Nowe zasoby w kolekcji Artykuły i czasopisma http://suw.biblos.pk.edu.pl/ Biblioteka Politechniki Krakowskiej lipinska@biblos.pk.edu.pl 60 <![CDATA[Inorganic nanoparticle synthesis in flow reactors – applications and future directions]]> Fri, 23 Oct 2020 12:46:09 +0200 Długosz, Olga; Banach, Marcin
rodzaj: artykuł w czasopiśmie
Abstrakt: The popularity of nanotechnology results from the possibility of obtaining materials that have better chemical, electrical, thermal, mechanical, or optical properties. Until recently, nanoparticles were produced in batch processes. Numerous methods of nanomaterial synthesis have been described in the literature; however, the production of nanomaterials on a larger scale is still limited. The advantages of using flow processes are the possibilities of increasing the operating efficiency of the installation, which would respond to the growing demand for nanomaterials, as well as maintaining high purity products with well-defined physical and chemical properties. This review presents the latest achievements in the flow synthesis of metal nanoparticles, metal oxides, semiconductors and complex inorganic structures. Depending on the energy source, the products differ in size, shape, dispersion and stability, which determine their future properties. The choice of type of reactor prevents clogging of the reactor and deposition of particles on the walls of the channel. The purpose of this work is to analyze the state of knowledge regarding the production of inorganic nanoparticles by flow methods. This work is a review of the types of reactors used to obtain nanoparticles and the benefits and limitations of their use in industry. The introduction of flow technologies for obtaining nanoparticles can play an important role in the development of ecological and sustainable processes for obtaining nanomaterials, and the methods presented are part of the Flow Chemistry trend. Finally, this Review covers future directions of flow nanoparticle synthesis with conclusions and outlook.]]>
<![CDATA[Synthesis of Fe3O4/ZnO nanoparticles and their application for the photodegradation of anionic and cationic dyes]]> Fri, 23 Oct 2020 10:52:26 +0200 Długosz, O.; Szostak, K.; Krupiński, M.; Banach, M.
rodzaj: artykuł w czasopiśmie
Abstrakt: Multifunctional materials have become an important research subject in recent years. Zinc oxide nanoparticles (ZnO NP) deposited on iron oxide (Fe3O4) allow to obtain material with photocatalytic and magnetic properties. The mass share of Fe3O4 in the composite was 30%. Saturation magnetization for this sample was about 9.5 emu/g. The use of magnetic material allows to recover the photocatalyst after the photodegradation process and reuse it. The possibility of recovery of Fe3O4 nanoparticles with a magnet was estimated at 94.80%, while the recovery of Fe3O4/ZnO achieved 83.91%. The efects of the type of dyes (Methylene Blue, Methyl Orange, Quinoline Yellow, Eriochromic Black T and Trypanic Blue) on their photodegradation efciency in terms of molar mass of the dye, the solvent in which the processes were carried out and the type of dye charge were investigated. The photocatalytic material showed higher photodegradation activity of dyes while increasing their molar mass. ZnO NPs deposited on Fe3O4 presented 95.61% photocatalytic efciency against Trypan Blue and 63.02% against Methylene Blue. Increasing the surface area of the catalyst to 39 m2 /g and the presence of micro-, meso- and macropores had a positive efect on the sorption process of dyes, especially those of larger sizes, allowing their degradation in the photodegradation process.]]>
<![CDATA[Continuous synthesis of metal and metal oxide nanoparticles in microwave reactor]]> Fri, 23 Oct 2020 10:05:43 +0200 Długosz, Olga; Banach, Marcin
rodzaj: artykuł w czasopiśmie
Abstrakt: The aim of the study is to elaborate a universal method for obtaining metal (Ag and Cu) and metal oxide (CuO and SnO) nanoparticles (NPs) in a microwave flow reactor. The combination of microwave radiation energy with the flow-through process allows us to efficiently obtain NPs with accurate size control. The metal and metal oxide NPs synthesised by the microwave-assisted continuous method are characterised by ultraviolet-visible spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and dynamic light scattering. The results show the formation of spherical Ag, Cu and SnO NPs and CuO nanowires. In order to optimise the size of the NPs, the effects of reaction conditions, such as the concentration of stabiliser, irradiation time, pH of the solution and irradiation power of NP synthesis are studied. Under the most favourable reaction conditions, NPs with average diameters of 20 and 45 nm for Ag and Cu NPs, and 25 and 7 nm for SnO and CuO NPs, respectively, are obtained. The efficiency of the processes is 0.3–0.6 g/h for metal NP synthesis and 2.5–8.7 g/h for metal oxide NP synthesis.]]>
<![CDATA[Analiza właściwości ochronnych gruntobetonów wobec stali zbrojeniowej]]> Fri, 23 Oct 2020 08:32:52 +0200 Zdeb, Tomasz; Tracz, Tomasz; Żelazik, Mateusz
rodzaj: artykuł w czasopiśmie
Abstrakt: W artykule przedstawiono wyniki badań składu oraz odczynu pH fazy ciekłej wypełniającej pory gruntobetonów, pozyskanej metodą ługowania oraz ekstrakcji ciśnieniowej. Badania dotyczyły dwóch gruntobetonów wykonanych z różnego rodzaju gruntu rodzimego: sypkiego i spoistego, o różnych stosunkach w/c wprowadzanego do gruntu zaczynu cementowego, odpowiednio 0,8 i 2,0. Otrzymane wyniki badań składu fazy ciekłej, oznaczone metodą chromatografii jonowej, jak i pH, posłużyły do oceny właściwości ochronnych gruntobetonów wobec stali zbrojeniowej. Wyniki przeprowadzonych badań wskazują na pełną zdolność badanych gruntobetonów do ochrony stali przed korozją, a także na potencjalnie dużą trwałość ich samych. Ponadto, ze względu na podjętą próbę oznaczenia składu fazy ciekłej gruntobetonów dwiema metodami, w artykule poddano dyskusji poziom ich zróżnicowania pod kątem składu chemicznego.]]>
<![CDATA[Experimental study on fatigue failure evolution in composite plate monitored by wave propagation method]]> Thu, 22 Oct 2020 14:03:34 +0200 Stawiarski, Adam; Barski, Marek; Muc, Aleksander
rodzaj: artykuł w czasopiśmie
Abstrakt: In this study, the elastic wave propagation method is used to observe the initiation and evolution of the fatigue failure form in the multilayered composite plate with an elliptical hole. The experimental tests with the use of active, pitch-catch elastic wave measurement techniques are used during the fatigue test of the composite specimens. The fatigue tests were preceded by the numerical, finite element analysis of the elastic wave propagation phenomenon in a composite plate with an elliptical hole. The sequential measurement related to the number of cycles during the fatigue tests was assumed. The time of flight (ToF) and amplitude change was monitored by piezoelectric sensors localized in the area of predictable failure form evolution. The analysis of the dynamic response of the structure under fatigue loading conditions by a relatively small number of piezoelectric transduces allows us to build cost-effective Structural Health Monitoring (SHM) system for damage detection and monitoring of the failure form evolution.]]>
<![CDATA[The influence of the configuration of the fiber-metal laminates on the dispersion relations of the elastic wave modes]]> Thu, 22 Oct 2020 13:58:45 +0200 Barski, Marek; Muc, Aleksander; Stawiarski, Adam
rodzaj: artykuł w czasopiśmie
Abstrakt: The current work is devoted to the determination of dispersion curves for elastic wave modes. The studied elastic waves propagate across metal-fiber hybrid composites. In order to solve the problem, special software has been developed with the use of C++. This software works with the MS Windows operating system and the proposed solution is based on the multi-threading mechanism. It makes possible to significantly speed up the calculations. The relatively new approach is used namely the stiffness matrix method. At the very beginning, the dispersion curves are determined for the traditional composite materials of cross-ply configuration, for which the layers are made of glass fiber/epoxy resin and carbon fiber/epoxy resin. The impact of the total number of layers on the dispersion curves is investigated. Next, the influence of the thickness of the layers, which are made of aluminum alloy, on the dispersion characteristic is studied. In the second case, it is assumed that the total thickness of the composite material wall for all cases is identical.]]>
<![CDATA[Analysis of pedestrian activity before and during COVID-19 lockdown, using webcam time-lapse from Cracow and machine learning]]> Thu, 22 Oct 2020 13:58:02 +0200 Szczepanek, Robert
rodzaj: artykuł w czasopiśmie
Abstrakt: At the turn of February and March 2020, COVID-19 pandemic reached Europe. Many countries, including Poland imposed lockdown as a method of securing social distance between potentially infected. Stay-at-home orders and movement control within public space not only affected the touristm industry, but also the everyday life of the inhabitants. The hourly time-lapse from four HD webcams in Cracow (Poland) are used in this study to estimate how pedestrian activity changed during COVID-19 lockdown. The collected data covers the period from 9 June 2016 to 19 April 2020 and comes from various urban zones. One zone is tourist, one is residential and two are mixed. In the first stage of the analysis, a state-of-the-art machine learning algorithm (YOLOv3) is used to detect people. Additionally, a non-standard application of the YOLO method is proposed, oriented to the images from HD webcams. This approach (YOLOtiled) is less prone to pedestrian detection errors with the only drawback being the longer computation time. Splitting the HD image into smaller tiles increases the number of detected pedestrians by over 50%. In the second stage, the analysis of pedestrian activity before and during the COVID-19 lockdown is conducted for hourly, daily and weekly averages. Depending on the type of urban zone, the number of pedestrians decreased from 33% in residential zones to 85% in tourist zones located in the Old Town. The presented method allows for more efficient detection and counting of pedestrians from HD time-lapse webcam images compared to SSD, YOLOv3 and Faster R-CNN. The result of the research is a published database with the detected number of pedestrians from the four-year observation period for four locations in Cracow.]]>
<![CDATA[Natural convection in differentially heated enclosures subjected to variable temperature boundaries]]> Thu, 22 Oct 2020 13:34:57 +0200 Mohamad, Abdulmajeed; Sheremet, Mikhail A.; Taler, Jan; Ocłoń, Paweł
rodzaj: artykuł w czasopiśmie
Abstrakt: Purpose: Natural convection in differentially heated enclosures has been extensively investigated due to its importance in many industrial applications and has been used as a benchmark solution for testing numerical schemes. However, most of the published works considered uniform heating and cooling of the vertical boundaries. This paper aims to examine non-uniform heating and cooling of the mentioned boundaries. The mentioned case is very common in many electronic cooling devices, thermal storage systems, energy managements in buildings, material processing, etc. Design/methodology/approach: Four cases are considered, the left-hand wall’s temperature linearly decreases along the wall, while the right-hand wall’s temperature is kept at a constant, cold temperature. In the second case, the left-hand wall’s temperature linearly increases along the wall, while the right-hand wall’s temperature is kept a constant, cold temperature. The third case, the left-hand wall’s temperature linearly decreases along the wall, while the right-hand wall’s temperature linearly increases along the wall. In the fourth case, the left-hand and the right-hand walls’ temperatures decrease along the wall, symmetry condition. Hence, four scenarios of natural convection in enclosures were covered. Findings: It has been found that the average Nusselt number of the mentioned cases is less than the average Nusselt number of the uniformly heated and cooled enclosure, which reflects the physics of the problem. The work quantifies the deficiency in the rate of the heat transfer. Interestingly one of the mentioned cases showed two counter-rotating horizontal circulations. Such a flow structure can be considered for passively, highly controlled mechanism for species mixing processes application. Originality/value: Previous works assumed that the vertical boundary is subjected to a constant temperature or to a sinusoidal varying temperature. The subject of the work is to examine the effect of non-uniformly heating and/or cooling vertical boundaries on the rate of heat transfer and flow structure for natural convection in a square enclosure. The temperature either linearly increases or decreases along the vertical coordinate at the boundary. Four scenarios are explored. ]]>
<![CDATA[Thermo-optical properties of porous silica thin films produced by sol-gel method]]> Thu, 22 Oct 2020 13:23:21 +0200 Jaglarz, Janusz; Dulian, Piotr; Karasiński, Paweł
rodzaj: artykuł w czasopiśmie
Abstrakt: In this work, the spectral dispersion of optical constants of porous silica thin films have been presented. To determine the optical properties of porous SiO2 films, the ellipsometer Woolam M − 2000 working in the spectral range 190–1700 nm was applied. The thermo-optical coefficients of porous SiO2 films and thermal thickness dependence in temperature range 25–300°C have been determined. The porous SiO2 layers exhibited low refractive indices. The thermo-optical coefficients of presented samples were negative due to the porous structure of SiO2 films. Moreover, it has been stated that thinness has been independent of temperature. After returning to starting conditions, the refractive indices were closer to starting values which confirmed partial reversibility of the heating and cooling process of porous. The thermal properties of porous silica films have been discussed.]]>
<![CDATA[Effectiveness of protective preparations: impact of vegetable oil additives to recipes]]> Thu, 22 Oct 2020 13:04:57 +0200 Kulawik-Pióro, Agnieszka; Klimaszewska, Emilia; Ogorzałek, Marta; Ruman, Justyna; Rożnawska, Klaudia
rodzaj: artykuł w czasopiśmie
Abstrakt: The aim of the study was to demonstrate the effect of the addition of vegetable oils rich in EFA on the effectiveness of hydrophobic skin protection preparations intended for work in the wet environment. Our research hypothesis assumed that the increase in the concentration of vegetable oils in the formula of protective preparations improves their spreadability on the skin, thus translating into acceptance of the preparations by users, improving their quality of life, strengthening the barrier functions of the skin without reducing the effectiveness of the protective action. The distribution capacity of pure vegetable oils was determined using instrumental analysis and sensory analysis, also TEWL tests were used to evaluate their occlusal properties. For protective preparations based on them, the distribution capacity was tested by in vitro methods as well as in vivo tests and sensory analysis were performed. The effectiveness of the tested preparations was measured by tests concerning absorbability, occlusion capacity and washability in aqueous medium. The results were analyzed and compared, and a correlation matrix was developed to establish the relationship between sensory and instrumental measurements. The effectiveness of the preparations depends on the type of oil (its spreadability and viscosity) and the amount in the formulation.]]>
<![CDATA[Modelling the effects of real-time crowding information in urban public transport systems]]> Thu, 22 Oct 2020 12:45:26 +0200 Drabicki, Arkadiusz; Kucharski, Rafał; Cats, Oded; Szarata, Andrzej
rodzaj: artykuł w czasopiśmie
Abstrakt: Public transport (PT) overcrowding is a notorious problem in urban transport networks. Its negative effects upon travel experience can be potentially addressed by disseminating real-time crowding information (RTCI) to passengers. However, impacts of RTCI provision in urban PT networks remain largely unknown. This study aims to contribute by developing an extended dynamic PT simulation model that enables a thorough analysis of instantaneous RTCI consequences. In the model, RTCI is generated and disseminated across the network, and then utilised in passengers’ sequential en-route choices. A case-study demonstration of the RTCI algorithm on urban PT network model of Kraków (Poland) shows that instantaneous RTCI has the potential to improve passengers’ travel experience, although it is also susceptible to inaccuracy. RTCI provision can yield total travel utility improvements of 3% in typical PM peak-hour, with reduced impacts of the worst overcrowding effects (in terms of denied-boarding and in-vehicle travel disutility in overcrowded conditions) of 30%.]]>
<![CDATA[Low-dimensional model for bike-sharing demand forecasting that explicitly accounts for weather data]]> Thu, 22 Oct 2020 12:41:13 +0200 Cantelmo, Guido; Kucharski, Rafał; Antoniou, Constantinos
rodzaj: artykuł w czasopiśmie
Abstrakt: With the increasing availability of big, transport-related datasets, detailed data-driven mobility analysis is becoming possible. Trips with their origins, destinations, and travel times are now collected in publicly available databases, allowing for detailed demand forecasting with methods exploiting big and accurate data. In this paper, we predict the demand pattern of New York City bikes with a low-dimensional approach utilizing three-level data clustering. We use historical demand data along with temperature and precipitation to first aggregate and then decompose data to obtain meaningful clusters. The core of this approach lies in the proposed clustering technique, which reduces the dimension of the problem and, differently from other machine learning techniques, requires limited assumptions on the model or its parameters. The proposed method allows, for the given temperature and precipitation method, to obtain expected vector of movement (mean number and direction of trips) for each zone. In this paper, we synthesize more than 17 million trips into daily and zonal vectors of movement, which combined with weather data allow forecasting of the trip demand. The method allows us to predict the demand with over 75% accuracy, as shown in series of experiments in which various settings and parameterizations are validated against 25% holdout data.]]>
<![CDATA[The effect of the type and amount of synthetic fibers on the effectiveness of dispersed reinforcement in soil-cements]]> Thu, 22 Oct 2020 12:03:22 +0200 Brasse, Krystian; Tracz, Tomasz; Zdeb, Tomasz
rodzaj: artykuł w czasopiśmie
Abstrakt: The paper deals with mechanical properties of soil-cement composites made with non-cohesive soil and reinforced with dispersed fibers. The research was carried out on the basis of three soil-cement matrices whose compositions varied in terms of the volumetric fraction of cement paste and the water-cement ratio. Two types of polypropylene fibers were used as dispersed reinforcement: single fibrillated-tapes polypropylene fibers (SFPF) and bundles of coiled fibrillated-tapes polypropylene fibers (BCFPF). The fibers varied in terms of their length and mass fraction. The objective of the study was to assess the effect of the addition of fibers to soil-cement composites on their flexural tensile strength and on their behavior in the post-critical state. The studies were carried out after 28 days of curing. Bending tests were carried out to determine post-critical stress values σCMODi, stress values at which the matrix is destroyed (limit of proportionality) σLOP, maximum stress values transferred by the fibers σMOR (modulus of rupture), and total fracture energy Gf,tot as well as compressive strength. The test results obtained, and their analysis, indicate the significant impact of the dispersed reinforcement used on the performance of such composites during bending.]]>
<![CDATA[A coupling of multiscale finite element method and isogeometric analysis]]> Thu, 22 Oct 2020 11:54:38 +0200 Dryzek, M.; Cecot, W.
rodzaj: artykuł w czasopiśmie
Abstrakt: In this paper, we propose to use modified B-splines spanned on several macroelements as a basis for building the multiscale finite element method (MsFEM) trail functions. The main benefit of our approach is that the calculations of a multiscale function are done in one step on the whole support, in contrast to standard MsFEM shape functions that are evaluated coarse element by element and require a cumbersome gluing. Selected numerical experiments for flow in porous media with periodic and random material properties distributions were performed to test our modified MsFEM with the new basis functions. We found that the method indeed improves standard MsFEM for fast oscillating material properties. We observed that the resonance effect, when the ratio of inclusion size and coarse mesh size approaches 1 (ε/H → 1) can be reduced by increasing the order of B-splines. ]]>
<![CDATA[Konsystencja jako parametr jakości hydrofobowych preparatów przeznaczonych do ochrony skóry]]> Wed, 21 Oct 2020 14:26:44 +0200 Kulawik-Pióro, Agnieszka; Gibas, Kinga; Osak, Emilia
rodzaj: artykuł w czasopiśmie
Abstrakt: Wprowadzenie. Hydrofobowe środki ochrony skóry oprócz skuteczności w zabezpieczaniu skóry przed niekorzystnymi skutkami pracy w tzw. środowisku mokrym, muszą spełniać odpowiednie kryteria konsumenckie aby być atrakcyjnym na rynku zbytu. Ze względu na swoje przeznaczenie bogate są one w składniki tłuszczowe o wysokich temperaturach wrzenia lub dużej lepkości, przez co trudno się rozprowadzają na skórze i mają ciężką konsystencję. Cel. W pracy podjęto próbę oceny jakości hydrofobowych preparatów ochronnych stosując jako kryterium ich konsystencję oraz zdolność okluzji. Materiał i metody. Badaniu poddano preparaty rynkowe typu emulsji i maści oraz wybrane podłoża maściowe. Stosując metody instrumentalne określono ich zdolność rozprowadzania, wyznaczono krzywe płynięcia, granicę płynięcia, lepkość oraz stopień przepuszczalności pary wodnej. Uzyskane wyniki porównano z wynikami testu probantów. Wyniki. Przeprowadzone badania doświadczalne wykazały, że bardzo ważnym parametrem określającym jakość produktów hydrofobowych do ochrony skóry jest ich konsystencja. Zbyt twarda, będzie sprawiać trudności podczas wyciskania z opakowania i rozprowadzania na skórze, a zbyt miękka może nie utworzyć trwałej bariery mechanicznej na skórze. Jest także cecha decydującą o upodobaniu konsumentów. Miękka konsystencja ułatwia rozprowadzanie środków ochrony na skórze, powodując szybkie wchłanianie kosmetyku bez niekorzystnego wrażenia tłustości i kleistości. Wnioski. Konsystencja wpływa na zdolności ochronne preparatu, na systematyczność jego stosowania oraz na atrakcyjność dla potencjalnego konsumenta - jest jednym z wyznaczników jakości hydrofobowych preparatów ochronnych. Badając konsystencję produktów można tak zaprojektować recepturę aby nie było powodu do wyboru pomiędzy działaniem kosmetyku a przyjemnością jego stosowania.]]>
<![CDATA[Geopolymer composites reinforced with plastic wastes]]> Wed, 21 Oct 2020 14:23:35 +0200 Korniejenko, K.; Mikuła, J.; Łach, M.; Moure Alassio, F.; Moreira Garmendia, L.; Duarte Guigou, M.
rodzaj: artykuł w czasopiśmie
]]>
<![CDATA[The Discontinuous Petrov-Galerkin methodology for the mixed Multiscale Finite Element Method]]> Wed, 21 Oct 2020 13:34:41 +0200 Cecot, Witold; Oleksy, Marta
rodzaj: artykuł w czasopiśmie
Abstrakt: We present the application of the Discontinuous Petrov–Galerkin (DPG) methodology for the mixed Multiscale Finite Element Method (MsFEM). The MsFEM upscaling technique relies on incorporating fine-scale features through special, in a sense optimized for approximability, trial functions while the DPG methodology allows for the selection of the optimal test functions to provide stability of the FEM approximation. The special trial functions are computed online by the solution of local boundary value problems. We improved this process using the static condensation that restricted the construction of the functions to the coarse mesh skeleton (element interfaces) only. We have verified by numerical tests that the proposed improvement of MsFEM reduced both the approximation error and computational cost. Moreover, it simplified the algorithm significantly. The key component of this prolongation construction is our novel method for prolongation of both traction and displacement vectors on element edges of arbitrary shape. The proposed prolongation operator may be also used in the multigrid solver for direct analysis of composites with varying material parameters, using an arbitrary well-posed functional setting with or without the DPG methodology.]]>
<![CDATA[Historic building thermal diagnostics algorithm presented for the example of a townhouse in Lviv]]> Wed, 21 Oct 2020 12:44:42 +0200 Orlik-Kożdoń, Bożena; Radziszewska-Zielina, Elżbieta; Fedorczak-Cisak, Małgorzata; Steidl, Tomasz; Białkiewicz, Andrzej; Żychowska, Maria ; Muzychak, Andriy
rodzaj: artykuł w czasopiśmie
Abstrakt: This paper presents a proposal for a historic building thermal diagnostics algorithm for the example of a historical townhouse located in Lviv, Ukraine. The authors proposed a testing and diagnostics procedure that should precede design and renovation work associated with improving the energy standard of the buildings under discussion. The procedure was presented using a case study of a selected historical building. The scope of the study included an assessment of the building’s technical condition, thermal vision diagnostics, wall moisture, and water absorption in the context of protection against rain. Sample thermal and hygrothermal calculations were performed for a sample architecture element. The calculations included simulations of partition envelope behaviour after planned thermal retrofitting had been carried out. Performing the presented thermal diagnostics methods in three interlinked blocks (A, B, and C) shall ensure the proper thermal retrofitting of historical buildings in the context of their further occupancy.]]>
<![CDATA[Improvements of working parameters in an opposed piston CI two-stroke engine by modelling research]]> Tue, 20 Oct 2020 12:32:44 +0200 Mitianiec, Władysław
rodzaj: artykuł w czasopiśmie
Abstrakt: The opposed piston two-stroke engines (OPE) have very high potential for industrial applications by the simple design, technology and also by high efficiency, particularly with turbo-charging system. The paper presents possibilities of change working parameters of two-stroke diesel engine with opposed pistons by changing geometrical parameters and boosting parameters. Obtaining of higher engine efficiency is realized by change of the crank phase shift of the exhaust piston in relation to the transfer piston. It was assumed that only the piston of the exhaust cylinder changes its position relative to the piston in the cylinder with transfer ports. Modification of scavenging process by changing pistons' position connecting with two crankshafts enables an asymmetrical scavenging timing. Decreasing earlier closing of exhaust ports before compression process and longer time of emptying the cylinder from exhaust gases gives higher engine work and with high boost ratio increases engine power. This type of engine is recently recommended for power plant stations. The paper includes mathematical model of thermodynamic parameters of opposed CI two-stroke engine and full analysis of engine work with scavenge and combustion processes for different timing phases based on geometry of the CI Leyland L60 engine by using own 0D computer program taking into account unsteady gas flow and also CFD modelling. Simulation tests indicate a high scavenge efficiency, good penetration of injected fuel and fast combustion process. The work contains figures of pressure, temperature traces and emission of main chemical species in exhaust gases with comparison of engine works for different timing phases. Applying of non-symmetrical scavenging process in the two-stroke OPE by earlier closing of the exhaust ports increases working parameters. Despite shorter expansion time the expansion work of this engine is bigger at earlier exhaust port opening than at later opening. Two-stroke OPE with earlier opening of exhaust ports enable decreasing of NOx due to lower combustion temperature. The study is an input for realization of such processes in a future of power plant engines with different fuelling systems.]]>
<![CDATA[Transverse shear effects in supersonic flutter problems for composite multilayered rectangular plates - Benchmark for numerical analysis]]> Tue, 20 Oct 2020 12:31:45 +0200 Muc, Aleksander
rodzaj: artykuł w czasopiśmie
Abstrakt: To investigate the influence of transverse shear effects the present paper demonstrates the comparison of flutter characteristics for rectangular multilayered composite plates. The concise variational formulation is shown for various variants of the plate theories (classical, first order and higher order). The analytical, closed form solution is found for a specific boundary conditions dealing with two opposite edges being simply supported. The evaluated method of solution can be treated as the benchmark for numerical analysis since analytical results can be obtained directly with the use of the symbolic packages, such as Mathematica, Maple or Matlab.]]>
<![CDATA[Efekty i możliwości termomodernizacji bryły zabytkowego, murowanego kościoła]]> Tue, 20 Oct 2020 11:28:51 +0200 Machowska, Dorota
rodzaj: artykuł w czasopiśmie
Abstrakt: W artykule przedstawiono, w jakim stopniu wykonanie dozwolonych przez konserwatora prac związanych z ociepleniem bryły zabytkowego, murowanego kościoła spowoduje zmniejszenie rocznego zużycia energii na cele grzewcze oraz ograniczy występowania w kościele różnych, niekorzystnych zjawisk związanych z przepływem ciepła i wentylacją. Analizowano również, o ile po termomodernizacji może zmniejszyć się zużycie paliwa tj. gazu lub węgla na cele grzewcze i tym samym emisja CO2 do atmosfery. Porównano efekty takiej termomodernizacji, przy stałym i okresowym sposobie ogrzewania kościoła oraz gdyby był on zlokalizowany w różnych miastach Polski. Do analizy przy-jęto bryłę zabytkowego kościoła znajdującego się w gminie Zarszyn.]]>
<![CDATA[Steady flow with unilateral and leak/slip boundary conditions by the Stokes variational–hemivariational inequality]]> Tue, 20 Oct 2020 11:06:34 +0200 Migórski, Stanisław; Dudek, Sylwia
rodzaj: artykuł w czasopiśmie
Abstrakt: The stationary Stokes equations for a generalized Newtonian fluid with nonlinear unilateral, and slip and leak boundary conditions are investigated. Boundary conditions include the generalized Clarke gradient and the convex subdifferential, and the variational formulation of the problem is the variational–hemivariational inequality for the velocity field. Existence and uniqueness result for weak solution is proved by using a surjectivity theorem for a pseudomonotone perturbation of a maximal monotone operator.]]>
<![CDATA[Transformed GARMA model: properties and simulations]]> Tue, 20 Oct 2020 10:02:54 +0200 Andrade, Breno Silveira de; Leskow, Jacek; Andrade, Marinho G.
rodzaj: artykuł w czasopiśmie
Abstrakt: Real time series can present anomalies, like non-additivity, nonnormality, and heteroscedasticity, which makes using GARMA models impossible. Our article introduces a new class of models called Transformed Generalized Autoregressive Moving Average (TGARMA) models that allow using transformations to guarantee the GARMA assumptions.We present an extensive simulation study of the influence of the transformation on GARMA estimation. We also propose using bootstrap methods to get more information about the distribution of the transformation parameter. We apply the methodology to data related to annual Swedish fertility rates.]]>
<![CDATA[Application of classifcation neural networks for identifcation of damage stages of degraded low alloy steel based on acoustic emission data analysis]]> Tue, 20 Oct 2020 09:05:47 +0200 Krajewska-Śpiewak, Joanna; Lasota, Igor; Kozub, Barbara
rodzaj: artykuł w czasopiśmie
Abstrakt: The paper presents the infuence of low alloy steel degradation on the acoustic emission (AE) generated during static tension of notched specimen. The material was cut from a technological pipeline long-term operated in the oil refnery industry. Comparative analysis of AE activity generated by damage process of degraded and new material has been carried out. The diferent AE parameters were used to detect diferent stages of fracture process of low alloy steel under quasi-static tensile test. Neural networks with three layers were created with Broyden–Fletcher–Goldfarb–Shanno learning algorithm for a database analysis. The diferent AE parameters were included in the input layer. Classifcation neural networks were created in order to determine the stages of material degradation. The results obtained from the carried out studies will be used as the basis for new methodology development of the assessment of the structural condition of in-service equipment.]]>
<![CDATA[IoT based smart parking system using deep long short memory network]]> Tue, 20 Oct 2020 09:03:31 +0200 Ali, Ghulam; Ali, Tariq; Irfan, Muhammad; Draz, Umar; Sohail, Muhammad; Glowacz, Adam; Sulowicz, Maciej; Mielnik, Ryszard; Bin Faheem, Zaid; Martis, Claudia
rodzaj: artykuł w czasopiśmie
Abstrakt: Traffic congestion is one of the most notable urban transport problems, as it causes high energy consumption and air pollution. Unavailability of free parking spaces is one of the major reasons for traffic jams. Congestion and parking are interrelated because searching for a free parking spot creates additional delays and increase local circulation. In the center of large cities, 10% of the traffic circulation is due to cruising, as drivers nearly spend 20 min searching for free parking space. Therefore, it is necessary to develop a parking space availability prediction system that can inform the drivers in advance about the location-wise, day-wise, and hour-wise occupancy of parking lots. In this paper, we proposed a framework based on a deep long short term memory network to predict the availability of parking space with the integration of Internet of Things (IoT), cloud technology, and sensor networks. We use the Birmingham parking sensors dataset to evaluate the performance of deep long short term memory networks. Three types of experiments are performed to predict the availability of free parking space which is based on location, days of a week, and working hours of a day. The experimental results show that the proposed model outperforms the state-of-the-art prediction models.]]>
<![CDATA[Application of Lyapunov's methods for analyzing the stability of a tubular chemical reactor with recycle]]> Tue, 20 Oct 2020 08:25:54 +0200 Berezowski, Marek
rodzaj: artykuł w czasopiśmie
Abstrakt: First and second Lyapunov's method were adapted here to analyze the stability of a tubular chemical reactor with recycle. The criterion of local stability, in the form of inequalities, was derived using Lyapunov's first method. It is an explicit algebraic form, despite the fact that the mathematical model of the reactor is a partial differential problem with an boundary condition. As part of the second Lyapunov's method, a mathematical criterion for non‐local stability was derived in the form of an increase of Lyapunov's function. Both criteria are presented on graphs.]]>
<![CDATA[Optimisation of the co-combustion of meat–bone meal and sewage sludge in terms of the quality produced ashes used as substitute of phosphorites]]> Mon, 19 Oct 2020 11:56:11 +0200 Kowalski, Zygmunt; Banach, Marcin; Makara, Agnieszka
rodzaj: artykuł w czasopiśmie
Abstrakt: To obtain a high-quality phosphorus raw material comparable in quality to the best phosphorites used in the fertiliser industry, an analysis was carried out to determine the optimal mass proportions of a meat–bone meal and sewage sludge mixture to be used in a cocombustion process. The ashes obtained contained hydroxyapatite that could be considered a high-quality substitute for phosphorites, with an average P2O5 content of 33.5%. These ashes do not contain fluorine compounds, cadmium content is at trace levels and they do not contain the radioactive compounds that are present in trace amounts in all phosphates. The developed process is an example of a production complex using cleaner technologies and circular economy principles on a microeconomic scale.]]>
<![CDATA[An aplication of functional data analysis to local damage detection]]> Mon, 19 Oct 2020 11:36:07 +0200 Leśkow, Jacek; Skupień, Maria
rodzaj: artykuł w czasopiśmie
Abstrakt: Vibration signals sampled with a high frequency constitute a basic source of information about machine behaviour. Few minutes of signal observations easily translate into several millions of data points to be processed with the purpose of the damage detection. Big dimensionality of data sets creates serious difficulties with detection of frequencies specific for a particular local damage. In view of that, traditional spectral analysis tools like spectrograms should be improved to efficiently identify the frequency bands where the impulsivity is most marked (the so-called informative frequency bands or IFB). We propose the functional approach known in modern time series analysis to overcome these difficulties. We will process data sets as collections of random functions to apply techniques of the functional data analysis. As a result, we will be able to represent massive data sets through few real-valued functions and corresponding parameters, which are the eigenfunctions and eigenvalues of the covariance operator describing the signal. We will also propose a new technique based on the bootstrap resampling to choose the optimal dimension in representing big data sets that we process. Using real data generated by a gearbox and a wheel bearings we will show how these techniques work in practice.]]>
<![CDATA[Time average estimation in the fraction-of-time probability framework]]> Mon, 19 Oct 2020 11:21:31 +0200 Dehay, Dominique; Leśkow, Jacek; Napolitano, Antonio
rodzaj: artykuł w czasopiśmie
Abstrakt: The problem of time average estimation is addressed in the fraction-of-time probability framework. In this approach, the observed signal is modeled as a single function of time rather than as a sample path of a stochastic process. Under mild regularity assumptions on temporal cumulants of the signal, a central limit theorem (CLT) is proved for the normalized error of the time average estimate, where the normal- izing factor is the square root of the observation interval length. This rate of convergence is the same as that obtained in the classical stochastic approach, but is derived here without resorting to mixing assumptions. That is, no ergodicity hypothesis is needed. Examples of functions of interest in communi- cations are provided whose time average estimate satisfies the CLT. For the class of the almost-periodic functions, a non normal limit distribution for the normalized error of the time average estimate can be obtained when the normalizing factor equals the observation interval length. The limit distribution, nev- ertheless, depends on the sequence adopted to perform the limit, a result that cannot be obtained in the classical stochastic approach. Numerical examples illustrate the theoretical results and an application to test the presence of a nonzero-mean cyclostationary signal is presented.]]>
<![CDATA[Correlations of urban sprawl with transport patterns and socioeconomics of university students in Cracow, Poland]]> Mon, 19 Oct 2020 11:05:05 +0200 Mehriar, Melika; Masoumi, Houshmand; Nosal-Hoy, Katarzyna
rodzaj: artykuł w czasopiśmie
Abstrakt: Urban sprawl is considered as a western urban development pattern, which is common in different cities around the world. Although, a large number of studies have focused on urban sprawl, modelling urban sprawl has been less emphasised, especially in various geographical contexts. This study aims to investigate urban sprawl and its determinants in a post-socialist country and model urban sprawl based on disaggregated data. In addition, the correlations of urban sprawl with travel patterns were examined, along with the socioeconomic characteristics of university students in Cracow, Poland by applying the Weighted Least Square (WLS) regression model. The WLS regression model was fitted based on the data from 1,288 online questionnaires targeting university students. Furthermore, urban sprawl around the home and the university for each student who indicated the nearest intersection to their home and university were separately estimated by employing the Shannon entropy. Based on the findings, urban sprawl around homes was correlated with 14 transport patterns and socioeconomic features such as gender, age, driving license, financial dependency status, gross monthly income, number of commute trips, mode of transportation for commuting, number of trips for shopping or entertainment, daily shopping area, mode choice for shopping and entertainment trips inside and outside the neighbourhoods, frequency of public transport use, the attractiveness of shops inside the neighbourhoods, and the length of time living in the current home. Additionally, urban sprawl around the university was significantly correlated with age, car ownership, number of commute trips, and a sense of belonging to neighbourhoods, entertainment place, and residential location choice. Finally, a positive correlation was reported between urban sprawl with higher income, elderly student, financial dependent students, and car dependency trips, while urban sprawl was negatively related to the use of public transit.]]>
<![CDATA[Structural studies (FTIR, XRD) of sodium carboxymethyl cellulose modified bentonite]]> Mon, 19 Oct 2020 10:00:12 +0200 Cukrowicz, S.; Grabowska, B.; Kaczmarska, K.; Bobrowski, A.; Sitarz, M.; Tyliszczak, B.
rodzaj: artykuł w czasopiśmie
Abstrakt: The study investigates the effect of the organic compound representing the cellulose derivative - sodium salt of carboxymethyl cellulose (CMC/Na) on the structure of the main component of bentonite (B) - montmorillonite (MMT). Structural analysis revealed that the CMC/Na of different viscosity interacts with the mineral only via surface adsorption, causing at the same time partial or full delamination of its layered structure. This was confirmed by the XRD diffraction tests. Such polymer destructive influence on the structure of the modified main component of the bentonite limits the use of its composites as an independent binder in moulding sand technology, but does not exclude it from acting as an additive being a lustrous carbon carrier. According to the IR spectra of the B/CMC/Na materials, it can be stated that the interaction between the organic and inorganic parts is based on the formation of hydrogen bonds. That kind of the interpretation applies especially to the MMT modified in the bentonite with a lower viscosity polymer. The characteristics of the main IR absorption bands for composites with a higher viscosity polymer indicates the formation of less stable structures suggesting the random nature of the hydrogen bonds formation.]]>
<![CDATA[Long-term performance of anti-freeze protection system of a solar thermal system]]> Mon, 19 Oct 2020 08:57:01 +0200 Pater, Sebastian
rodzaj: artykuł w czasopiśmie
Abstrakt: In a moderate, transitory climate, to prevent freezing of outdoor pipes and collectors in solar thermal systems, anti-freezing fluids are commonly used. There is little experience of using water without any additives as a solar thermal fluid in such a climate. Based on these findings, to fill the knowledge gap this article presents the long-term results of thermal performance and anti-freeze protection of a solar heating system with heat pipe evacuated tube collectors with water as a solar thermal fluid. The operation of this system under real conditions was analysed for five years in southern Poland. The annual value of solar insolation ranged from 839 to almost 1000 kWh/m2. The monthly efficiency of the solar collectors from March to October was usually higher than 25%, and the lowest was between November and January. The anti-freeze protection system consumed annually from 7 to 13% of the heat generated by the collectors in the installation. Supporting the operation of the central heating system in the building during the winter season highly improved the efficiency of the solar collectors. Results show that it is possible to use water without any additives as a solar thermal fluid in a moderate, transitory climate.]]>
<![CDATA[Aminotriazines with indole motif as novel, 5-HT7 receptor ligands with atypical binding mode]]> Mon, 19 Oct 2020 08:45:17 +0200 Kułaga, Damian; Jaśkowska, Jolanta; Satała, Grzegorz; Latacz, Gniewomir; Śliwa, Paweł
rodzaj: artykuł w czasopiśmie
Abstrakt: Developing new and selective 5-HT7R ligands may have a key impact on the treatment of central nervous system diseases including depression. We have found that indoleaminotriazine core fused with alkyl aryl moiety exhibits high affinity and selectivity to 5-HT7R. SAR analysis demonstrated that the ethyl or ethoxy group (5c 5-HT7R Ki = 8 nM; 5d 5-HT7R Ki = 55 nM) is the optimal carbon linker between triazine and aryl moiety. The results of the molecular dynamics simulations show stable interaction with E7.34 upon binding to a 5-HT7R. Compounds 5c and 5d were tested for early ADMET parameters. Compounds are not hepatotoxic and exhibit moderate potential interaction with other drugs metabolized by CYP3A4 or CYP2D6. ]]>
<![CDATA[Recognition of species and genera of bacteria by means of the product of weights of the classifiers]]> Fri, 16 Oct 2020 12:05:02 +0200 Plichta, Anna
rodzaj: artykuł w czasopiśmie
Abstrakt: In microbiology, computer methods are applied in the analysis and recognition of laboratory-acquired microscopic images concerning, for example, bacterial cells or other microorganisms. Proper recognition of the species and genera of bacteria is a key stage in the microbiological diagnostics process, because it allows a quick start of the appropriate therapy. The original method proposed in the paper concerns the automatic recognition of selected species and genera of bacteria presented in digital images. The classification was made on the basis of the analysis of the physical characteristics of bacterial cells using the product of classifier confidence weights. The end result of the classification process is the classification list, sorted in descending order according to the weights of the classifiers. In addition to the correct classification, a list of other possible results of the analysis is obtained. The method thus allows not only the classification, but also an analysis of the confidence level of the selection made. The proposed method can be used to recognize not only bacterial cells, but also other microorganisms, for example, fungi that exhibit similar morphological characteristics. In addition, the use of the method does not require the application of specialized computer equipment, which widens the scope of applications regardless of the laboratory IT infrastructure, not only in microbiological diagnostics, but also in other diagnostic laboratories.]]>
<![CDATA[Ordered fuzzy random variables: Definition and the concept of normality]]> Fri, 16 Oct 2020 11:29:47 +0200 Marszałek, Adam; Burczyński, Tadeusz
rodzaj: artykuł w czasopiśmie
Abstrakt: The concept of fuzzy random variable combines two sources of uncertainty: randomness and fuzziness, whereas the model of ordered fuzzy numbers provides a representation of inaccurate quantitative data, and is an alternative to the standard fuzzy numbers model proposed by Zadeh. This paper develops the model of ordered fuzzy numbers by defining the concept of fuzzy random variables for these numbers, called further ordered fuzzy random variables. Thanks to the well-defined arithmetic of ordered fuzzy numbers (existence of neutral and opposite elements) and the introduced ordered fuzzy random variables; it becomes possible to construct fully fuzzy stochastic time series models such as e.g., the autoregressive model or the GARCH model in the form of classical equations, which can be estimated using the least-squares or the maximum likelihood method. Furthermore, the concept of normality of ordered fuzzy random variables and the method to generate pseudo-random ordered fuzzy variables with normal distribution are introduced.]]>
<![CDATA[Avant-garde and contemporary architecture]]> Fri, 16 Oct 2020 11:02:50 +0200 Kozłowski, Tomasz
rodzaj: artykuł w czasopiśmie
Abstrakt: The text attempts to present contemporary architecture with its commercial connotations against the background of the aspirations of the early 20th century avant-garde artists. After years of modernist order, the shapes of architecture have exploded anew and those forgotten for years or known only from drawings have become important again. However, the perception of architecture and its social overtone have changed. The commercial and advertising value of art is nowadays the most important. The artists’ thought of the past can be perceived today as continuity of architecture, although similar, it is already different]]>
<![CDATA[Vectorized mathematical model of a slip-ring induction motor]]> Fri, 16 Oct 2020 10:19:05 +0200 Wcislik, Miroslaw; Suchenia, Karol; Cyganik, Andrzej
rodzaj: artykuł w czasopiśmie
Abstrakt: The paper deals with the modeling of a slip-ring induction motor. Induction motors are very often used in industry and their suitable model is needed to reduce control and operating costs. The identification process of self and mutual inductances of the stator and rotor, and mutual inductances between them in the function of the rotor rotation angle is presented. The dependence of each inductance on the rotor rotation angle is determined experimentally. The inductance matrix is then formulated. Taking the magnetic energy of the inductances and kinetic energy of the rotor into account, the Lagrange function is defined. Next, the motor motion equations are obtained. After making some algebraic transformations and using the dimensionless variables, the motion equations of electric circuits and of the mechanical equation are written separately in the forms facilitating their solution. The solution was obtained using the Simulink model for the stator and rotor currents in the form of vectors. The simulation was controlled by MATLAB script. The results of the simulation are presented in the form of basic variables time courses and compared with some values calculated with the use Steinmetz model of induction motor. The work is followed by two appendices, which contain procedures for determining the inverted inductance matrix.]]>
<![CDATA[Assessment of changes in channel morphology in a mountain river regulated using grade control structures]]> Thu, 15 Oct 2020 13:41:30 +0200 Korpak, Joanna
rodzaj: artykuł w czasopiśmie
Abstrakt: Grade control structures (GCSs) serve as some of the most frequently used forms of river channel regulation in the Polish Carpathians. The main purpose of such structures is to reduce the gradient of the channel and strike a balance between erosion and deposition. Despite the widespread use of GCSs, not much is known about their functioning over the long term. The aim of the study was to examine a host of changes in channel morphology in a mountain river regulated using such structures. The object of the research was the lower stretch of Biały Dunajec – a Carpathian river that follows a high mountain regime. The studied river stretch was regulated 33 years ago. The history of regulation and state of the channel immediately following regulation work were assessed using available regulation documents as well as a document on the post-construction period for the studied structures. The presentday morphology of the studied river channel was investigated via a geomorphologic survey and assessment of 22 channel cross sections. Gradual changes in morphology were analyzed using orthophotomaps from different years. Research has shown that the studied river channel is shaped by all fluvial processes. In the longitudinal profile, distinct channel zones characterized by stable tendencies were identified. The upstream zone is dominated by deposition, where the channel is flooded with debris after each high water stage, and GCSs cease to function as barriers to material transport. In the middle zone, lateral erosion plays a greater role, while in the downstream zone it is downcutting and lateral erosion. The river cuts alternately into both banks, thus damaging its regulated pathway. The role of deposition increases once again in the mouth zone of the river. The studied channel is not stable, and its morphology has changed many times over the years due to discharges much lower than design discharge. The Biały Dunajec did not conform to the parameters of its regulated pathway and aims to increase its width and sinuosity. The studied channel stretch requires ongoing financial expenditures to cover repair work. ]]>
<![CDATA[Solving topology optimization problems using cellular automata and mortar finite element method]]> Thu, 15 Oct 2020 12:27:42 +0200 Yashchuk Yu. O.; Tajs-Zielinska, Katarzyna
rodzaj: artykuł w czasopiśmie
Abstrakt: Currently topology optimization is widely used by engineers for different practical problems. Researches by different authors offer algorithms of using cellular automata in these problems, and most recent publications introduce a mesh-refinement procedure to decrease numerical efforts. In this article, we propose to apply a mortar finite element method for solving topology optimization problems using cellular automata. This methodology enables us to handle the non-conforming meshes, which can arise in the refinement process. We present a formulation of the algorithm and analyse its computational complexity by applying to a test problem.]]>
<![CDATA[Determination of catastrophic sets of a tubular chemical reactor by two-parameter continuation method]]> Thu, 15 Oct 2020 12:13:58 +0200 Berezowski, Marek
rodzaj: artykuł w czasopiśmie
Abstrakt: The work relates to development and presentation a two-parameter continuation method for determining catastrophic sets of stationary states of a tubular chemical reactor with mass recycle. The catastrophic set is a set of extreme points occurring in the bifurcation diagrams of the reactor. There are many large IT systems that use the parametric continuation method. The most popular is AUTO’97. However, its use is sometimes not convenient. The method developed in this work allows to eliminate the necessity to use huge IT systems from the calculations. Unlike these systems, it can be inserted into the program as a short subroutine. In addition, this method eliminates time-consuming iterations from the calculations.]]>
<![CDATA[Tests on the mechanical properties of polymers in the aspect of an attempt to determine the parameters of the Mooney-Rivlin hyperelastic model]]> Thu, 15 Oct 2020 12:03:11 +0200 Śliwa-Wieczorek, Klaudia; Zając, Bogusław; Kozik, Tomasz
rodzaj: artykuł w czasopiśmie
Abstrakt: The article presents testing of the mechanical properties of SIKA® polymer adhesives of the type PBM, PMM, PM, and PSM in the aspect of an attempt to determine the parameters of the Mooney-Rivlin hyperelastic model. The article contains a literature review on developed models for hyperelastic materials as well as a description of the author’s own results obtained in monaxial tensile and monaxial compression tests conducted on oars and cylindrical samples, respectively. Furthermore, the results of modeling of Mooney-Rivlin hyperelastic model parameters are shown in relation to the value of average parameters for polymers after both a week and a month-and-a-half of ripening.]]>
<![CDATA[The recovery of rare-earth metals from fly ash using alkali pre-treatment with sodium hydroxide]]> Thu, 15 Oct 2020 11:36:31 +0200 Żelazny, Sylwester; Świnder, Henryk; Jarosiński, Andrzej; Białecka, Barbara
rodzaj: artykuł w czasopiśmie
Abstrakt: The aim of the work was to draw attention to the usefulness of the alkaline thermal activation process with sodium hydroxide in the process of rare earth metal leaching (REE), from fly ash with hydrochloric acid and nitric acid(V). The work is a part of the authors’ own research aimed at optimizing the REE recovery process coming from fly ash from hard coal combustion. The article contains an assessment of the possibility of leaching rare earth metals (REE) from fly ash originating from the combustion of hard coal in one of the Polish power plants. The process was carried out for various samples consisting of fly ash and sodium hydroxide and for different temperatures and reaction times. The process was carried out for samples consisting of fly ash and sodium hydroxide containing respectively 10, 20 and 30% on NaOH by weight in relation to the weight of fly ash. Homogenization of these mixtures was carried out wet, and then they were baked at 408K, 433K and 473K, for a period of three hours. The mixture thus obtained was ground to a particle size of less than 0.1 mm and washed with hot water to remove excessive NaOH. The solid post-reaction residue was digested in concentrated HCl at 373K for 1 hour at a weight ratio fs/fc of 1:10. The results of chemical analysis and scanning microscopic analysis along with EDS analysis and X-ray analysis were used to characterize the physicochemical properties of the tested material. The results indicated that REE recovery from fly ash strictly depends on heat treatment temperature with NaOH, and an increase in REE recovery from alkaline-activated fly ash along with increa- sing the amount of NaOH in relation to fly ash mass.]]>
<![CDATA[Impact of the geometrical parameters of dolomite coarse aggregate on the thermal and mechanic properties of preplaced aggregate concrete]]> Thu, 15 Oct 2020 11:29:49 +0200 Stempkowska, Agata; Gawenda, Tomasz; Naziemiec, Zdzisław; Ostrowski, Krzysztof Adam; Saramak, Daniel; Surowiak, Agnieszka
rodzaj: artykuł w czasopiśmie
Abstrakt: The article shows investigations on the behavior of preplaced aggregate concrete with regular and irregular coarse aggregates. The thermal properties, compressive strength, and internal structure were analyzed based on computed tomography images. The regular and irregular shapes of aggregates were obtained according to patented technology, which is possible to produce in both laboratory and industrial conditions. Based on the conducted calculations, heat storage capacity was assessed. The influence of grain shape on the material strength, porosity, and hydration gaps was determined. Debonded porosity, as a result of aggregate impurities, was shown using computer tomography analysis. It was shown that the arrangement and shape of the grains has a significant impact on the performance properties of hardened preplaced concrete.]]>
<![CDATA[Hydromorphological index for rivers: a new method for hydromorphological assessment and classification for flowing waters in Poland]]> Thu, 15 Oct 2020 11:15:01 +0200 Szoszkiewicz, Krzysztof; Radecki-Pawlik, Artur
rodzaj: artykuł w czasopiśmie
Abstrakt: The method based on original metric called Hydromorphological Index for Rivers (HIR) was developed in 2017 for the purpose of the monitoring of the hydromorphological status of flowing waters in Poland. It fulfils the requirements of the EU Water Framework Directive (WFD). It allows the assessment of both lowland rivers as well as mid-altitude and highland streams. The proposed system can be used to assess the natural and heavily modified rivers as well as artificial channels. The basis of the proposed system is a field survey, which is supplemented by the analysis of Geographic Information Systems (GIS) data and remote sensing materials. The analysis of the GIS data and remote sensing materials already enable to estimate preliminary classification of the hydromorphological status of the non-surveyed water bodies. On the basis of the field survey, the principal HIR value can be estimated for the considered river site and comparing with the reference conditions, the hydromorphological quality status in the five-class system can be calculated. The properly selected, representative survey sites (one or more depending on the heterogeneity of the environment), enable the classification and evaluation of entire surface water bodies in the framework of the national environmental monitoring. The GIS component of the HIR proved to be useful in verifying the determination of heavily modified water bodies and in assessing the needs of river restoration. It was also applied in the development of the National river restoration program for predicting the impact of the proposed restoration measure on the state of hydromorphology.]]>
<![CDATA[Development of cost estimation models based on ann ensebles and the SVM method]]> Thu, 15 Oct 2020 10:04:41 +0200 Juszczyk, Michał
rodzaj: artykuł w czasopiśmie
Abstrakt: Cost estimation, as one of the key processes in construction projects, provides the basis for a number of project-related decisions. This paper presents some results of studies on the application of artificial intelligence and machine learning in cost estimation. The research developed three original models based either on ensembles of neural networks or on support vector machines for the cost prediction of the floor structural frames of buildings. According to the criteria of general metrics (RMSE, MAPE), the three models demonstrate similar predictive performance. MAPE values computed for the training and testing of the three developed models range between 5% and 6%. The accuracy of cost predictions given by the three developed models is acceptable for the cost estimates of the floor structural frames of buildings in the early design stage of the construction project. Analysis of error distribution revealed a degree of superiority for the model based on support vector machines. ]]>
<![CDATA[Comprehensive analysis of preparation strategies for phase change nanocomposites and nanofluids with brief overview of safety equipment]]> Thu, 15 Oct 2020 10:03:48 +0200 Jurčević, Mišo ; Nižetić, Sandro ; Arıcı, Müslüm; Ocłoń, Paweł
rodzaj: artykuł w czasopiśmie
Abstrakt: The preparation process of the nanocomposites and nanofluids strongly affects their general physical properties and stability in general. They are very sensitive with respect to the quality of the preparation process which should be obtained carefully to produce quality and reliable homogeneous samples. This paper provides a useful analysis in different preparation procedures with the focus on the nano-enhanced phase change materials (NEPCM) and fluids (nanofluids) due to their wide application areas. The preparation processes were identified and categorized together with the key parameters that have an important impact on the preparation process in general. The main problems and issues during the preparation process were discussed and elaborated in detail, gained by a detailed analysis of commonly applied preparation procedures. Since the preparation process of both nanofluids and nanocomposites should be carefully planned regarding the working safety, an overview of the safety equipment was provided as well as an assessment of the toxic potential of nanomaterials. Quality and well obtained preparation process can contribute to the rational utilization of the nanomaterials, and by that, it could reduce negative environmental footprints released from production as well as application of the nanomaterials. The main research findings of this paper provide useful guidelines for researchers dealing with the preparation of nano-enhanced fluids and phase change materials that should be helpful to get insights directed to the complexity of the preparation process and ensure an efficient preparation process.]]>
<![CDATA[Preparation of titanium oxide-based nanoparticles modified with D-(+)-mannose and investigation of their properties as a potential drug carrier]]> Thu, 15 Oct 2020 09:45:20 +0200 Pulit-Prociak, Jolanta; Staroń, Anita; Długosz, Olga; Kluz, Klaudia; Banach, Marcin
rodzaj: artykuł w czasopiśmie
Abstrakt: Titanium oxide nanoparticles modified with D-(?)-mannose were obtained. In the process of their formation, they were conjugated with an active substance (tadalafil). The physicochemical properties of the obtained products were assessed, and the size and electrokinetic potential were determined using a dynamic light scattering technique. X-ray diffractometry was applied in order to define the crystalline properties, and Fourier-transform infrared spectroscopy was used to confirm the formation of the desired products. It was possible to obtain TiO2 coated with D-(?)-mannose. The average size of nanoparticles was between 230 and 268 nm. The release of the active substance from the product over a time period of three hours was assessed against the reference material, which was not modified by D-(?)-mannose. The results indicate that covering titanium oxide nanoparticles with the modifying substance favours a slower rate of release for the active substance, which is the desired effect from a pharmacological point of view. The releasing of active substance from modified products was even 68% slower than that from the reference product. These modified titanium oxides are promising materials that may have found an application as drug carriers.]]>
<![CDATA[3D printing in heterogeneous catalysis – the state of the art]]> Thu, 15 Oct 2020 09:19:08 +0200 Bogdan, Elżbieta; Michorczyk, Piotr
rodzaj: artykuł w czasopiśmie
Abstrakt: This paper describes the process of additive manufacturing and a selection of three-dimensional (3D) printing methods which have applications in chemical synthesis, specifically for the production of monolithic catalysts. A review was conducted on reference literature for 3D printing applications in the field of catalysis. It was proven that 3D printing is a promising production method for catalysts.]]>
<![CDATA[Identification and determination of betacyanins in fruit extracts of melocactus species]]> Thu, 15 Oct 2020 09:02:29 +0200 Sutor, Katarzyna; Wybraniec, Sławomir
rodzaj: artykuł w czasopiśmie
Abstrakt: Betacyanin pigments were studied in edible fruits of four Melocactus species, M. violaceus Pfeiff., M. bahiensis (Britton & Rose) Luetzelb, M. amoenus (Hoffm.) Pfeiff., and M. curvispinus Pfeiff., by means of chromatographic and mass spectrometric techniques. The main pigment constituent, melocactin, endogenously present in the Melocactus species, was identified as betanidin 5-O-β-sophoroside betacyanin, previously known as “bougainvillein-r-I”. The highest total concentration of betacyanins was found in fruits of M. amoenus (∼0.08 mg/g). Except for melocactin being the most abundant betacyanin (34.8–38.8%) in the analyzed species, a presence of its malonylated derivative, mammillarinin (15.2–19.9%), as well as more hydrophobic feruloyled and sinapoyled melocactins was confirmed by additional co-chromatographic experiments with authentic reference betacyanins. The acyl migration isomers of the malonylated betacyanins as well as a presence of 5′′-O-E-sinapoyl-2′-O-apiosyl-betanin (2.3–3.0%) found frequently in light-stressed cacti was also acknowledged.]]>
<![CDATA[Analysis of entropy generation rate during non-adiabatic ice slurry flow in pipes]]> Wed, 14 Oct 2020 13:50:05 +0200 Niezgoda-Żelasko, Beata
rodzaj: artykuł w czasopiśmie
Abstrakt: The paper focuses on the entropy generation rate minimization during the flow of ethanol-based ice slurry through straight pipes with a circular and rectangular cross-section. The authors’ original equations for calculating ice slurry flow resistances and heat transfer coefficients were used to determine the impact of the mass fraction of ice, ice slurry flow velocity and heat flux density on the entropy generation rate values observed during flow through pipes. A dimensionless relationship was proposed to determine the interdependency between flow velocity and mass share of ice for which the entropy values were at the minimum level.The parameter areas in which the entropy flux was minimal were related for different cross-sections of the transverse flow to the areas of parameters xsand w in which the values of overall enhancement efficiency were higherthan one. Thus, a method for verifying the parameters of slurry velocity and mass fraction selected in the design process according to two different criteria was proposed.]]>
<![CDATA[Protective properties of a multi-layer external coating applied to underground pipes of ductile iron]]> Wed, 14 Oct 2020 13:27:52 +0200 Kochmańska, Agnieszka; Wassilkowska, Anna; Dąbrowski, Wojciech
rodzaj: artykuł w czasopiśmie
Abstrakt: In this work the analysis of corrosion for ductile iron pipes with diameters of 350 and 500 mm was performed. Two phenomena regarding the pipes coating deterioration have been recognized: corrosion and abrasion. The corrosion tests performed on different coatings in a neutral salt spray for up to 1000 hours indicate that this method is applicable for a rough external surface of centrifugally casted ductile iron pipes. The abrasion tests have been performed manually, using a grinding paper 1000#, due to an irregular profile of the external pipe surface transferred from the casting mold. It helped to obtain “spotted” sections, which were further microscopically analyzed (layer-by-layer). The last procedure, however not standardized, could be in some regards more convenient comparing to traditional cross-sections.]]>
<![CDATA[Design optimization of heat exchangers with advanced optimization techniques: a review]]> Wed, 14 Oct 2020 13:05:50 +0200 Venkata Rao, R.; Saroj, Ankit; Ocłoń, Paweł; Taler, Jan
rodzaj: artykuł w czasopiśmie
Abstrakt: This literature review presents the extensive literature survey of various heat exchangers (HEs) for the design optimization using advanced optimization techniques concerning with various aspects. The chief objective of this work is to focus on the parametric design optimization of different types of HEs using advanced optimization algorithms and therefore only the research works associated with advanced optimization techniques are considered. This is the first paper which exclusively summaries the research works concerning with the parameter optimization of HEs using advanced optimization techniques. Various types of HEs considered in this review paper are shell-and-tube HEs, plate-fin HEs, fin-tube HEs and various configurations of HE networks etc. The parametric design optimization of HEs is associated with number of structural and physical parameters having highly complexity. Trial and error method is used in the general design approaches and this becomes tediously and time consuming and not having the guarantee of getting an optimum design. Therefore, for the design of HEs advanced optimization techniques are preferred. The review work on parametric design optimization was not attempted previously by taking into consideration various types of HEs therefore this review paper may turn into the complete information at one place and it may be very useful to the industrial design and successive researchers to choose the direction of their research work in the field of parameter optimization of HEs using advanced optimization algorithm.]]>
<![CDATA[An adaptive multi-team perturbation-guiding Jaya algorithm for optimization and its applications]]> Wed, 14 Oct 2020 12:27:06 +0200 Venkata Rao, R.; Keesari, Hameer Singh; Ocłoń, P.; Taler, Jan
rodzaj: artykuł w czasopiśmie
Abstrakt: This study proposes an adaptive multi-team perturbation-guiding Jaya (AMTPG-Jaya) algorithm which uses multiple teams to explore the search space. The proposed algorithm adapts the number of teams to explore the search space based on the convergence to the optimum. Furthermore, each team uses the same set of the population, and there is a different perturbation or movement equation for each team. As each team has a different perturbation scheme, the set of the moves to new positions by each team is unique. The moving equation of the worst performing team will be updated by the superiority of solutions produced by each team. The superiority of the solutions for each team is calculated based on the fitness value and boundary violations of solutions. The proposed algorithm is examined using computationally expensive constrained optimization problems taken from the CEC-2017 technical report. Computational test results have demonstrated the effectiveness of the AMTPG-Jaya algorithm when compared to the other well-known approaches. Also, a multi-objective optimization is carried out on a solar dish Stirling engine system to find the optimal thermo-economic parameters to maximize dimensionless power and thermal efficiency. The computational results revealed that the AMTPG-Jaya algorithm results are superior to those achieved by the other algorithms presented in this work.]]>
<![CDATA[Process maps with metabolic constraints for bioethanol production by continuous fermentation]]> Wed, 14 Oct 2020 12:15:10 +0200 Ciesielski, Adrian; Grzywacz, Robert
rodzaj: artykuł w czasopiśmie
Abstrakt: This paper presents a method of preparing process maps for the bioethanol production process by continuous fermentation. The proposed method of process map construction is based on the nonlinear analysis of bioreactor steady states and the metabolic interpretation method of the steady state branches. The nonlinear analysis of bioreactor steady states was performed relative to the dilution rate and the mass recirculation coefficient. It revealed the presence of nonlinear phenomena in the system, such as Hopf bifurcation points and limit points. The use of the qualitative interpretation method of bifurcation diagrams allowed the detection of metabolic change points and multiple steady state areas in which the metabolic activity of biomass cells undergoes changes. Taking this information into account together with the determined gradient profile of bioethanol concentrations has made it possible to construct a process map with metabolic constraints.]]>
<![CDATA[Analiza ruchu lotnictwa ogólnego w portach lotniczych Polski Południowej do roku 2015]]> Wed, 14 Oct 2020 11:57:17 +0200 Dyrcz, Jakub; Pashkevich, Anton
rodzaj: artykuł w czasopiśmie
Abstrakt: Lotnictwo ogólne to osobny segment lotnictwa cywilnego, ze względu na rodzaj działalności lotniczej zaliczamy do niego: lotnictwo rekreacyjne i sportowe, lotnictwo biznesowe, prace lotnicze, szkolenia lotnicze. Jest często pomijanym segmentem lotniczym w statystykach. Artykuł dotyczy statystyk lotnictwa ogólnego w portach lotniczych Polski Południowej. Porusza problematykę całego sektora lotnictwa ogólnego – jego charakterystykę oraz cechy determinujące jego wydzielenie. Przedstawia ogólne statystyki sektora, a dopiero po przedstawieniu całego segmentu wykonana została analiza ruchu w wybranych portach lotniczych: Kraków – Balice, Wrocław – Strachowice, Katowice – Pyrzowice i Rzeszów – Jasionka. Dokonano oceny panujących tendencji w tym segmencie oraz określono możliwości rozwoju sektora lotnictwa ogólnego.]]>
<![CDATA[An air terminal device with a changing geometry to improve indoor air quality for VAV ventilation systems]]> Wed, 14 Oct 2020 09:37:35 +0200 Szczepanik-Scislo, Nina; Schnotale, Jacek
rodzaj: artykuł w czasopiśmie
Abstrakt: This study aimed to develop a new concept for an air terminal device for a VAV (variable air volume) ventilation system that would improve overall ventilation efficiency under a varying air supply volume. In VAV systems, air volume is modified according to the thermal load in each ventilated zone. However, lowering the airflow may cause a lack of proper air distribution and lead to the degradation of hygienic conditions. To combat this phenomenon, an air terminal device with an adapting geometry to stabilize the air throw, such that it remains constant despite the changing air volume supplied through the ventilation system, was designed and studied. Simulations that were performed using the RNG k–ε model in the ANSYS Fluent application were later validated on a laboratory stand. The results of the study show that, when using the newly proposed terminal device with an adaptive geometry, it is possible to stabilize the air throw. The thermal comfort parameters such as the PMV (predicted mean vote) and PPD (predicted percentage of dissatisfied) proved that thermal comfort was maintained in a person-occupied area regardless of changing airflow though the ventilation system.]]>
<![CDATA[Natural convection in a differentialy heated enclosure filled with low Prandtl number fluids with modified Lattice Boltzman method]]> Wed, 14 Oct 2020 09:00:44 +0200 Bawazeer, S.; Mohamad, A.A.; Ocłoń, P.
rodzaj: artykuł w czasopiśmie
Abstrakt: The convective motion in a three- and two- dimensional square cavity driven by a temperature gradient is analyzed. The cavity is filled with a low-Prandtl-number (Pr) fluid, typical for liquid metals. The vertical walls have constant but different temperatures, while the horizontal boundaries are adiabatic. Low Prandtl number exhibits strong non-linearity, where the advection term dominates the diffusion term in the momentum equations. Therefore, a Multi-Relaxation-Time, modified Lattice Boltzmann (MRT-LBM) approach is used to overcome the stability of the numerical solutions. Also, by using the mentioned method a wide range of Prandtl numbers, Pr, (0.01–0.5) and a wide range of Rayleigh numbers, Ra, (104 to 108) are investigated. It was found that the flow field exhibits periodic oscillations at the critical Rayleigh numbers, which are dependent on the Prandtl number. The periodic flow becomes aperiodic as the Prandtl number decreases and/or the Rayleigh number decreases. Also, the average Nusselt number are presented and correlated for the investigated range of the controlling parameters. ]]>
<![CDATA[3D numerical simulation of condensation and condensate behaviors on textured structures using lattice Boltzmann method]]> Wed, 14 Oct 2020 08:44:03 +0200 Li, Mingjie; Qu, Jingguo; Ocłoń, Paweł; Wei, Jinjia; Tao, Wenquan
rodzaj: artykuł w czasopiśmie
Abstrakt: Condensation is one of the most widely investigated interface phenomenon in science and engineering. However the three-dimensional (3D) condensate behaviors including the initial nucleation, growth, coalescence, penetration, spreading or expansion on textured surfaces have seldom been clarified comprehensively. In this work, the 3D pseudopotential LB model with a phase change model is employed, and the condensation process on textured structures with homogeneous and inhomogeneous wettability is investigated. It is found that the nucleation position rises to the top of the structure and the nucleation time gets longer with the increase of surface hydrophobicity when condensation occurs on homogeneous textured structure, and the dropwise condensation mode transits into the film condensation. The condensation on structures with inhomogeneous surface wettability at the top, side and bottom of the pillars and structures with hybrid top (namely hydrophilic spots in the center of the top of the hydrophobic pillars) is then investigated. It is concluded that hybrid top of the textured structures can enhance condensation heat transfer, shorten the nucleation time, and at the same time maintain the condensate in the Cassie state for a long time before the condensation mode transition, leading to the best condensation performance.]]>
<![CDATA[Effect of fiber posts on stress distribution of endodontically treated upper premolars: finite element analysis]]> Tue, 13 Oct 2020 13:36:29 +0200 Zarow, Maciej; Vadini, Mirco; Chojnacka-Brożek, Agnieszka; Szczeklik, Katarzyna; Milewski, Grzegorz; Biferi, Virginia; D’Arcangelo, Camillo; De Angelis, Francesco
rodzaj: artykuł w czasopiśmie
Abstrakt: By means of a finite element method (FEM), the present study evaluated the effect of fiber post (FP) placement on the stress distribution occurring in endodontically treated upper first premolars (UFPs) with mesial–occlusal–distal (MOD) nanohybrid composite restorations under subcritical static load. FEM models were created to simulate four different clinical situations involving endodontically treated UFPs with MOD cavities restored with one of the following: composite resin; composite and one FP in the palatal root; composite and one FP in the buccal root; or composite and two FPs. As control, the model of an intact UFP was included. A simulated load of 150 N was applied. Stress distribution was observed on each model surface, on the mid buccal–palatal plane, and on two horizontal planes (at cervical and root-furcation levels); the maximum Von Mises stress values were calculated. All analyses were replicated three times, using the mechanical parameters from three different nanohybrid resin composite restorative materials. In the presence of FPs, the maximum stress values recorded on dentin (in cervical and root-furcation areas) appeared slightly reduced, compared to the endodontically treated tooth restored with no post; in the same areas, the overall Von Mises maps revealed more favorable stress distributions. FPs in maxillary premolars with MOD cavities can lead to a positive redistribution of potentially dangerous stress concentrations away from the cervical and the root-furcation dentin.]]>
<![CDATA[The negative and positive pressure system of natural balanced ventilation]]> Tue, 13 Oct 2020 13:10:47 +0200 Gaczoł, Tomasz
rodzaj: artykuł w czasopiśmie
Abstrakt: This paper discusses the results of research conducted with the Ansys Fluent programme on the air flow through natural ventilation supply and exhaust ducts of rooms located on the ground and upper floor of a building. A scenario with air inflow to a room through an air intake located on the basement floor level was selected for the tests. All simulations were performed for outdoor temperatures of +3,+12, and -15°C (simulations run for an outdoor air temperature of +12°C are discussed in detail). The temperature inside the room is +20°C, i.e. at the minimum temperature level for thermal comfort. The simulations address such issues as the pressure system inside the room and in the exhaust duct, the distribution of air temperature in the room and the vector direction of airflow through the supply and exhaust ducts.]]>
<![CDATA[Chaos predictability in a chemical reactor]]> Tue, 13 Oct 2020 12:42:55 +0200 Berezowski, Marek
rodzaj: artykuł w czasopiśmie
Abstrakt: The dynamics of the tubular chemical reactor with mass recycle was examined. In such a system, temperature and concentrations may oscillate chaotically. This means that state variable values are then unpredictable. In this paper, it has been shown that despite the chaos, the behavior of such a reactor can be predictable. It has been shown that this phenomenon can occur in two cases. The first case concerns intermittent chaos. It has been shown that intermittent outbursts can occur at regular intervals. The second case concerns transient chaos, i.e. a situation when chaos occurs only for a certain period of time, e.g. only during start-up. This phenomenon makes it impossible to predict what will occur in the reactor in the nearest time, but, makes it possible to precisely determine the values of the variables even in the distant future. Both of these phenomena were tested by numerical simulation of the mathematical model of the reactor.]]>
<![CDATA[Basalt textile-reinforced vinylester and epoxy resins for anchors used to fasten ventilated building facades]]> Tue, 13 Oct 2020 11:48:41 +0200 Majka, Tomasz, M.; Byrdy, Aleksander; Pielichowski, Krzysztof
rodzaj: artykuł w czasopiśmie
Abstrakt: The aim of this work was to obtain insulation composite anchors based on basalt textile-reinforced vinylester and epoxy resins for fixing heavy building elevation cladding. It concerns the problem of applying materials not originating from wood, construction steel or concrete in the building industry. So far, the application of polymeric materials, including polymeric composites, in construction has been limited to paints, varnishes and glues, and the use of engineering polymers as building materials has been limited. This article presents a study on the influence of the type of basalt reinforcement (in the form of textile, chopped fibre and powder) on the mechanical and functional properties of vinylester and epoxy compositions towards potential applications as construction anchors to fasten building facades. Based on an analysis of the experimental results, a material was selected for the production of novel construction anchors. The results reported here constitute an introduction to further considerations related to the applications of vinylester resin/basalt and epoxy resin/basalt composites as construction materials alternative to commonly used steel and aluminium.]]>
<![CDATA[Dual hysteresis model of MR dampers]]> Tue, 13 Oct 2020 11:45:10 +0200 Gołdasz, Janusz; Sapiński, Bogdan; Jastrzębski, Łukasz; Kubik, Michal
rodzaj: artykuł w czasopiśmie
Abstrakt: This study concerns the modeling of the hysteretic behavior of magnetorheological (MR) dampers. In general, hysteresis is one of key factors influencing the output of such actuators. So far, more attention has been paid to studying the combined hysteretic behavior of MR actuators by observing the relationships between the output (force/torque) and the inputs (current, velocity, and position). However, these devices feature two distinct hysteretic mechanisms: mechanical/hydraulic and magnetic. The mechanical hysteresis is of different nature than the magnetic hysteresis due to the properties of ferromagnetic materials forming the actuator's electromagnet circuit, and these should be split in the modeling process. In the present study, we separate the magnetic hysteresis from the mechanical/hydraulic one by investigating the magnetic flux vs. exciting current relationship of a commercial flow-mode MR damper subjected to sinusoidal current loading and independently of the mechanical excitations. The resulting behavior of the electromagnetic circuit is then examined using the non-linear inductor approach with hysteresis. Total hysteresis is then modeled using a non-linear inductor model in combination with a phenomenological parametric Maxwell type model of the damper.]]>
<![CDATA[Determination of a bubble drag coefficient during the formation of single gas bubble in upward coflowing liquid]]> Tue, 13 Oct 2020 11:42:50 +0200 Luty, Przemysław; Prończuk, Mateusz
rodzaj: artykuł w czasopiśmie
Abstrakt: Bubble flow is present in many processes that are the subject of chemical engineering research. Many correlations for determination of the equivalent bubble diameter can be found in the scientific literature. However, there are only few describing the formation of gas bubbles in flowing liquid. Such a phenomenon occurs for instance in airlift apparatuses. Liquid flowing around the gas bubble creates a hydraulic drag force that leads to reduction of the formed bubble diameter. Usually the value of the hydraulic drag coefficient, cD, for bubble formation in the flowing liquid is assumed to be equal to the drag coefficient for bubbles rising in the stagnant liquid, which is far from the reality. Therefore, in this study, to determine the value of the drag coefficient of bubbles forming in flowing liquid, the diameter of the bubbles formed at different liquid velocity was measured using the shadowgraphy method. Using the balance of forces affecting the bubble formed in the coflowing liquid, the hydraulic drag coefficient was determined. The obtained values of the drag coefficient differed significantly from those calculated using the correlation for gas bubble rising in stagnant liquid. The proposed correlation allowed the determination of the diameter of the gas bubble with satisfactory accuracy.]]>
<![CDATA[Complexity in economic and social systems: cryptocurrency market at around COVID-19]]> Tue, 13 Oct 2020 11:14:55 +0200 Drożdż, Stanisław; Kwapień, Jarosław; Oświęcimka, Paweł; Stanisz, Tomasz; Wątorek, Marcin
rodzaj: artykuł w czasopiśmie
Abstrakt: Social systems are characterized by an enormous network of connections and factors that can influence the structure and dynamics of these systems. Among them the whole economical sphere of human activity seems to be the most interrelated and complex. All financial markets, including the youngest one, the cryptocurrency market, belong to this sphere. The complexity of the cryptocurrency market can be studied from different perspectives. First, the dynamics of the cryptocurrency exchange rates to other cryptocurrencies and fiat currencies can be studied and quantified by means of multifractal formalism. Second, coupling and decoupling of the cryptocurrencies and the conventional assets can be investigated with the advanced cross-correlation analyses based on fractal analysis. Third, an internal structure of the cryptocurrency market can also be a subject of analysis that exploits, for example, a network representation of the market. In this work, we approach the subject from all three perspectives based on data from a recent time interval between January 2019 and June 2020. This period includes the peculiar time of the Covid-19 pandemic; therefore, we pay particular attention to this event and investigate how strong its impact on the structure and dynamics of the market was. Besides, the studied data covers a few other significant events like double bull and bear phases in 2019. We show that, throughout the considered interval, the exchange rate returns were multifractal with intermittent signatures of bifractality that can be associated with the most volatile periods of the market dynamics like a bull market onset in April 2019 and the Covid-19 outburst in March 2020. The topology of a minimal spanning tree representation of the market also used to alter during these events from a distributed type without any dominant node to a highly centralized type with a dominating hub of USDT. However, the MST topology during the pandemic differs in some details from other volatile periods.]]>
<![CDATA[Optimal selection of inner-branches parameters of matching circuits under the minimum branch-current RMS values and zero active-power conditions]]> Tue, 13 Oct 2020 11:10:43 +0200 Jaraczewski, M.
rodzaj: artykuł w czasopiśmie
Abstrakt: The article is a continuation of a study on the synthesis of matching multi-terminal networks, also known as compensators. The reactive four-terminal-network compensators for linear loads were introduced in previous publications, but it appeared that they operate effectively with nonlinear loads too. The methods to create a compensator for a mono-harmonic source, which allows complete independence of input from output waveforms, ensuring optimal operating conditions for the source, are presented herein. The work for the first time presents the optimal four-terminal-network compensator applied to a nonlinear load.]]>
<![CDATA[On simplified calculations of leakage inductances of power transformers]]> Tue, 13 Oct 2020 10:44:06 +0200 Sobczyk, Tadeusz; Jaraczewski, Marcin
rodzaj: artykuł w czasopiśmie
Abstrakt: This paper deals with the problem of the leakage inductance calculations in power transformers. Commonly, the leakage flux in the air zone is represented by short-circuit inductance, which determines the short-circuit voltage, which is a very important factor for power transformers. That inductance is a good representation of the typical power transformer windings, but it is insufficient for multi-winding ones. This paper presents simple formulae for self- and mutual leakage inductance calculations for an arbitrary pair of windings. It follows from a simple 1D approach to analyzing the stray field using a discrete differential operator, and it was verified by the finite element method (FEM) calculation results.]]>
<![CDATA[Tension-strut systems in conservation of historical buildings: examples of applications]]> Tue, 13 Oct 2020 10:38:41 +0200 Jurczakiewicz, S.; Karczmarczyk, S.
rodzaj: artykuł w czasopiśmie
Abstrakt: Tension-strut systems consist of thin cables and membranes capable of carrying only tensile forces and compressed struts cooperating with them. They make very effective use of strength properties of materials. They are lightweight and common in large span structures such as bridges and stadium roofs. However, they may also be advantageous in reinforcing and repairing historical buildings as they conform to conservation law in force. This paper presents a few examples of such applications of tension-strut system. Stabilization of historic brick and stone vaults with buttresses and iron bowstrings often turns out inadequate to resist thrust forces transmitted from the vault to the walls which cause cracks and deformations of the vault. Properly designed tension-strut structure can resist the thrust forces calculated in a theoretical way. Moreover, it can be hidden in the attic of building. Old timber roof structures are usually deformed and excessively deflected. Skilfully assembled tension-strut systems enable straightening and geometrical adjustment of a roof structure. Although similar threats and structural damages occur in most buildings which are a few hundred years old, individual design solutions are required in each case. Historical investigation and detailed measurement of geometry and deflections have to be made before choosing the apprioprate method of reinforcing the old structure.]]>
<![CDATA[Fire properties of intumescent coating systems for the rolling stock]]> Sat, 10 Oct 2020 08:33:05 +0200 Radek, Norbert; Dwornicka, Renata
rodzaj: artykuł w czasopiśmie
Abstrakt: This paper presents results of the experimental research aimed at fire and smoke properties of rolling stock coating system. The overriding research task was to meet current European requirements in the field of fire properties with maintaining the desired performance parameters, such as protective and decorative properties. The research determined parameters such as flame spreading over the surface and heat emission of coating system prepared on steel substrate. Research was carried out to find the optimum thickness of intumescent layer. The tests have shown the effectiveness of use of a protective paint that allows meeting the requirements in the field of fire safety.]]>
<![CDATA[Implementation of virtual reference points in registering scanning images of tall structures]]> Fri, 09 Oct 2020 14:30:55 +0200 Granek, Grzegorz; Toś, Cezary; Wolski, Bogdan
rodzaj: artykuł w czasopiśmie
Abstrakt: The concept of obtaining uniform and highprecision 3D models of large and complex engineering structures based on terrestrial laser scanning surveys highly depends on the accuracy of registering a series of adjacent scans. If it is not possible to place the required number of reference points in the observation scene, and there are no identifiable structural elements that could serve as such reference points, the issue can be solved by using the virtual reference points. The virtual reference points are not marked, but their position can be re-created in the post-processing of the scans on the basis of the geometrical features of the object. In the case of an industrial chimney, these can be the structural axis points determined at arbitrarily selected altitudes. In the solution presented herein, the coordinates of the reference points were independently determined twice: in the geodetic coordinate system using traditional method, in the local system of the scanner using the bisector of the chord of the circle, and by approximation of the circular arc shape of the chimney shell. Both procedures are preceded by the filtration of outliers. The concept of virtual reference points was verified by the measurement of the verticality of the axis and the structural geometry of a steel industrial chimney, which was accessible only on the foundation level.]]>
<![CDATA[Analysis of changes in the microstructure of geopolymer mortar after exposure to high temperatures]]> Fri, 09 Oct 2020 14:29:57 +0200 Dudek, Marta; Sitarz, Mateusz
rodzaj: artykuł w czasopiśmie
Abstrakt: The inorganic structure formed at the stage of setting of the geopolymer binder ensures high durability of the material under high-temperature conditions. However, changes in the microstructure of the material are observed. The purpose of the study was to analyze changes in the structure of geopolymer mortar after exposure to high temperatures T = 200, 400, 600, 800, and 1000 ◦C. Mortars with a binder based solely on fly ash (FA) and mixed in the 1:1 ratio with a binder containing fly ash and ground granulated blast-furnace slag (GGBFS) were tested. The descriptions of their microstructures were prepared based on digital microscope observations, scanning electron microscope (SEM) observations, EDS (energy dispersive spectroscopy) analysis, and mercury intrusion porosimetry (MIP) porosity test results. Changes in the material due to high temperature were observed. The differences in the microstructure of the samples are also visible in the materials that were not exposed to temperature, which was influenced by the composition of the materials. Porosity increases with increasing annealing temperature. The distribution of individual pores also changes. In both materials, the proportion of pores larger than 1000 nm increases with the temperature increase. Moreover, the number of cracks and their width also increases, reaching 20 µm in the case of GGBFS. Furthermore, the color of geopolymers has changed. The obtained results extend the current state of knowledge in the field of changes in the microstructure of geopolymers subjected to high temperature.]]>
<![CDATA[Ochrona i ekspozycja miejsc kulturowych niezachowanych rezydencji Radziwiłłów]]> Fri, 09 Oct 2020 12:06:57 +0200 Zin, Barbara
rodzaj: artykuł w czasopiśmie
Abstrakt: Prowadzone badania mają przyczynić się do upowszechnienia wiedzy i pobudzenia świadomości społecznej związanej z szeroko pojętą ochroną dziedzictwa kulturowego. Analiza stanu zachowania miejsc kulturowych, w których w przeszłości istniały obiekty rezydencjonalne świadczące o wysokich wartościach historycznych i architektonicznych, ma doprowadzić do wypracowania wspólnego rozumienia i interpretacji ochrony tych miejsc. Próba wytyczenia przez autorkę europejskiego szlaku siedzib radziwiłłowskich przyczyniła się do wyodrębnienia pięciu kategorii pod względem zachowania obiektów. Kategoria obiektów niezachowanych to największy zasób nieistniejących już siedzib rodowych Radziwiłłów. Znalazły się w niej znakomite dzieła architektury rezydencjonalnej, których relikty lub już tylko miejsca historyczne można ocalić od zapomnienia poprzez zbudowanie zbiorowej pamięci. Badania w artykule zostały przedstawione na przykładzie zamku w Goniądzu w Polsce i pałacu w Mańkiewiczach na Białorusi.]]>