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Wyświetlanie 1-15 z 332
Tytuł:
1D and 2D finite-difference operators for periodic functions on arbitrary mesh
Autorzy:
Sobczyk, Tadeusz Jan
Powiązania:
https://bibliotekanauki.pl/articles/2042801.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
arbitrary meshes
finite-difference operators
partial finite difference operators
periodic function
two-variable periodic functions
Opis:
This paper presents novel discrete differential operators for periodic functions of one- and two-variables, which relate the values of the derivatives to the values of the function itself for a set of arbitrarily chosen points over the function’s area. It is very characteristic, that the values of the derivatives at each point depend on the function values at all points in that area. Such operators allow one to easily create finite-difference equations for boundaryvalue problems. The operators are addressed especially to nonlinear differential equations.
Źródło:
Archives of Electrical Engineering; 2022, 71, 1; 265-275
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Discrete-time feedback stabilization
Autorzy:
Mitkowski, W.
Bauer, W.
Zagórowska, M.
Powiązania:
https://bibliotekanauki.pl/articles/229169.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
stabilization
feedback stabilization
finite dimensional stabilization
infinite dimensional systems
finite dimensional approximations
continuous-discrete system
Opis:
This paper presents an algorithm for designing dynamic compensator for infinitedimensional systems with bounded input and bounded output operators using finite dimensional approximation. The proposed method was then implemented in order to find the control function for thin rod heating process. The optimal sampling time was found depending on discrete output measurements.
Źródło:
Archives of Control Sciences; 2017, 27, 2; 309-322
1230-2384
Pojawia się w:
Archives of Control Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of Thermal Stresses and Strains Developing During the Heat Treatment of Windmill Shaft
Autorzy:
Cebo-Rudnicka, A.
Malinowski, Z.
Telejko, T.
Powiązania:
https://bibliotekanauki.pl/articles/354018.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
stresses
fracture criterion
finite element method
Opis:
In the paper the results of evaluation of the temperature and stress fields during four cycles of the heat treatment process of the windmill shaft has been presented. The temperature field has been calculated from the solution to the heat conduction equation over the whole heat treatment cycles of the windmill shaft. To calculate the stress field an incremental method has been used. The relations between stresses and strains have been described by Prandtl-Reuss equation for the elastic-plastic body. In order to determine the changes in the temperature and stress fields during heat treatment of the windmill shaft self-developed software utilizing the Finite Element Method has been used. This software can also be used to calculate temperature changes and stress field in ingots and other axially symmetric products. In the mathematical model of heating and cooling of the shaft maximum values of the strains have been determined, which allowed to avoid the crack formation. The critical values of strains have been determined by using modified Rice and Tracy criterion.
Źródło:
Archives of Metallurgy and Materials; 2017, 62, 2A; 459-471
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some quantitative evaluations on finite difference local and global results
Autorzy:
Costamagna, E.
Powiązania:
https://bibliotekanauki.pl/articles/140996.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
finite differences
Schwarz-Christoffel
static fields
Opis:
Refined Schwarz-Christoffel (SC) conformal transformations allow us to perform reliable quantitative evaluation of the accuracy of local computation of electric and magnetic fields with limited effort, which can be useful to complement well known comparisons of global results. In this paper some examples are presented for mesh point potentials obtained by means of finite difference (FD) methods, but it is possible that similar considerations will be useful in the case of finite element methods (FEM) or meshless computations too.
Źródło:
Archives of Electrical Engineering; 2016, 65, 2; 263-272
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Coupled Smoothed Finite Element-Boundary Element Method for Structural-Acoustic Analysis of Shell
Autorzy:
Tian, W.
Yao, L.
Li, L.
Powiązania:
https://bibliotekanauki.pl/articles/177260.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
SFEM
smoothed finite element method
FEM
finite element method
BEM
boundary element method
structural-acoustic analysis
Opis:
Nowadays, the finite element method (FEM) – boundary element method (BEM) is used to predict the performance of structural-acoustic problem, i.e. the frequency response analysis, modal analysis. The accuracy of conventional FEM/BEM for structural-acoustic problems strongly depends on the size of the mesh, element quality, etc. As element size gets greater and distortion gets severer, the deviation of high frequency problem is also clear. In order to improve the accuracy of structural-acoustic problem, a smoothed finite-element/boundary-element coupling procedure (SFEM/BEM) is extended to analyze the structural-acoustic problem consisting of a shell structure interacting with the cavity in this paper, in which the SFEM and boundary element method (BEM) models are used to simulate the structure and the fluid, respectively. The governing equations of the structural-acoustic problems are established by coupling the SFEM for the structure and the BEM for the fluid. The solutions of SFEM are often found to be much more accurate than those of the FEM model. Based on its attractive features, it was decided in the present work to extend SFEM further for use in structural-acoustic analysis by coupling it with BEM, the present SFEM/BEM is implemented to predict the vehicle structure-acoustic frequency response analysis, and two numerical experiments results show that the present method can provide more accurate results compared with the standard FEM/BEM using the same mesh. It indicates that the present SFEM/BEM can be widely applied to solving many engineering noise, vibration and harshness (NVH) problems with more accurate solutions.
Źródło:
Archives of Acoustics; 2017, 42, 1; 49-59
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic anisotropy under arbitrary excitation in finite element models
Autorzy:
Bavendiek, Gregor
Leuning, Nora
Müller, Fabian
Schauerte, Benedikt
Thul, Andreas
Hameyer, Kay
Powiązania:
https://bibliotekanauki.pl/articles/140563.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
magnetic anisotropy
material modeling
finite element method
Opis:
Magnetic properties of silicon iron electrical steel are determined by using standardized measurement setups and distinct excitation parameters. Characteristic values for magnetic loss and magnetization are used to select the most appropriate material for its application. This approach is not sufficient, because of the complex material behavior inside electrical machines, which can result in possible discrepancies between estimated and actual machine behavior. The materials’ anisotropy can be one of the problems why simulation and measurement are not in good accordance.With the help of a rotational single sheet tester, the magnetic material can be tested under application relevant field distribution. Thereby, additional effects of hysteresis and anisotropy can be characterized for detailed modelling and simulation.
Źródło:
Archives of Electrical Engineering; 2019, 68, 2; 455-466
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of Mechanical, and Material Factors on the Biological Adaptation Processes of the Femoral Bone Implants
Autorzy:
Jasik, A.
Mroczek, M.
Powiązania:
https://bibliotekanauki.pl/articles/351931.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
orthopedic implants
stress
Finite Element Method (FEM)
Opis:
The study covers some aspects of the issue of determination of mutual connections between the mechanical and material factors, as well the biological implant adaptation processes. The main objective of the operation was adopted to develop models of cementless hip prosthesis company Fitmore Zimmer, taking into account the heterogeneity of material properties of bone tissue. These models were loaded in particular stages of the human gate and then they were used for the analysis of stress changes. The identification of the relations between the mechanical properties of osseous tissue required the conducting of computer simulations by means of the Finite Element Method (FEM).
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 1; 189-194
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Computing Reverberation Time in a 3D Room Model Using a Finite Difference Method Applied for the Diffusion Equation
Autorzy:
Kraszewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/177730.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
diffusion method
reverberation time
finite differences method
Opis:
The article presents theoretical values of reverberation times calculated on the basis of the diffusion equation for three room models: flat, cubic, and long. The article shows that not only the average absorp- tion coefficient, but also location of the absorbent material, as well as the place where the time is counted have an impact on the reverberation time, calculated on the basis of the diffusion equation. Despite that, the diffusion model is based on statistical assumptions. The primary goal of the article was to show that the model has geometrical features.
Źródło:
Archives of Acoustics; 2012, 37, 2; 171-180
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical Evaluation of the Vibration Reduction Index for Structural Joints
Autorzy:
Ramis, J.
Segovia, E.
Alba, J.
Carbajo, J.
Godinho, L.
Powiązania:
https://bibliotekanauki.pl/articles/177736.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
finite element model
vibration reduction
structural joints
Opis:
The present paper addresses the analysis of structural vibration transmission in the presence of struc- tural joints. The problem is tackled from a numerical point of view, analyzing some scenarios by using finite element models. The numerical results obtained making use of this process are then compared with those evaluated using the EN 12354 standard vibration reduction index concept. It is shown that, even for the simplest cases, the behavior of a structural joint is complex and evidences the frequency dependence. Comparison with results obtained by empirical formulas reveals that those of the standards cannot accurately reproduce the expected behavior, and thus indicate that alternative complementary calculation procedures are required. A simple methodology to estimate the difference between numerical and standard predictions is here proposed allowing the calculation of an adaptation term that makes both approaches converge. This term was found to be solution-dependent, and thus should be evaluated for each structure.
Źródło:
Archives of Acoustics; 2012, 37, 2; 189-197
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimal sliding control of mobile manipulators
Autorzy:
Galicki, M.
Powiązania:
https://bibliotekanauki.pl/articles/201159.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
mobile manipulator
trajectory tracking
finite time control
Opis:
The paper adresses optimal control problem of mobile manipulators. Dynamic equations of those mechanisms are assuemd herein to be uncertain. Moreover, unbounded disturbances act on the mobile manipulator whose end-effector tracks a desired (reference) trajectory given in a task (Certesian) space. A compytionally efficient class of two-stage cascaded (hierarchchical) control algotithms based on both the transpose Jacobian matrix and transpose actuation matrix, has been proposed. The offered control laws involve to kinds of non-singular terminal sliding mode (TSM) manifolds, which were also introduced in the paper. The proposed class of cooperating sub-controllers is shown to be finite time stable be fulfilment of practically reasonable assumptions. The performance of the proposed control strategies is illustated on an exemplary mobile manipulator whose end-effector tracks desired trajectory.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2019, 67, 4; 777-788
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Validation of finite element solutions of nonlinear, periodic eddy current problems
Autorzy:
Plasser, R.
Bíró, O.
Powiązania:
https://bibliotekanauki.pl/articles/140778.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
eddy currents
nonlinear magnetic
finite elements
3-dimensional
Opis:
An industrial application is presented to validate a finite element analysis of 3-dimensional, nonlinear eddy-current problems with periodic excitation. The harmonicbalance method and the fixed-point technique are applied to get the steady state solution using the finite element method. The losses occurring in steel reinforcements underneath a reactor due to induced eddy-currents are computed and compared to measurements.
Źródło:
Archives of Electrical Engineering; 2014, 63, 4; 591-600
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Design considerations of high-speed eddy-current brake
Autorzy:
Garbiec, T.
Kowol, M.
Kołodziej, J.
Powiązania:
https://bibliotekanauki.pl/articles/141585.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
eddy current brake
end-effect
finite element method
Opis:
The paper presents results of analysis of the influence of rotor construction on the steady-state torque-speed characteristics of a high-speed eddy-current brake. The investigation is carried out using two- and three-dimensional finite element models and measurements. A series of computations is carried out in order to find out the method for performance improvement of the considered system.
Źródło:
Archives of Electrical Engineering; 2014, 63, 2; 295-304
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Post-Quantum Cryptography: generalized ElGamal cipher over GF(2518)
Autorzy:
Hecht, P.
Powiązania:
https://bibliotekanauki.pl/articles/375655.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
post-quantum cryptography
non-commutative cryptography
finite fields
Opis:
Post-Quantum Cryptography (PQC) attempts to find cryptographic protocols resistant to attacks by means of for instance Shor's polynomial time algorithm for numerical field problems like integer factorization (IFP) or the discrete logarithm (DLP). Other aspects are the backdoors discovered in deterministic random generators or recent advances in solving some instances of DLP. The use of alternative algebraic structures like non-commutative or non-associative partial groupoids, magmas, monoids, semigroups, quasigroups or groups, are valid choices for these new kinds of protocols. In this paper, we focus in an asymmetric cipher based on a generalized ElGamal non-arbitrated protocol using a non-commutative general linear group. The developed protocol forces a hard subgroup membership search problem into a non-commutative structure. The protocol involves at first a generalized Diffie-Hellman key interchange and further on the private and public parameters are recursively updated each time a new cipher session is launched. Security is based on a hard variation of the Generalized Symmetric Decomposition Problem (GSDP). Working with GF(2518) a 64-bits security is achieved, and if GF(25116) is chosen, the security rises to 127-bits. An appealing feature is that there is no need for big number libraries as all arithmetic if performed in Z251 and therefore the new protocol is particularly useful for computational platforms with very limited capabilities like smartphones or smartcards.
Źródło:
Theoretical and Applied Informatics; 2016, 28, 4; 1-14
1896-5334
Pojawia się w:
Theoretical and Applied Informatics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlation of Hardness and Silicon Morphology for Al-Si-Sb Alloy
Autorzy:
Uzun, O.
Yilmaz, F.
Emeksiz, C.
Ergen, S.
Kolemen, U.
Powiązania:
https://bibliotekanauki.pl/articles/356738.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Al-Si alloy
casting
Vickers
finite element analysis
Opis:
In this study, we have focused on the role of silicon morphology on the hardness of eutectic Al–12 wt.% Si–0.5 wt.% Sb alloy solidified at different cooling rates. The alloys were produced by using induction melting, arc-remelting and melt-spinning techniques. The cooling rates of the alloys were determined as 0.5, 60 and ~105°C.s-1 for induction-melted, arc-remelted and meltspun alloy. The experimental results show that as the cooling rate increased the coarse silicon phase was substantially refined and its morphology altered from sharp need-like to round shape. Two exothermic peaks, attributed to precipitation and coarsening of silicon from supersaturated α-Al, were observed in the DSC curve of MS alloy. Vicker’s hardness of melt-spun alloy was found two times higher than those of IMed and ARed alloys. The lowest hardness of induction-melted alloy was ascribed to the lamellar morphology of silicon, yielding decohesive rupture. This result was confirmed by finite element analyzing.
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 1; 467-472
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Shot Peening on the Fatigue Strength of Automotive Tubular Stabilizer Bars DC 218
Autorzy:
Wittek, A. M.
Gąska, D.
Łazarz, B.
Matyja, T.
Powiązania:
https://bibliotekanauki.pl/articles/353092.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
shot-peening
residual stresses
fatigue
finite element method
Opis:
This paper concerns issues related to the development of designs of stabilizer bars for new motor vehicle models. It involves not only the designing of a stabilizer bar with the shape required by the manufacturer, but also the preparation of bending and heat treatment processes as well as the performance of strength and fatigue tests. In the prototype development phase, the simulations techniques (FEM) may be used to assess the design. The article contains a detailed analysis of a stabilizer bar designated with the DC 218 VA symbol. Performed numerical strength and fatigue calculations showed that the developed stabilizer bar design with the desired shape did not achieve the required number of fatigue cycles. It was also proven at the test stand by testing a prototype stabilizer bar. Therefore, it was suggested to supplement the technological process with an additional shot peening operation whose main aim was to reduce the length of microcracks on the stabilizer bar’s surface. This effect was confirmed during comparative metallographic tests of not shot – peened and shot – peened stabilizer bars. After shot peening, the analysed stabilizer bar reached a fatigue strength which exceeded the limits set by the manufacturer.
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 4; 1963-1968
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 332

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