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Abstract

Global brown coal resources are estimated to be extracted at around 512 million Mg. They are found in over a dozen countries, including primarily: Australia, China, the Czech Republic, Greece, Germany, Poland, Russia, the United States and Turkey. More than 80% of total brown coal production in the EU takes place in: Germany, Poland, Greece and the Czech Republic. This means that the majority of production still uses conventional fuels, including both hard coal and brown coal. Given the current energy needs in the context of brown coal reserves depletion and the impacts of the current climate and energy policies of the EU, it is very important that all new investments in mining and energy complexes based on brown coal resources must be prepared carefully to ensure high production efficiency and minimize negative environmental impacts. This article attempts to solve a problem involving the choice of the location of the opening cut to expose brown coal deposits. Due to the stratified nature of brown coal deposits and the associated open-cast mining technology used in a continuous mining system with bucket wheel excavators, belt conveyor systems and spreaders, the location of the opening cut is not completely random and the number of potential solutions is finite. The multifaceted technical, organizational, economic, social and environmental problems require a holistic approach to this research problem. Such an approach should take the different, often opposing, perspectives of the many stakeholders into account. These issues can be solved using mathematical tools designed for multiple-criteria decision support. With the proposed method, a ranking of alternatives can be created, depending on the predefined location of the opening cut.

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Authors and Affiliations

Mateusz Henryk Sikora
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Abstract

The image analysis consists in extracting from the information which is available to the observer of the part that is important from the perspective of the investigated process. This process usually accompanies a considerable reduction in the amount of information from the image. In the field of two-phase flows, computer image analysis can be used to determine flow and geometric parameters of flow patterns. This article presents the possibilities of using this method to determine the void fraction, vapor quality, bubble velocity and the geometric dimensions of flow patterns. The use of computer image analysis methods is illustrated by the example of HFE 7100 refrigerant methoxynonafluorobutane condensation in a glass tubular minichannel. The high speed video camera was used for the study, and the films and individual frames received during the study were analyzed.

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Authors and Affiliations

Małgorzata Sikora
Tadeusz Bohdal
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Abstract

Nowadays, in addition to the thermodynamic properties of refrigerants, their impact on the environment is of high significance. Hence, it is important to use refrigerants with the lowest possible values of ozone depletion potential and global warming potential indices in refrigeration, organic Rankine cycle (ORC), air conditioning, and heat pump systems. Natural refrigerants are the most environmentally friendly; unfortunately, they have less favourable thermodynamic properties. Currently, low-pressure refrigerants from the FC (fluorocarbons, fluorine liquids) and HFE (hydrofluoroether) groups are increasingly used. This paper presents the most important properties and applications of selected refrigerants from these groups and also reviews the literature on their use.
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Authors and Affiliations

Małgorzata Sikora
1
Tadeusz Bohdal
1

  1. Koszalin University of Technology, Śniadeckich 2, 75-453 Koszalin, Poland
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Abstract

Żyjemy dziś dłużej niż nasi przodkowie. Wiąże się to z zachorowalnością na choroby wieku podeszłego. Dobrą profilaktyką tych chorób może się okazać spowalnianie procesu starzenia.
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Authors and Affiliations

Ewa Sikora
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Abstract

In the over 150 years of hydrocarbon history, the year 2017 will be one of the many similar. However, it will be a breakthrough year for liquefied natural gas. In Asia, China grew to become the leader of import growth, becoming the second world importer, overtaking even South Korea and chasing Japan. The Panama Canal for LNG trade and the “Northern Passage” was opened, so that Russian LNG supplies appeared in Europe. The year 2017 was marked by a dramatic shortening of the length of long-term concluded contracts, their shorter tenure and reduction of volumes – that is, it was another period of market commoditization of this energy resource. The article describes the current state of LNG production and trade till 2018. It focuses on natural gas production in the United States, Qatar, Australia, Russia as countries that can produce and supply LNG to the European Union. The issue of prices and the contracts terms in 2017 was analyzed in detail. The authors stress that the market is currently characterized by an oversupply and will last at least until mid–2020. Novatek, Total – Yamal-LNG project leaders have put the condensing facility at 5.5 million tons into operation. The Christophe de Margerie oil tanker was the first commercial unit to cross the route to Norway and then further to the UK without icebreakers and set a new record on the North Sea Road. In 2017, the Russian company increased its share in the European gas market from 33.1 to 34.7%. In 2017, Russia and Norway exported record volumes of „tubular” – classic natural gas to Europe (and Turkey), 194 and 122 billion m3 respectively, which is 15 and 9 billion m3 more natural gas than in 2016. The thesis was put forward that Russia would not easily give up its sphere of influence and would do everything and use various mechanisms, not only on the market, that it would simply be more expensive and economically unprofitable than natural gas. It was also emphasized that the pressure of the technically possible and economically viable redirection to European terminals of methane carriers landed in the American LNG, results in Gazprom not having a choice but to adjust its prices. The Americans, but also any other supplier (Australia?) can simply do the same and this awareness alone is enough for Russian gas to be present in Europe at a good price.

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Authors and Affiliations

Andrzej P. Sikora
Mateusz Sikora
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Abstract

This paper shall present and explain the key aspects related to the issue of combined heat and power generation (CHP – Combined Heat and Power or Cogeneration). The cooperation with the water treatment plant launched allowed a closer look at the described technology as well as allowed the analyses and survey. The survey on the efficacy of the selected components of the cogeneration system was based on two cogeneration units fuelled with biogas produced in the sewage fermentation.
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Authors and Affiliations

Karol Tucki
Michał Sikora
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Abstract

The article analyses selected aspects of the technology and logistics used to modernise a coal-fired heating plant to switch to woodchips, which is illustrated with a specific investment. The study presents characteristics of the investment’s heat economy before the modernisation, as well as the assumptions and program of the project. Finally, selected effects of the modernisation have been described
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Authors and Affiliations

Karol Tucki
Michał Sikora
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Abstract

Housing resources as an element of material infrastructure determine socio-economic development on a local, regional and national scale. Their economic and physical accessibility affects the development of human, social and relational capital, determines the competitiveness of the territory and can be seen as a generator of income both in the individual sense and in relation to the whole society. The article has a theoretical character and its aim is to identify the relationship between satisfying the housing needs of local communities and the development of territorial capital. The article also analyzes factors that allow the qualification of housing resources as a strategic resource for the development of a territory.

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Authors and Affiliations

Dorota Sikora-Fernandez
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Abstract

Investigations of refrigerant condensation in pipe minichannels are very challenging and complicated issue. Due to the multitude of influences very important is mathematical and computer modeling. Its allows for performing calculations for many different refrigerants under different flow conditions. A large number of experimental results published in the literature allows for experimental verification of correctness of the models. In this work is presented a mathematical model for calculation of flow resistance during condensation of refrigerants in the pipe minichannel. The model was developed in environment based on conservation equations. The results of calculations were verified by authors own experimental investigations results.

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Authors and Affiliations

Małgorzata Sikora
Tadeusz Bohdal
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Abstract

This paper presents a study of the effect of the modification and cooling rate on the grain count α(Al) in the Al-5Cu alloy. Research was

performed on castings with walls thickness between 3 mm and 25 mm. Cooling curves were recorded to determine the cooling rate and the

degree of undercooling at the beginning of solidification. It has been shown that cooling rate increases exponentially as the wall thickness

of casting decreases. Moreover it has been demonstrated that the cooling rate of castings changes within a wide range (21ºC/s - 1ºC/s)

when the wall thickness changes from 3 up to 25 mm. Metallographic examinations revealed primary grains (primary α(Al) grains). The

paper show that the relationship between the grain count and the degree of undercooling (for non-modified and modified alloys) can be

represented by the equation N = Nv = np·exp(-b/ΔTα), based on the Weibull's distribution of the size of nucleation sites.

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Authors and Affiliations

M. Górny
G. Sikora
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Abstract

The article describes how to identify the boundary and yield surface for hypoplastic constitutive equations proposed by Wu, Gudehus and Bauer. It is shown how to identify and plot the surfaces for any equation in this class. Calculation errors are analyzed characteristic for applied set of numerical formulas. In the paper there are computer links to the source code prepared in the MATLAB system, based on instructions in the article. A sample consitutive domains are shown, plotted using the attached computer program.

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Authors and Affiliations

Z. Sikora
P. Cieśla
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Abstract

Attempts to perform synthesis of a passive vibroinsulation two-mass system intended for the simultaneous reduction of machine frame vibrations and forces transmitted to foundations by supporting elements were undertaken in the study. In view of the variable frequency of the machine operation, it was necessary for the frequency interval, encompassed by the vibroinsulation system operation, to be within given limits. On the grounds of properties of the linear massive-elastic system formulated in the works of Genkin and Ryaboy (1998), the problem of vibroinsulation system synthesis was formulated in the parametric type optimisation approach with equality and inequality limitations. For piston compressor vibroinsulation, the mass and elasticity matrices of the vibroinsulating system, as well as its physical structure, were determined. Its operation was verified on the basis of simulation investigations, taking into account the system loss and transient states.

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Authors and Affiliations

Grzegorz Cieplok
Marian Sikora

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Abstract

The article is dedicated to the determination of the types and functions of “someone else’s word”, i.e. intertextual relationships, present in political dramas of contemporary Russian writers. The author focuses on two types of intertexts such as quotes and allusions; determines their importance to the dramatic work as a whole, and distinguishes topic-related groups of texts to which dramatists refer. The conclusions of the study incline to place the phenomenon of political drama between what is “literary” and “social”, “eternal” and “up-to-date”.The analysis was carried out on the materials of dramas such as: Putin.doc by Victor Teterin, Sentry (Часовой) by Siergiej Reshetnikov, Meat by Olga Pogodina, and Beria by Dmitry Karapuzov.

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Authors and Affiliations

Paulina Sikora-Krizhevska
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Abstract

In the paper finite-dimensional semilinear dynamical control systems described by fractional-order state equations with the Hilfer fractional derivative are discussed. The formula for a solution of the considered systems is presented and derived using the Laplace transform. Bounded nonlinear function �� depending on a state and controls is used. New sufficient conditions for controllability without constraints are formulated and proved using Rothe’s fixed point theorem and the generalized Darbo fixed point theorem. Moreover, the stability property is used to formulate constrained controllability criteria. An illustrative example is presented to give the reader an idea of the theoretical results obtained. A transient process in an electrical circuit described by a system of Hilfer type fractional differential equations is proposed as a possible application of the study.
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Authors and Affiliations

Beata Sikora
1
ORCID: ORCID

  1. Department of Applied Mathematics, Silesian University of Technology, Kaszubska 23, 44-100 Gliwice, Poland

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