layers in planar metamaterials, because its application simplifies the process of fabricating these structures and significantly reduces the fabrication time. The experimental absorption of the metamaterial absorbers has narrowband characteristics that were consistent with the numerical simulations. Power flow analysis in the transmissive metamaterial unit cell shows that the absorption in the terahertz range occurs primarily in the SU-8 layer of the absorber.

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Authors and Affiliations

B. Grześkiewicz
A. Sierakowski
J. Marczewski
N. Pałka
E. Wolarz
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Abstract

Studies on the quality of bituminous coal are mainly focused on physico-chemical analysis, examining the ash content, sulphur content, volatile matter content, moisture content, and the Net Calorific Value of coal. Until now, the above mentioned parameters form the basis of the Polish Standard PN-82/87002, on the basis of which individual types of bituminous coal are determined. In addition, an elemental analysis, providing information about the content of primary elements in the organic matter of solids, i.e. coal, hydrogen, nitrogen, oxygen, and sulphur, is carried out for the selected samples. This issue has been studied by many authors, which undoubtedly provide invaluable knowledge due to the huge amount of data, but, as the authors themselves indicate, the knowledge of the petrography of coal, coking properties (Probierz et al. 2012) and finally the coke obtained from individual coal types (based on tests carried out using the Karbotest installation or the so-called „box tests” performed in the coke oven battery) is still very limited. The article discusses the impact of petrographic composition on the quality of metallurgical coke. The analysis was performed using samples of coking coal from the following mines: Pniówek, Zofiówka, Borynia, and Krupiński. The mentioned coal types are used to produce coke mixtures used for the production of coke in the Przyjaźń and Radlin coking plants. Based on the rank of coal and physicochemical parameters, the mentioned coal types were classified according to the Polish classification and the UN/ECE International Classification of In-Seam Coals (UN/ECE 1995). The prediction of thermomechanical properties of coke (CSR and CRI) performed according to the original CCP method were compared with the results obtained using the classical method of Nippon Steel Corporation.

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Authors and Affiliations

Iwona Jelonek
Zbigniew Jelonek
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Abstract

Being reflective is one of the most paramount features that EFL (English as a Foreign Language) teachers need to be equipped with in the post-method era for their professional growth and development. The present study aimed to explore reflective teaching from a multi-dimensional perspective in terms of a) determinants that simulates teachers to reflect, b) consequences that teachers experience as a result of their reflective teaching, and c) obstacles that may arise and preclude teachers from reflective teaching. Qualitative data collection method was employed to gather data from 10 EFL teachers triangulating semi-structured interviews, diaries, journal, and observation. Data analysis via MAXQDA led to the emergence of three models for each dimension of the study. The results revealed that teachers not only reflect to respond to a problem, but also they reflect to diminish some negative factors like stress or anxiety on the part of both learners and themselves as well as improving, enhancing, or mending something in teaching or learning. The codes of determinants were also conceptualized into three broad categories of reflection-in-action, reflection-on-action, and reflection-for-action with the reflection-for-action used more frequently by the teachers. In the case of consequences, the codes were classified into two categories of internal and external consequences. It was also concluded that some of the consequences reinforce the reflective teaching and play the role of determinants motivating teachers to reflect again. Regarding the obstacles, after categorizing the codes into external and internal obstacles, it was observed that external factors are more robust.

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Authors and Affiliations

Farzaneh Tabassi
Afsaneh Ghanizadeh
Parinaz Gharooni Beigi
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Abstract

The reflection coefficient of the open end belongs among the essential parameters in the physical description of a flue organ pipe. It leads directly to practical topics such as the pipe scaling. In this article, sound propagation is investigated inside an organ pipe with the most intense mean flow that is achievable under musically relevant conditions. A theoretical model is tested against the experimental data to obtain a suitable formula for the reflection coefficient when a non-negligible flow through the open end is considered. The velocity profile is examined by means of particle image velocimetry. A fully developed turbulent profile is found and interactions of the acoustic boundary layer with the turbulent internal flow are discussed. A higher value of the end correction than expected from the classical result of Levine and Schwinger is found, but this feature shall be associated with the pipe wall thickness rather than the mean flow effects.
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Bibliography

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Authors and Affiliations

Viktor Hruška
1
Pavel Dlask
1

  1. Academy of Performing Arts in Prague, Musical Acoustics Research Centre, Prague, Czech Republic
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Abstract

This paper presents a simulation study of the simultaneous reconstruction of the non-smooth strain distribution of an optical fiber Bragg grating and its temperature, which is based on the reflection spectrum of the reflected beam of the grating. The transition matrix method was used to model the reflection spectrum of the grating, and the nonlinear Nelder- Mead optimization method was used to simultaneously reconstruct the strain distribution along the grating and its temperature. The results of simulations of simultaneous reconstruction of the strain profile and temperature indicate good accord with the strain profiles and temperature set. The reconstruction errors of the strain profiles are less than 1.2 percent and the temperature change errors are less than 0.2 percent, with a noise level of 5 percent.
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Authors and Affiliations

Małgorzata Detka
1
Cezary Kaczmarek
2

  1. Faculty of Electrical Engineering, Automatic Control and Computer Science, Kielce University of Technology, Poland
  2. Faculty of Electrical Engineering and ComputerScience, Lublin University of Technology, Poland
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Abstract

The author of the article analyzes the first literary attempts to reflect the experience of Russia’s full‑scale war against Ukraine. The main attention is paid to the problem of the traumatic experience of the war, based on the first feelings of shock and its consequences. The researcher considers three books (anthologies of poems, essays and diaries Poetry without Shelter, The War‑2022 and Oksana Zabuzhko’s essay A Long Journey), which were published during the first year of the war. These are dissimilar books, but they represent one problem from different points of view. The texts are those of contemporary Ukrainian authors who survived the traumatic experience of the Russian invasion in February 2022 in different places and under different circumstances. The author of the article interprets these works as a cultural tool in the process of mastering the state of shock, and later – as a mechanism for the verbal representation of the trauma itself.
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Bibliography

Butler J., Freymy viyny. Chyyi zhyttya oplakuyut'?, per. z anhl. Yu. Kravchuk, Kyyiv 2016.
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Matusiak A., Wyjść z milczenia. Dekolonialne zmagania kultury i literatury ukraińskiej XXI wieku z traumą posttotalitarną, Wojnowice – Wrocław 2020.
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Authors and Affiliations

Oksana Pukhonska
1

  1. The National University of Ostroh Academy
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Abstract

The main paradox of the book by Oleg Sentsov, the famous Ukrainian filmmaker, is that despite its distinctly documentary basis the text is endowed with obvious qualities of fictionalization. In this regard, the purpose of the article is to identify the fictional firsts in Oleg Sentsov’s book “The chronicle of one hunger strike”, based on cultural, historical, biographical, and hermeneutical methods, and also to analyze these firsts in terms of how they shape the idea and artistic content of this work. As a result, the conclusions were formulated according to which the book under consideration uses various forms of fictionalization of comments, reflections, dreams, memories, and even physiological processes of the human body to fictionalize the diary space through which a real person acquires an artistic dimension, which paradoxically does not undermine their authenticity, but, on the contrary, gives the real person fictional conviction and powerful emotional power and depth.
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Authors and Affiliations

Feliks Shteinbuk
1

  1. Univerzita Komenského v Bratislave
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Abstract

The given article explores the topic of the content and poetic specificity of Ukrainian Christmas carols published in Pochayiv Bohohlasnyk (1790/1791), the republication of which was carried out thanks to the Ukrainian scholar Yuriy Medvedyk. Ivan Franko’s ideas as to the context of Ukrainian carols from Bohohlasnyk seem rather important. The author of the paper believes that I. Franko was right in his recommendations “to look for mixtures of the influences of western and eastern traditions” in the texts of such works, paying special attention to the Polish impact. The given article also deals with the division of these Christmas songs into the naïve and the reflection related, as well as scholars’ analysis of the language of these carols (that was mainly one of the reasons why carols were popular among ordinary people). One can vividly see that Christmas carols are based on a national component that can be traced from “transferring the Bethlehem scenario into Ukraine and its rural world of customs, circumstances, feelings and communication” (Mykhaylo Vozniak). Consequently, the carols have acquired a high literary value. As proof, t certain carols appeared in the folklore collections of Volodymyr Hnatyuk, Pavlo Chubynskyy and Klyment Kvitka, as well as present day editions of Christmas carols, Epiphany songs and literary works. The given paper also includes crucial folklore records of Christmas carols from Pochayiv Bohohlasnyk compiled by students of the Ivan Franko National University in Lviv.
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Authors and Affiliations

Василь Івашків
1
ORCID: ORCID

  1. Львівський національний університет імені Івана Франка
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Abstract

This work concerns the study of the coatings for the ultrasound frequency range as a quasi one-dimensional phononic crystal structure protecting a sea object against high resolution active sonar in the frequency range most commonly found for this type of equipment. The topology of the examined structure was optimized to obtain a band gap in the 2.2-2.3 MHz frequency band. For this purpose, a genetic algorithm was used, which allows for optimal distribution of individual elements of the ultrasound multilayer composite. By optimal distribution is meant to achieve a structure that will allow minimal reflectance in a given frequency range without height reflectance peaks with a small half width. Analysis of the wave propagation was made using the Transfer Matrix Method (TMM). As part of the research, 15 and 20-layer structures with reflectance at the level of 0.23% and 0.18%, respectively, were obtained. Increasing the number of layers in the analyzed structures resulted in finding such a distribution in which a narrow band of low reflectance was obtained, such distributions could also be used as bandpass filters. The use of a genetic algorithm for designing allows to obtain modern coatings, the characteristics of which result from the structure.
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Authors and Affiliations

S. Garus
1
ORCID: ORCID
W. Sochacki
1
ORCID: ORCID
J. Garus
1
ORCID: ORCID
A.V. Sandu
2
ORCID: ORCID

  1. Czestochowa University of Technology, Department of Mechanics and Fundamentals of Machinery Design, Faculty of Mechanical Engineering and Computer Science, 73 Dąbrowskiego Str., 42-201 Częstochowa, Poland
  2. Gheorghe Asachi Technical University of Iasi, Faculty of Materials Science and Engineering, Blv d. D. Mangeron 71, 700050 lasi, Romania
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Abstract

Solar radiation reflectance was analysed to characterize Arctic ornithogenic tundra developing in the vicinity of large breeding colony of Brunnich‘s guillemots Uria lomvia and kittiwakes Rissa tridactyla at the foot of Gnĺlberget cliff (Hornsund, SW Spitsbergen). Radiometric method was found to be a useful tool for studying structure and functioning of plant formations. We measured reflectance of four wavelengths: 554 nm (YG), 655 nm (RED), 870 nm (NIR) and 1650 nm (SWIR) at 10 plots situated along the transect running from the colony to the sea. Moreover, data of plant community character, species quantitative composition as well as total biomass were collected to relate these parameters with the spectral values. The results showed that radiometric data characterized vegetation well enough to recognize the same plant communities on the basis of spectral reflectance as distinguished with traditional phytosociological methods.

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Authors and Affiliations

Katarzyna Zmudczyńska
Adrian Zwolicki
Mateusz Barcikowski
Adam Barcikowski
Lech Stempniewicz
ORCID: ORCID
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Abstract

In this study a metal clad waveguide sensor with a metamaterial guiding layer is analyzed. Sensitivity of the proposed sensor is derived using dispersion and Fresenal’s equations for waveguiding mode and reflection mode. While efficiently analyzing and comparing the results with the existing one, some interesting findings are achieved. It is observed that the proposed sensor shows larger cover layer sensitivity and larger adlayer sensitivity compared to the dielectric guiding layer sensor due to adsorbtive properties of metamaterial. Henceforth, it concludes that the proposed sensor shows sensitivity improvement over a dielectric guiding layer sensor.

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Authors and Affiliations

A. Upadhyay
Y.K. Prajapati
R. Tripathi
V. Singh
J.P. Saini
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Abstract

Results of the studies of optical properties of anti-reflective glasses with various texturization patterns, which were used as a coating for crystalline silicon solar cells, are presented. It was found that glass samples sorted by their optical transmittance demonstrated the same order as when sorted by their solar-cell short-circuit current enhancement parameter. The value of the latter depended on the parameters of texturization, such as the surface density of inclusions and their profile, and the depth of etching pits. A 2% relative increase of the solar cell efficiency was obtained for the best glass sample for null degree angle of incidence, proving enhanced light trapping properties of the studied glass.

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Authors and Affiliations

M. Pociask-Bialy
K.D. Mynbaev
M. Kaczmarzyk
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Abstract

The aim of this study was to identify thoroughly the geological structure of the Choszczno Anticline for potential CO2 storage. The paper presents the interpretation of seismic materials for a selected seismic profile reprocessed into a section of reflection coefficients characterized by increased recording resolution as compared to the wave image. Particular attention was paid to the geological complexes associated with the Jurassic reservoir formations suitable for carbon dioxide storage within the anticline. The correlation of the identified layers reflects the lithology and structure of the rock series. It allows determination of the thicknesses of the series and changes within them, and enables linking the individual layers with the lithologic units, based on geological data. The study refers to the whole Zechstein-Mesozoic succession of the Choszczno Anticline, with special emphasis on these series, in which there are potential reservoir formations for CO2 storage. The interpretation has significantly expanded the amount of data provided in standard seismic documentations. While assessing the suitability of the formations for CO2 storage, special attention should be paid to the tectonic disturbances within the Komorowo Formation, especially in the top part of the Choszczno structure. The Reed Sandstone bed is more continuous in this respect. The obtained results seem to suggest wider application of reprocessing of seismic materials into effective reflection coefficients to study the geological structure, also for other structures.

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Authors and Affiliations

Lidia Dziewińska
Radosław Tarkowski
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Abstract

This paper presents the results of an analysis of selected seismic profiles (reflection and refraction data) from the Radom-Lublin area aimed at obtaining a better understanding of geological structure and the identification of hydrocarbon deposits. To accurately reproduce the seismic reflection covering the sub-Permian formations, seismic cross sections were interpreted based on effective reflection coefficients (ERC). In interpreting the results, reference was made to the results of studies of the area using other geophysical methods.
The results of these studies made it possible to obtain new information on the geology and structure of the Paleozoic complex of the Radom-Lublin area and its relationships with the basement tectonics. The structural arrangement of Carboniferous and Devonian formations as well as older Silurian, Ordovician, and Cambrian series were recognized. Selected significant tectonic and lithological discontinuities and the nature and directions of their course were characterized. Special attention was given to regional tectonic zones: the Skrzynno Fault, the Ursynów-Kazimierz fault zone and the Kock zone. The use of ERC methodology made it possible to define the boundaries of lithostratigraphic units in Carboniferous, Devonian, and older formations. The obtained results can be used to assess hydrocarbon accumulation in the area under consideration.
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Authors and Affiliations

Lidia Dziewińska
1
ORCID: ORCID
Radosław Tarkowski
1
ORCID: ORCID

  1. Mineral and Energy Economy Research Institute, Polish Academy of Sciences, Kraków, Poland
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Abstract

Effective use of energy in various branches of economy is one of world trends in development of power engineering. Relevant energy consumption occurs during exploitation of buildings, so there is still potential to diminish it as far as heating, ventilation, and air conditioning are concerned. Particularly in summer season, the choice of respective roofing colour can play a decisive role for the heat flux transferred to the inside of the object. Decrease of heat flux causes a lower heat burden to the building and lower power consumption by the air conditioning systems. In winter, on the contrary, heat flux transferred to building’s interior should be higher, as a result, demand of energy for heating will be lower. However, calculations of the heat flux require that energy balance must be made for the object. Unfortunately, not all producers of roofing covers inform about the values of reflectivity and thermal emissivity of their products, which is, in turn, necessary for calculations. In the present paper, research methodology elaborated by authors is proposed for determination of thermal emissivity of roofing covers. The paper presents test stand, methodology, and research results for roofing paper in blue colour (as an example) for which the thermal emissivity is an unknown parameter.

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Authors and Affiliations

Zbigniew Zapałowicz
Anna Walterowicz
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Abstract

The aim of the paper is to experimentally determine the scattering matrix S of an example reflective muffler of cylindrical geometry for Helmholtz number exceeding the plane wave propagation. Determining the scattering matrix of an acoustic systems is a new and increasingly used approach in the assessment of reduction of noise propagating inside duct-like elements of heating, ventilation and air conditioning systems (HVAC). The scattering matrix of an acoustic system provides all necessary information on the propagation of wave through it. In case of the analysed reflective silencer, considered as a two-port system, the noise reduction was determined by calculating the transmission loss parameter (TL) based on the scattering matrix (S). Measurements were carried out in two planes of the cross-section of pipes connected to the muffler.

The paper presents results of the scattering matrix evaluation for the wave composed of the plane wave (mode (0,0)) and the first radial mode (0,1), each of which was generated separately using the self-designed and constructed single-mode generator. The gain of proceeding measurements for single modes stems from the fact that theoretically, calculation of the S-matrix does not require, as will be presented in the paper, calculation of the measurement data inverse matrix. Moreover, if single mode sound fields are well determined, it ensures error minimization. The presented measurement results refer to an example of a duct like system with a reflective muffler for which the scattering matrix S was determined. The acoustic phenomena inside such a system can be scaled by the parameter ka.
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Authors and Affiliations

Łukasz Gorazd
1

  1. AGH University of Science and Technology, Faculty of Mechanical Engineering and Robotics, Kraków, Poland
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Abstract

Sub-bottom profiler (SBP) is an acoustic instrument commonly used to survey underwater shallow geological structure and embedded objects whose most important performance parameter is the actual vertical resolution. This paper presented a methodology to measure and evaluate the actual vertical resolution of SBP based on an experiment in an anechoic tank, which was divided into three components: building of artificial geological model, measurement of acoustic parameters, and determination of actual vertical resolution of the acoustic profiles. First, the wedge-shaped geological model, whose thickness could be accurately controlled, was designed and built in an anechoic tank to try to directly measure the vertical resolution of SBP. Then, the acoustic pulse width of SBP was measured to calculate the theoretical general vertical resolution and extreme vertical resolution. Finally, based on the acoustic profiles obtained in the experiment, the method which was used to evaluate the actual vertical resolution by measuring the duration of reflection event was put forward. Due to comparing measurement data of different parameter settings of the SBP, the study has revealed that the SBP had the lowest resolution in the 4 kHz–500 µs setting, which was 226.5 µs, or 36.2 cm, and the highest resolution in the 15 kHz–67 µs setting, which was 72.7 µs, or 11.6 cm. The vertical resolution decreased with the increase of the pulse width. The results also showed that the actual resolution was close to the theoretical general resolution and far from the extreme resolution.

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Authors and Affiliations

Fangqi Wang
Lifeng Dong
Jisheng Ding
Xinghua Zhou
Changfei Tao
Xubo Lin
Guanhui Liang
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Abstract

One of the main issues of design process of HVAC systems and ventilation ducts in particular is correct modelling of coupling of the flow field and acoustic field of the air flowing in such systems. Such a coupling can be modelled in many ways, one of them is using linearised Euler equations (LEE). In this paper, the method of solving these equations using finite element method and open source tools is decribed. Equations were transformed into functional and solved using Python language and FEniCS software. The non-reflective boundary condition called buffer layer was also implemented into equations, which allowed modelling of unbounded domains. The issue, influence of flow on wave propagation, could be adressed using LEE equations, as they take non-uniform mean flow into account. The developed tool was verified and results of simulations were compared with analytical solutions, both in one- and two-dimensional cases. The obtained numerical results are very consistent with analytical ones. Furthermore, this paper describes the use of the developed tool for analysing a more complex model. Acoustic wave propagation for the backward-facing step in the presence of flow calculated using Navier-Stokes equations was studied.

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Authors and Affiliations

Paweł Łojek
Ireneusz Czajka
Andrzej Gołaś

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