Wyniki wyszukiwania - Biblioteka Nauki

1

Discrete element method [DEM] as a tool for investigating properties of granular materials

100%

Sykut J. , Molenda M. , Horabik J.

|

nr 2[A]

169-173

EN

With an increase in the scale of industrial operations the necessity of understanding the behaviour of granular materials and examining their properties becomes increasingly important. It is associated with rapid development of industries such as: food, chemical, pharmaceutical, cosmetic etc., in which materials in granular form are processed. One way of description of macroscopic behaviour of granular systems is a model including interactions between individual particles and between particle and elements of construction. Current needs of both technology and science call for the new research methods that provide more accurate results and enable closer examination of processes. Development of computational techniques resulted in the elaboration of Discrete Element Method (DEM). This article is focused on DEM as proposed by Cundall & Strack [1979] which enables interpretation of processes occurring in granular bedding considering phenomena on interparticle scale. The limitations and capabilities of DEM as well as results of modelling experimental investigations are addressed.

PL

Wzrost skali operacji przemysłowych wykonywanych na materiałach ziarnistych w wielu gałęziach przemysłu (spożywczego, chemicznego, farmaceutycznego, kosmetycznego i in.), niosie konieczność zrozumienia ich zachowania oraz badania ich właściwości mechanicznych. Jednym ze sposobów interpretacji efektów obserwowanych w ośrodkach granularnych jest stosowanie technik numerycznych do ich modelowania. Szerokie stosowanie materiałów w formie ziarnistej niesie potrzebę poszukiwania lepszych metod badawczych, których wykorzystanie zapewniałoby dokładność wyników oraz umożliwiało precyzyjną interpretację procesów zachodzących w złożu. Rozwój technik komputerowych w drugiej połowie XX wieku zaowocował powstaniem Metody Elementów Dyskretnych (DEM). Celem artykułu jest prezentacja, zaproponowanej przez Cundalla & Stracka [1979] metody numerycznej DEM, umożliwiającej analizę efektów obserwowanych w ośrodku sypkim poprzez uwzględnienie procesów zachodzących na poziomie mikrostrukturalnym. Zaprezentowano ograniczenia i możliwości metody oraz wyniki modelowania wybranych testów eksperymentalnych.

2

Real time computer tester for automatic voltage regulators used in marine generators

100%

Płachtyna O. , Bastian B. , Kutsyk A.

Poznan University of Technology Academic Journals. Electrical Engineering

|

2016

|

tom No. 85

465--476

EN

This article briefly introduces the characteristics of ships' electrical power networks, and an existing system is described as an example. A mathematical model of a selected power system, including generators with a drive and its loads, is presented. The algorithm implementing the author's numerical method, named 'the average step voltages method', is described. The chosen numerical method is notable for its stability and high accuracy, even in combination with a large integration step size. Software and hardware applications of the RT AVR tester are also shown. To check the adequacy of the simulations using the implemented model, experimental measurements were carried out. The measurements, including dynamic states, obtained by the computer tester with the AVR system, as well as the physical model with the AVR system, are summarized. Possibilities for usage in the marine industry in the future are also outlined.

3

Numerical evaluation of sound attenuation provided by periodic structures

100%

Martins M. , Godinho L. , Picado-Santos L.

Archives of Acoustics

|

2013

|

tom Vol. 38, No. 4

503--516

EN

The use of periodic structures as noise abatement devices has already been the object of considerable research seeking to understand its efficiency and see to what extent they can provide a functional solu- tion in mitigating noise from different sources. The specific case of sonic crystals consisting of different materials has received special attention in studying the influence of different variables on its acoustic performance. The present work seeks to contribute to a better understanding of the behavior of these structures by implementing an approach based on the numerical method of fundamental solutions (MFS) to model the acoustic behavior of two-dimensional sonic crystals. The MFS formulation proposed here is used to evaluate the performance of crystals composed of circular elements, studying the effect of varying dimen- sions and spacing of the crystal elements as well as their acoustic absorption in the sound attenuation provided by the global structure, in what concerns typical traffic noise sources, and establishing some broad indications for the use of those structures.

4

Investigation of E-Cigarette Smoking Model with Mittag-Leffler Kernel

100%

Uçar E. , Uçar S. , Evirgen F. , Özdemir N.

Foundations of Computing and Decision Sciences

|

2021

|

tom Vol. 46, No. 1

97--109

EN

Smoking is the most lethal social poisoning event. The World Health Organization defines smoking as the most important preventable cause of disease. Around 4.9 million people worldwide die from smoking every year. In order to analysis this matter, we aim to investigate an e-cigarette smoking model with Atangana-Baleanu fractional derivative. We obtain the existence conditions of the solution for this fractional model utilizing fixed-point theory. After giving existence conditions, the uniqueness of the solution is proved. Finally, to show the effect of the Atangana-Baleanu fractional derivative on the model, we give some numerical results supported by illustrative graphics.

5

Zastosowanie generatorów pseudolosowych w wyznaczaniu niepewności wyników numerycznych

100%

Jakubiec B. , Bąbka R.

Logistyka

|

2011

|

tom nr 6

PL

Wyznaczenie struktury i parametrów modelu matematycznego procesu zapisanego w postaci równań prowadzi do uzyskania wyników, których interpretacja pozwala na wysunięcie wniosków jakościowych i ilościowych w zakresie modelowanego zjawiska. W artykule przedstawiono zastosowanie generatorów pseudolosowych do oszacowania niepewności wyników numerycznych w celu oceny jakości modelu matematycznego pod względem dokładności otrzymanych wyników.

EN

Using mathematical equations as a model of the considered process, obtained result depends on its quality. The one of main problem includes the sensitivity of model parameters for accuracy of the numerical results. The paper deals with application of pseudorandom generators in testing dependencies between variation of model coefficients and uncertainty of obtained values estimated via computer simulation.

6

Heating of tissue by means of the electric field : numerical model basing on the BEM

100%

Majchrzak E. , Drozdek J. , Paruch M.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

|

2008

|

tom Vol. 7, nr 1

99-110

EN

The domain of tissue is subjected to the action of electrodes located on the skin surface. External electric field causes the heat generation in tissue domain. The distribution of electric potential in domain considered is described by the Laplace equation, while the temperature field is described by the Pennes equation. These problems are coupled by source function being the additional component in Pennes equation and resulting from the electric field action. The coupled problem is solved using the boundary element method. In the final part of the paper the examples of computations are shown.

7

Rozwiązywanie równań nieliniowych metodami numerycznymi

100%

Ufnalski W.

LAB Laboratoria, Aparatura, Badania

|

2005

|

tom R. 10, nr 1

42-48

8

Effective thermal conductivity of two-dimensional compacted granulates

100%

Szecówka M.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

|

2011

|

tom Vol. 10, nr 2

231-236

EN

This paper analyzes the heat transfer through systems formed by square grains with randomly assigned thermal conductivities subjected to different compactions. The efficiency of heat transport related to the density of the system is presented.

9

Numerical scheme for a two-term sequential fractional differential equation

100%

Błasik M.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

|

2011

|

tom Vol. 10, nr 2

17-29

EN

A numerical scheme is constructed to solve two-term sequential fractional differential equations with the orders of Caputo derivatives in the range (0,1). The proposed method is based on a corresponding existence-uniqueness theorem and transformation of the SFDE into an equivalent fractional integral equation. Numerical solutions are compared to analytical ones in two cases. An example with multiple solutions is also discussed.

10

A numerical approach in applying panel method for the added mass of a group of sections in fluids

88%

Zhang D. , Li P. , Wang Q. , Yang Y.

Archives of Mechanics

|

2023

|

tom Vol. 75, nr 1-2

151--168

EN

This paper firstly expands an efficient numerical methodology developed from the source panel method to the added mass calculation of long column systems in fluid. Structures submerged in fluid are considered as two-dimensional and are discretized into a number of source panels. The influence coefficient matrices and the potential function are then calculated and the fluid forces are calculated by the unsteady Bernoulli equation. Finally, we utilize this present method to calculate the mass coefficients of some typical problems, which effectively verifies its feasibility and accuracy. This method takes into account both applicability and computational efficiency. On the one hand, in contrast to the analytical method which is only applicable to specific cross-sections, this method is applicable to arbitrary boundaries with C0 continuity in mathematics. On the other hand, this method requires less mesh and computation than commercial software. This paper extends the application of the source panel method which is widely used in aerodynamics to provide a reference for added mass calculation problems in engineering.

11

Numerical propositions for integral equations in the light field with multiple reflections

88%

Hącia L.

Poznan University of Technology Academic Journals. Electrical Engineering

|

2009

|

tom No 59

73-85

EN

First the paper presents a multiple reflection method for calculation of luminous flux in interiors. The method of boundary integrals is applied. It leads to system of linear equations describing discrete values of overall luminous flux at particular surface elements of considered interior. Next, numerical propositions to solve integral equations modelling the light field with multiple reflections. Numerical examples are illustrated using the discretization method. In the paper quadrature method and projection methods (Galerkin method and collocation method) are proposed. In the future, a comparison between presented methods will be made.

12

Design and performance study of a small-scale waste heat recovery turbine

88%

Rusanov R. , Jędrzejewski Ł. , Klonowicz P. , Żywica G. , Lampart P. , Rusanov A.

Transactions of the Institute of Fluid-Flow Machinery

|

2016

|

tom nr 133

145--162

EN

The paper presents the design process of a radial-axial turbine working with SES36 working ﬂuid. First, the mean-line design process is performed and then the geometry is developed. In the next stage the numerical veriﬁcation is performed taking into account the real properties of the working ﬂuid. The properties are implemented via a look-up table and by a modiﬁed Benedict-Webb-Rubin equation of state. The presented turbine is characterized by a very small stator outﬂow angle which is about 4.5◦ but despite this small value, the eﬃciency of the machine is relatively high and equal to about 88%. The inﬂuence of internal leakages has also been investigated.

13

Methodology for underground mining method selection

88%

Mijalkovski S. , Peltechki D. , Despodov Z. , Mirakovski D. , Adjiski V. , Doneva N.

Mining Science

|

2021

|

tom Vol. 28

201--216

EN

The mining method selection for underground mining is one of the most important decisions when designing a mine. This selection depends on the mining-geological, mining-technical and economic factors. The mining method selection for underground mining can be described as a multi-criteria decision-making process, as several factors are involved in the selection process. In this paper, a methodology for rational and optimal mining method selection for underground mining of metallic mineral resources has been developed. First, a rational selection of the four best-ranked mining methods for underground mining is performed using numerical methods (Nicholas' approach and the modified approach of Nicholas, i.e., UBC selection of mining method). This is followed by the optimal selection of underground mining method using multi-criteria decision-making methods (ELECTRE, PROMETHEE, AHP, and integrated AHP-PROMETHEE) and by comparing the obtained rankings, the optimal mining method is selected.

14

Komputerowa analiza naprężeń i odkształceń w spągnicy przy obciążeniach asymetrycznych

88%

Polak-Micewicz M.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

|

2010

|

tom z. 96

69-70

EN

The paper presents possibilities of the engineering program ANSYS applied while construction of prototype of the roof supports in the firm FAZOS. Analysis of the obtained stresses allowed to prove correctness of the assumed boundary conditions, proved also by physical tests.

15

The three-band matrices

88%

Biernat G. , Boryś J. , Całusińska I. , Surma A.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

|

2008

|

tom Vol. 7, nr 2

119-122

16

Implementation and speed up of a parallel algorithm for the cauchy problem

75%

Purcz P.

Budownictwo o Zoptymalizowanym Potencjale Energetycznym

|

2009

|

tom nr (6)

258--263

EN

The speed up of a parallel algorithm with respect to sequential one for the case of the Cauchy problem. Four various known numerical methods are applied for solving of the problem. For each method a speed up function is determined. Then a really speed up is given for various number of used processors and points processed by a single processor. The algorithm was implemented on the platform MS .NET in MS Visual C# using a distributed calculation. The obtained results of the really speed up are comparable with theoretical speed up function. The numerical results indicate that efficiency of the parallel computations increases with the number of arithmetical operations needed for one step of used numerical methods.

17

Computer methods in stability analysis of elastic-plastic shell structures

75%

Zielnica J.

Zeszyty Naukowe Politechniki Poznańskiej. Maszyny Robocze i Transport

|

2002

|

tom Nr 54

215-228

EN

The paper deals with a general approach in stability analysis of elastic-plastic shell structures. Among all cylindrical shells under axisymmetrical loads were disscussed and analysed preferably in scientific publications because their application in engineering practice is very important. Also, spherical and conical shells of different shape were considered giving both analytical and numerical solutions. Computer methods are preferred in the solutions, because in most cases the resulting equations of stability problems are transcendental, so, the paper presents the main frames of the numerical iterative algorithms and their computer implementation. The algorithms make possible to perform a specific analysis of the considered problems, with taking into consideration possible imperfections, geometrical and material nonlinearities, boundary conditions and different loadings.

18

Zastosowanie metod numerycznych do modelowania procesu filtracji grawitacyjnej

75%

Piekarski J.

|

tom Tom 13

315-331

PL

W artykule przedstawiono autorski program komputerowy "FILTRA", zrealizowany w środowisku DELPHI 2006, do modelowania procesu przepływu medium przez warstwę porowatą oraz procesu filtracji grawitacyjnej. Aplikacja składa się z szeregu modułów, będących oddzielnymi podprogramami. Pierwszy moduł odnosi się do analizy granulometrycznej i realizuje na podstawie danych wstępnych, obliczenia i wykres krzywej składu ziarnowego oraz średnic charakterystycznych, które w kolejnym kroku działania aplikacji, eksportowane są do kolejnego modułu, związanego z obliczeniami współczynnika filtracji oraz przepuszczalności. Natomiast wielkości obliczone w tym module, stanowią dane wstępne, w kolejnym module związanym z obliczeniami przepływu medium przez warstwę porowatą oraz procesem filtracji grawitacyjnej.

EN

The article presents the author's computer program "FILTRA" implemented in Delphi 2006 environment. To ensure the possibility of subsequent modification, the application consists of several modules, which are separate subprograms. The first module refers to the grain size analysis and implements on the basis of preliminary data, calculations and plot of the grain size curve and characteristic diameters, which in the next step of application, are exported to the next module associated with calculation of filtration and permeability coefficients. Next, values calculated in this module are preliminary data for next module associated with the calculations of flow through porous layer and the process of gravitational filtration. The computer program "FILTRA" is a modern tool for simulation and calculations of flow processes through porous layer and the gravitational filtration of suspension taking into account creation of socalled colmatation blockades. The application allows to calculate and present characteristics of porous filter layer by granulometric analysis, which result in presentation of coefficient of heterogeneity of grain size and characteristic diameters: dMo, dMe, d10, d20, d50, d60 and graphs. The program calculates the value of filtration coefficient K [m/s] using method of variable pressure and for control, using the calculated characteristic values, it calculates value of filtration coefficient K [m/s] on the basis of empirical equations according to Hazen, Krüger, Seelheim, Slichter and USBSC. This application, on the basis of filtration coefficient K [m/s], determined using method of variable pressure, and value of coefficient of dynamic viscosity miZ of suspension [Nźs/m2] and suspension density gz [kg/m3] calculates and presents value of permeability coefficient k [m2] and for control, on the basis of porosity of bed E0 [-] substitute diameter dz [mm] it calculates the value of permeability coefficient kC [m2] using empirical equation according to Kozena-Carman. The program allows to visualize changes in the value of filtration coefficient K [m/s], permeability coefficient k [m2], colmatated bed porosity ES [-] and colmatation coefficient n [-] depending on time of medium surface lowering tS [s]. The program performs the calculations and visualization of characteristic parameters, presented in the paper, concerning flow through porous layer and the suspension gravitational filtration taking into account the phenomenon colmatation blockades.

19

The heat transferring in the pulse irradiated crystals with non-linear heat parameters

75%

Monastyrskii L. , Broda A.

Prace Naukowe. Chemia / Wyższa Szkoła Pedagogiczna w Częstochowie

|

2001

|

tom Vol. 5

161--169

EN

The processes of heat transfer in the pulse irradiated crystal with non-linear heat parameters was studied. The implicit numerical method applied. It has been showen, that the non-linearity of heat parameters essentially changes conditions of heating and cooling to a crystal. Time evolution of heat field in depth of crystals in different condition of pulse irradiation was investigated.

20

Chislovoj metod opredelenija naprjazhenno-deformirovannogo sostojanija i kriticheskikh nagruzok poteri ustojjchivosti arok

75%

Shebanin V. , Bogza V. , Bogdanov S. , Hilko I.

Motrol. Motoryzacja i Energetyka Rolnictwa

|

2013

|

tom 15

|

nr 2