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Abstract

New types of models can help us better predict how well species will be able to adapt to climate change.
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Authors and Affiliations

Katarzyna Sękiewicz
1

  1. Department of Biogeography and SystematicsInstitute of Dendrology PAS in Kórnik
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Abstract

Comparative calculations with a mathematical model designed by the authors, which takes into consideration energy transfer from gas flowing through a given channel to gas which penetrates this channel from an adjacent channel, as well as a model which omits this phenomenon, respectively, were made for the process of separating gas mixtures carried out with an inert sweep gas in the fourend capillary membrane module. Calculations were made for the process of biogas separation using a PMSP polymer membrane, relative to helium as the sweep gas. It was demonstrated that omitting the energy transfer in the mathematical model might lead to obtaining results which indicate that the capacity of the process expressed by the value of feed flux subjected to separation is by several percent higher than in reality.
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Authors and Affiliations

Maciej Szwast
Zbigniew Szwast
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Abstract

Optimization of dialysis needs methods for quantitative assessment of fluid and solutes transport in body compartments and solute

and fluid exchange between body and dialysate. A mathematical model describing the dynamics of these quantities during dialysis is presented. This model is first and foremost based on the existing models, but also includes some new solutions. All parts were combined and extended by the detailed descriptions of selected aspects. The “virtual patient” model was applied to simulate and test different methods of treatment and their influence on the condition of the patient. The purpose of this model is to serve as a decision support system for selection of “optimal” treatment options for particular patient.

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Authors and Affiliations

M. Gałach
A. Weryński
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Abstract

Mathematical models offer certain solutions to social problems, but implementing them in practice may spark certain controversies – says Prof. Piotr Dworczak from Northwestern University.
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Authors and Affiliations

Piotr Dworczak
1

  1. Northwestern University
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Abstract

Machine learning methods, such as the random forests algorithm, have revolutionized how we analyze growing volumes of data. The algorithm can be usefully applied in studying… real forests.
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Authors and Affiliations

Łukasz Pawlik
1
Marcin K. Dyderski
2

  1. Institute of Earth Sciences,Faculty of Natural Sciences,University of Silesia in Katowice
  2. Institute of Dendrology,Polish Academy of Sciences in Kórnik
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Abstract

Predictive mathematical models have useful applications in the food industry – preventing the loss and wastage of food, thereby conserving resources.
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Authors and Affiliations

Elżbieta Rosiak
1

  1. Institute of Human Nutrition SciencesWarsaw University of Life Sciences (SGGW)
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Abstract

The aim of the work was to develop a mathematical model using equations of fluid mechanics that describe the dynamics of air flow in a part of the compost aerating system integrated with a stationary reactor. The results of the simulation show that adjusting the flow resistance along the entire length of the compost aerating duct, depending on the distance from the connection of the duct with the fan's pressure conduit pipe through gradually increasing the air outflow area by increasing the number of repeatable gaps, yields a uniform pressure distribution above the grate. The process parameters used for computation were relevant to composting a subscreen fraction separated from mixed municipal waste using 80 mm mesh screen (Fr<80 mm) under real conditions. Microsoft EXCEL 2010 software and STATISTICA version 13.3 by StatSoft were used for numerical and statistical analysis of the test results. The research results are presented in four tables and five figures and discussed in the text of the article. During tests performed in real conditions, various variants were tested for reactor filling level and air outflow active surfaces in subsequent grate parts (Fc (i)). It was found that the target waste layer thickness i.e. 3.0 m and Fc (i) changes, in accordance with the values of the developed model, result in a stable pressure distribution pd, amounting to 1506 Pa and 1495 Pa at the grate front and end part.
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Bibliography

  1. Bernat, K., Kulikowska D., Wojnowska-Baryła, I. & Kamińska A. (2022). Can the biological stage of a mechanical biological treatment plant that is designed for mixed municipal solid waste be successfully utilized for effective composting of selectively collected biowaste, Waste Management, 149, pp. 291-301. DOI:10.1016/j.wasman.2022.06.025
  2. Cui, C., Zhang, X. & Cai W. (2020). An energy-saving oriented air balancing method for demand controlled ventilation systems with branch and black-box model, Appl. Energy, 264, 11473. DOI:10.1016/j.apenergy.2020.114734
  3. Frederickson, J., Boardman, C.P., Gladding, T.L., Simpson, A.E., Howell G. & Sgouridis, F. (2013). Biofilter performance and operation as related to commercial composting. US Environment Agency 2013.
  4. Gałwa-Widera, M. & Kwarciak-Kozłowska, A. (2016). Methods for elimination of odor in the composting process, Rocznik Ochrona Środowiska, 18, pp. 850-860.
  5. Guohui, G. (2017). Dynamic thermal simulation of horizontal ground heat exchangers for renewable heating and ventilation of buildings, Renewable Energy, 103, pp. 361-371. DOI:10.1016/j.renene.2016.11.052
  6. https://www.horstmann.pl
  7. https://www.aknova.pl
  8. https://www.sutco.pl
  9. Jędrczak, A. & Den Boer, E. (2015). Final report of the 3rd stage of an expert opinion aimed at conducting waste tests in 20 installations for mechanical-biological waste treatment. https://sdr.gdos.gov.pl/Documents/GO/Ekspertyzy.
  10. Kisielewska, M., Dębowski, M. & Zieliński, M. (2020). Comparison of biogas production from anaerobic digestion of microalgae species belonged to various taxonomic groups. Archives of Environmental Protection, vol. 46, pp. 33-40. DOI:10.24425/aep.2020.132523
  11. Klimek, A., Rolbiecki, S. & Rolbiecki R. (2018). Effects of mulching with forest litter and compost made of sewage sludge on the presence of oribatida as bioindicators of soil revitalization in larch and pine in-ground forest nurseries, Rocznik Ochrona Środowiska, 20, pp. 681-696.
  12. Lanzerstorfer, Ch., Neder, F. & Schmied, R. (2016). Constant design air flow industrial ventilation systems with regenerative dust filters: Economic comparison of fan speed-controlled air damper controlled and uncontrolled operation, Energy and Buildings, 128, pp. 503–510. DOI:10.1016/j.enbuild.2016.07.032
  13. Lubczyńska, U. (2017). Applied hydraulic in environmental engineering. Publishing House, Kielce University of Technology, 2017.
  14. Nguyen, T.P., Koyama, M. & Nakasaki, K. (2022). Effects of oxygen supply rate on organic matter decomposition and microbial communities during composting in a controlled lab-scale composting system, Waste Management, Vol. 153, pp. 275-282. DOI:10.1016/j.wasman.2022.09.004
  15. Nogueira Da Silva Vilela, R., Amorim Orrico, C.A., Previdelli Orrico Junior, M.A., Aspilcueta Borquis, R.R., Dias de Oliveira, M.T.J., De Avila M. R., Torres dos Santos, F. & Viana Leite, B.K. (2022). Effects of aeration and season on the composting of slaughter house waste, Environmental Technol. & Innov, 27, 102505. DOI:10.1016/j.eti.2022.102505
  16. Pączka, G., Garczyńska, M., Mazur-Pączka, A., Podolak, A., Szura, R., Skoczko, I. & Kostecka, J. (2018). Vermicomposting of sugar beet pulps using Eisenia Fetida (sav.) earthworms, Rocznik Ochrona Środowiska, 20, pp. 588-601.
  17. Ross, H. (1995). Hydraulik der wasserheizung Oldenbourg, Verlag GmbH, Monachium 1995. Rudnik E. (2019). Chapter 5 - Composting methods and legislation, Compostable Polymer Materials 2.nd Edition, pp. 127-161. DOI:10.1016/b978-0-08-099438-3.00005-7
  18. Sadeghi, S., Nikaeen, M., Mohammadi, F., Nafez, A.H., Gholipour, S., Shamsizadeh, Z. & Hadi, M. (2022). Microbial characteristics of municipal solid waste compost: Occupational and public health risks from surface applied compost, Waste Management, 144, pp.98-105. DOI:10.1016/j.wasman.2022.03.012
  19. Sidełko, R., Janowska, B., Szymański, K., Mostowik, N. & Głowacka, A. (2019). Advanced methods to calculation of pressure drop during aeration in composting process, Science of the Total Environment, 674, pp. 19-25. DOI:10.1016/j.scitotenv.2019.04.155
  20. Sidełko, R., Seweryn, K. & Walendzik, B. (2011). Optimization of Composting Process in Real Conditions, Rocznik Ochrona Środowiska, 13, pp. 681-691.
  21. Sidełko, R. & Chmielinska-Bernacka, A. (2013). Application of Compact Reactor for Methane Fermentation of Municipal Waste, Rocznik Ochrona Środowiska, 15, pp. 683-693.
  22. Singley, M.E., Higgins, A.J. & Frumkin-Rosengaus, M. (1982). Sludge composting and utilization- A design and operating manual, New Jersy Arg. Expt. Sta., Rutgers Utility, 1982.
  23. Sundberg, C. & Jönsson, H. (2008). Higher pH and faster decomposition in biowaste composting by increased aeration, Waste Management, Vol. 28, pp. 518-526. DOI:10.1016/j.wasman.2007.01.011
  24. Szymański, K., Janowska, B., Sidełko, R. & Siebielska, I. (2007). Monitoring of waste landfills, VIII National Polish Scientific Conference on Complex and Detailed Problems of Environmental Engineering, Issue 23, pp. 75-133.
  25. Vaverkova, M.D., Elbl, J., Voberkova, S., Koda, E., Adamcova, D., Gusiatin, Z.M., Abd, Al Rahman, Radziemska, M. & Mazur, Z. (2020). Composting versus mechanical–biological treatment: Does it really make a difference in the final product parameters and maturity, Waste Management, 106, pp. 173-183. DOI:10.1016/j.wasman.2020.03.030
  26. Yi, W., Ran, G. Li, A., Zhiguo, G., Ni, Q., Yang, Y., Liu, B. & Du, Y. (2022). Air balancing method of multibranch ventilation systems under the condition of nonfully developed Flow, Boulding and Environment, 223. DOI:10.1016/j.buildenv.2022.109468
  27. Wang, X., Bai, Z., Yao, Y., Gao, B., Chadwick, D., Chen, Q., Hu, Ch. & Ma, L. (2018). Composting with negative pressure aeration for the mitigation of ammonia emissions and global warming potential, J. of Cleaner Production, 195 (10), pp. 448-557. DOI:10.1016/j.jclepro.2018.05.146
  28. Zhou, Y., Xiao, R., Klammsteiner, T., Kong, X., Yan, B., Mihai, F.C., Liu, T., Zhang, Z. & Awasthi, K.M. (2022). Recent trends and advances in composting and vermicomposting technologies: A review, Bioresources Technology, 360, 127591. DOI:10.1016/j.biortech.2022.127591
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Authors and Affiliations

Robert Sidełko
1
Dariusz Boruszko
2
ORCID: ORCID

  1. Koszalin University of Technology, Poland
  2. Bialystok University of Technology, Poland
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Abstract

The enzymatic synthesis of a highly hydrophobic product (dipeptide precursor) in which the reaction is accompanied by the mass transfer of the reaction product to the organic phase and the substrates to the water phase is considered. Equations describing both continuous and batch processes are formulated. The range of variability in the operating parameters of such a bioreactor is specified, and the correlations reported in the literature to describe mass transfer in the membrane contactor are validated. The proposed process was verified experimentally, and good agreement between the determined and calculated concentrations was obtained in both phases.

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Authors and Affiliations

Andrzej Noworyta
Anna Trusek-Holownia
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Abstract

The article presents a zero-dimensional mathematical model of a tubular fuel cell and its verification on four experiments. Despite the fact that fuel cells are still rarely used in commercial applications, their use has become increasingly more common. Computational Flow Mechanics codes allow to predict basic parameters of a cell such as current, voltage, combustion composition, exhaust temperature, etc. Precise models are particularly important for a complex energy system, where fuel cells cooperate with gas, gas-steam cycles or ORCs and their thermodynamic parameters affect those systems. The proposed model employs extended Nernst equation to determine the fuel cell voltage and steadystate shifting reaction equilibrium to calculate the exhaust composition. Additionally, the reaction of methane reforming and the electrochemical reaction of hydrogen and oxygen have been implemented into the model. The numerical simulation results were compared with available experiment results and the differences, with the exception of the Tomlin experiment, are below 5%. It has been proven that the increase in current density lowers the electrical efficiency of SOFCs, hence fuel cells typically work at low current density, with a corresponding efficiency of 45–50% and with a low emission level (zero emissions in case of hydrogen combustion).
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Authors and Affiliations

Janusz Badur
Marcin Lemański
Tomasz Kowalczyk
Paweł Ziółkowski
Sebastian Kornet
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Abstract

At the Kielce University of Technology a new concept of accurate measurements of sphericity deviations of machine parts has been developed. The concept is based upon measurement of roundness profiles in many clearly defined cross-sections of the workpiece. Measurements are performed with the use of typical radial measuring instrument equipped with a unit allowing accurate positioning of the ball. The developed concept required finding a solution to numerous problems relating to the principle of the radial measurement. One of the problems to be solved was matching of measured roundness profiles. The paper presents an outline of the developed concept of sphericity measurement, a mathematical model of profile matching and results of the verification of the model.

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Authors and Affiliations

Krzysztof Stępień
Dariusz Janecki
Stanisław Adamczak
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Abstract

The purpose of the article is to substantiate the basic conceptual provisions for determining the territorial development of regional land use. In accordance with the purpose, the following tasks have been solved: substantiation of theoretical provisions for determining the territorial development of regional land use; determination of features of territorial development of regional land use; formation of hypotheses on the influence of spatial, urban, investment and environmental factors. Peculiarities of territorial development of regional land use are determined. Legal support is proposed. The international practices for ensuring the territorial development of regional land use are summarized, the main directions of which are: the formation and development of land relations on a long-term basis, the determination of the target and functional purpose of lands, the constant registration of cadastral information with the formation of an ecological balance of the land use and considering the peculiarities of interaction between groups of stakeholders. The system of land administration, where its functions (land ownership, valuation, use, development of land) are comprehensively implemented and interact, in the territorial development of regional land use is of particular importance. The geographic information systems are widely used as a tool for the formation, processing and application of information on the territorial development of the regional land use in modern land administration systems. The mathematical modelling of the influence of factors on the territorial development of regional land use has been carried out.
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Bibliography

Blandinier, J.P. (2001). Problems of urban planning and landscaping. Economics. Finan´nes. Law 3, 3–4.

Dorosh, O.S. (2004). Management of land resources at the regional level. Kyiv: TOV “TSZRU”.

Hutsulyak, Y.D. (2002). Management of land resources in the conditions of market economy. Chernivtsi: Prut.

Kaminetska, O.V. (2017). Methodological basis of the research department of land resource potential areas. Agrosvit, 13, 39–42,

Mamonov, K. (2019). Territorial development of land use in the region: definition, evaluation and directions of transformations: a monograph. Kharkiv: FOP Panov AM.

Mamonov, K. (2020). Territorial development of land use in the region: directions and features of evaluation: a monograph. Kharkiv: O.M. Beketov NUUE.

Martin, A.G. (2011). Land market regulation in Ukraine: monograph. Kyiv: AgrarMediaGroup.

Palekha, Y.M. (2009). Theory and practice of evaluation of territories value and land valuation of settlements of Ukraine (economic-geographical research). ScD thesis. Kyiv: Institute of Geography of the National Academy of Sciences of Ukraine.

Perovich L. (2011). Current state and development prospects cadastral system in Ukraine. Modern achievements of geodesic science and industry, 2(22), 40–42.

Petrakovska, O. (2005). Fundamentals of urban land management methodology. Regional Problems of Architecture and Urban Planning, 8, 386–391.

Shipulin, V.D. (2014). Perspective of land administration. Land Management Bulletin, 5, 35–39.

Shipulin, V.D. (2016). System of land administration: basics of modern theory: a textbook. Kharkiv: KhNUMG named after OM Beketov.

State Geocadastre. (2018). Monitoring of land relations in Ukraine: 2016–2017. Statistical yearbook. Retrieved May 2021, from: https://land.gov.ua/wp-content/uploads/2018/10/monitoring.pdf.

State Statistics Service of Ukraine. (2020). Retrieved May 2021, from: http://www.ukrstat.gov.ua.

Stupen, M., Radomsky, S., Taratuta, R. (2011). Efficiency of agricultural land use in the agricultural sector of Zakarpattia region. Economist, 2, 30–32.

Tretiak, A., Tretiak, V., Kovalyshyn, O. et al. (2016). Improvement of the technique of rural lands assessment in Ukraine. Economist. Land relations, 5, 38–40.

Tretyak, A.M. and Babmindra, D.I. (2003). Land resources of Ukraine and their use. Kyiv: CZRU LLC.

Williamson, I., Enemark, S., Wallace, J. et al. (2010). Land administration for sustainable development. Retrieved May, 2021, from Esri Press http://www.esri.com/landing-pages/industries/landadministration/e-book#sthash.KF25CaWH.dpbs.
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Authors and Affiliations

Kostiantyn Mamonov
1
ORCID: ORCID
Olena Kanivets
2
Kostiantyn Viatkin
1
Oleksii Voronkov
1

  1. O.M. Beketov National University of Urban Economy, Kharkiv, Ukraine
  2. Sumy National Agrarian University, Sumy, Ukraine
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Abstract

Skin dynamic termography supplemented by a mathematical model is presented as an objective and sensitive indicator of the skin prick test result. Termographic measurements were performed simultaneously with routine skin prick tests. The IR images were acquired every 70 s up to 910 s after skin prick. In the model histamine is treated as the principal mediator of the allergic reaction. Histamine produces vasolidation and the engorged vessels are responsible for an increase in skin temperature. The model parameters were determined by fitting the analytical solutions to the spatio-temporal distributions of the differences between measured and baseline temperatures. The model reproduces experimental data very well (coefficient of determination = 0.805÷0.995). The method offers a set of parameters to describe separately skin allergic reaction and skin reactivity. The release of histamine after allergen injection is the best indicator of allergic response. The diagnostic parameter better correlates with the standard evaluation of a skin prick test (correlation coefficient = 0.98) than the result of the thermographic planimetric method based on temperature and heated area determination (0.81). The high sensitivity of the method allows for determination of the allergic response in patients with the reduced skin reactivity.

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Authors and Affiliations

E. Rokita
T. Rok
G. Tatoń
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Abstract

In the projects of protection of soil-water environment there is a need to combine and process large amount of information from various disciplines to estimate parameters of phenomena and to determine the range and time table of necessary undertakings.

Due to complex assessment of processes taking place in aquifers, mathematical modeling is the best tool supporting evaluation off pollution in the ground water environment. It is also an effective method of forecasting the risk associated with the harmful impact of objects polluting grounds and grounds waters.

Significant application of mathematical modeling is the use for the enlargement of information gathered in the process of recognition and assessment of condition that prevail in soil-water environment. Results of modeling, if appropriately presented, could be an important element of decision support system in environmental management.

This paper describes procedures for developing an environmental remediation decision support system by linking CADD and GIS software with the hydro geological flow and transport models.

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Authors and Affiliations

Marek Ślesicki
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Abstract

The study concerns modeling and simulation of the growth of biofilms with heterogeneous structures with a discrete mathematical model based on theory of cellular automata. The article presents two-dimensional density distributions of biofilms for microbial processes: oxidation of ammonium by Nitrosomonas europaea bacteria and glucose utilization by Pseudomonas aeruginosa bacteria. The influence of limiting substrate concentration in the liquid phase on biofilm structure was determined. It has been shown that the value of death rate coefficient of microorganisms has the qualitative and quantitative influence on the density and porosity of the biofilm.

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Authors and Affiliations

Szymon Skoneczny
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Abstract

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.

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Authors and Affiliations

Szymon Skoneczny
Bolesław Tabiś
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Abstract

The lumbosacral region of the spine is the most susceptible to pathology in large breed dogs. The most common pathologies of this segment include intervertebral disc disease, distortion of vertebrae, narrowing of the lumbosacral canal and congenital defects of the spine. The aim of this study is to develop a mathematical model describing the height of each lumbosacral vertebra in the dog in relation to the position of the vertebra. For the mathematical analysis we used the results of two measurements for each lumbar vertebra. The first measurement was made from the top of the spinous process to the center of the spinal cord. The second measurement was made from the center of the body of one vertebra to the center of the body of the next one. It is possible to determine an approximate mathematical model that would be uniform for the entire species and would connect the height of the lumbar vertebrae with their location for every breed of the domestic dog. Despite the considerable differences in the constitutional type (small, medium and large breeds), the morphology of the lumbosacral region of the spine exhibits similar proportions. Therefore, it is possible to assess an anomaly of this spinal region objectively. These findings suggest that it is possible to determine an approximate mathematical model that would be uniform for the entire species. The present study was carried out as part of a larger project. This particular work is a pilot study.

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Authors and Affiliations

I. Wadowska
M. Dzierzęcka
S. Paśko
K. Barszcz
B.J. Bartyzel
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Abstract

The problems of mathematical modelling of vibration signal for bearings with specific geometrical structure or defect is important insofar as there are no model bearings (to facilitate carrying out a calibration procedure for industrial measurement systems). It is even more so that there are no precise reference systems to which we would compare the results. This article presents a general outline of the most important studies on modelling of vibrations in rolling bearings. Papers constituting the basis for the most recent studies and a review of articles from the past few years have been considered here. Five different models have been analyzed in detail in order to show the directions of the latest studies. Completed analysis presents different viewpoints on the issue of modelling a rolling bearing operation. This overview article makes it possible to derive the final conclusion that in order to include all factors affecting bearing vibrations, even those ignored in the most recent models, it is necessary to carry out practical statistical research including the principles of multicriteria statistics. This approach will facilitate developing a versatile model, also applicable to predicting vibrations of a new bearing just manufactured in a factory.

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Authors and Affiliations

M. Wrzochal
S. Adamczak
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Abstract

The paper describes a mathematical model of gas flow through crevices between the piston, rings and cylinder in internal combustion engines. The model has been developed to study the influence of numerous. design parameters and engine operation condition on piston ring pack behaviour and the exhaust gases blowby from the combustion chamber to the crankcase. The model integrates the gas flow and axial rings displacements in the grooves, and separately treats lands between piston, cylinder and adjacent rings and regions in the grooves behind the rings. The heat transfer between the gas and the surrounding surfaces is calculated and emphasis is placed on considering the influence of wear and thermal deformations of elements on ring pack performance.
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Authors and Affiliations

Grzegorz Koszałka
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Abstract

The paper presents a study of Rotary Electrical Discharge Machining (REDM) process. In REDM, simple shaped cylindrical electrodes are used to generate 3D complex shapes. A theoretical model of machining process is described, which takes into consideration the effect of tool electrode wear on machined surface profile. The software for computer simulation of REDM has been developed. In the paper, the effects of machining parameters on shape error of machined surface are discussed. Results of computer simulation have been confirmed in experimental practice. The simulation model for NC contouring REDM may also be applied to solving numerical control problems and optimization of tool electrode path.
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Authors and Affiliations

Jerzy Kozak
Zbigniew Gulbinowicz
Dorota Gulbinowicz
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Abstract

The paper presents computer application of the mathematical model of piston- ring-cylinder packing, which was described in detail in the first part of the paper. Methodology of selection of the input data, results of primary calculations and the method of model verification are also shown. The results allow acknowledging the mathematical model as verified.
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Authors and Affiliations

Grzegorz Koszałka
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Abstract

The paper presents a description of used methods and exemplary mathematical models which are classified into theoretical-empirical models of thermal processes. Such models encompass equations resulting from the laws of physics and additional empirical functions describing processes for which analytical models are complex and difficult to develop. The principle of developing, advantages and disadvantages of presented models as well as quality prediction assessment were presented. Mathematical models of a steam boiler, a steam turbine as well as a heat recovery steam generator were described. Exemplary calculation results were presented and compared with measurements.

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Authors and Affiliations

Henryk Rusinowski
Marcin Plis
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Abstract

In this paper a mathematical model enabling the analysis of the heat-flow phenomena occurring in the waterwalls of the combustion chambers of the boilers for supercritical parameters is proposed. It is a one-dimensional model with distributed parameters based on the solution of equations describing the conservation laws of mass, momentum, and energy. The purpose of the numerical calculations is to determine the distributions of the fluid enthalpy and the temperature of the waterwall pipes. This temperature should not exceed the calculation temperature for particular category of steel. The derived differential equations are solved using two methods: with the use of the implicit difference scheme, in which the mesh with regular nodes was applied, and using the Runge-Kutta method. The temperature distribution of the waterwall pipes is determined using the CFD. All thermophysical properties of the fluid and waterwall pipes are computed in real-time. The time-spatial heat transfer coefficient distribution is also computed in the on-line mode. The heat calculations for the combustion chamber are carried out with the use of the zone method, thus the thermal load distribution of the waterwalls is known. The time needed for the computations is of great importance when taking into consideration calculations carried out in the on-line mode. A correctly solved one-dimensional model ensures the appropriately short computational time.

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Authors and Affiliations

Wiesław Zima
Sławomir Grądziel
Artur Cebula
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Abstract

The paper presents a one-dimensional mathematical model for simulating the transient processes which occur in the liquid flat-plate solar collector tubes. The proposed method considers the model of collector tube as one with distributed parameters. In the suggested method one tube of the collector is taken into consideration. In this model the boundary conditions can be time-dependent. The proposed model is based on solving the equation describing the energy conservation on the fluid side. The temperature of the collector tube wall is determined from the equation of transient heat conduction. The derived differential equations are solved using the implicit finite difference method of iterative character. All thermo-physical properties of the operating fluid and the material of the tube wall can be computed in real time. The time-spatial heat transfer coefficient at the working fluid side can be also computed on-line. The proposed model is suitable for collectors working in a parallel or serpentine tube arrangement. As an illustration of accuracy and effectiveness of the suggested method the computational verification was carried out. It consists in comparing the results found using the presented method with results of available analytic solutions for transient operating conditions. Two numerical analyses were performed: for the tube with temperature step function of the fluid at the inlet and for the tube with heat flux step function on the outer surface. In both cases the conformity of results was very good. It should be noted, that in real conditions such rapid changes of the fluid temperature and the heat flux of solar radiation, as it was assumed in the presented computational verification, do not occur. The paper presents the first part of the study, which aim is to develop a mathematical model for simulating the transient processes which occur in liquid flat-plate solar collectors. The experimental verification of the method is a second part of the study and is not presented in this paper. In order to perform this verification, the mathematical model would be completed with additional energy conservation equations. The experimental verification will be carry out in the close future.

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Authors and Affiliations

Wiesław Zima
Piotr Dziewa
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Abstract

A steam generator in a nuclear power plant with a light water reactor is a heat exchanger, in which the heat is being transferred from the primary to the secondary loop (it links the primary and secondary loops). When the power plant is running, the inlet parameters (temperatures and mass flow rates) on both sides of the steam generator can change. It is important to know how the changes of these parameters affect the steam generator performance. The complexity of the processes taking place in the steam generator makes it difficult to create a simulator reflecting its performance under changed conditions. In order to simplify the task, the steam generator was considered as a ‘black box’ with the aim of examining how the changes of the inlet parameters affect the changes of the outlet ones. On the basis of the system (steam generator) response, a simple mathematical model of the steam generator under variable load conditions was proposed. In the proposed model, there are two dimensionless parameters and three constant coefficients. A linear relation between these dimensionless parameters was obtained. The correctness of the model was verified against the data obtained with a steam generator simulator for European Pressured Reactor and AP-600 reactors. A good agreement between the proposed model and the simulator data was achieved.

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Authors and Affiliations

Rafał Laskowski
Janusz Lewandowski

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