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1
Content available The New Analytical Model of Free Resources in the Limited Availability Resources
Nowak Błażej, Stasiak Maciej, Zwierzykowski Piotr
Journal of Telecommunications and Information Technology
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2023
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nr 4
102--107
EN
The article presents a new analytical model for determining the probability of availability of a certain amount of well-defined free resources (e.g. a link) in a group of dedicated resources (e.g. a group of links) jointly serving a mixture of different classes of multiservice traffic. The presented method can be used to model access to resources in data centers, in particular in the software-defined networks, assuming – for reliability reasons – that the user should have access to a certain minimum number of specific separated resources. The proposed analytical model was verified by appropriate simulation experiments, which confirmed the satisfactory accuracy of the results obtained.
2
Content available remote Geophysical and analytical determination of overstressed zones in exploited coal seam: a case study
Chlebowski Dariusz, Burtan Zbigniew
Acta Geophysica
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2021
|
Vol. 69, no. 2
701--710
EN
A variety of geophysical methods and analytical modeling are applied to determine the rockburst hazard in Polish coal mines. In particularly unfavorable local conditions, seismic profling, active/passive seismic tomography, as well as analytical state of stress calculating methods are recommended. They are helpful in verifying the reliability of rockburst hazard forecasts. In the article, the combined analysis of the state of stress determined by active seismic tomography and analytical mod eling was conducted taking into account the relationship between the location of stress concentration zones and the level of rockburst hazard. A longwall panel in the coal seam 501 at a depth of ca.700 m in one of the hard coal mines operating in the Upper Silesian Coal Basin was a subject of the analysis. The seismic tomography was applied for the reconstruction of P-wave velocity felds. The analytical modeling was used to calculate the vertical stress states basing on classical solutions ofered by rock mechanics. The variability of the P-wave velocity feld and location of seismic anomaly in the coal seam in relation to the calculated vertical stress feld arising in the mined coal seam served to assess of rockburst hazard. The applied methods partially proved their adequacy in practical applications, providing valuable information on the design and performance of mining operations.
3
Content available remote Bending of beams with symmetrically varying mechanical properties under generalized load – shear effect
Magnucki Krzysztof, Lewinski Jerzy
Engineering Transactions
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2019
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Vol. 67, iss. 3
441--457
EN
The paper is devoted to simply supported beams with symmetrically varying mechanical properties in the depth direction. Generalized load of the beams includes the load types from uniformly distributed to point load (three-point bending). This load is analytically described with the use of a certain function including a dimensionless parameter. The value of the parameter is decisive for the load type. The individual nonlinear “polynomial” hypothesis is applied to deformation of a planar cross section. Based on the definitions of the bending moment and the shear transverse force the differential equation of equilibrium is obtained. The equation is analytically solved and the deflections are calculated for an exemplary beam family. The results of the study are specified in tables.
4
Content available Analytical calculations of surges caused by direct lightning strike to underground intrusion detection system
Aniserowicz K.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2019
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Vol. 67, nr 2
263--270
EN
The paper presents an analysis of overvoltages caused by a direct lightning strike in intrusion detection system equipped with underground radiating cable sensors. Waveforms of currents and voltages in the system components are calculated using analytical formulas basing on a transmission-line model in the frequency domain. The time-domain waveforms are computed using the inverse fast Fourier transform (IFFT). Three network configurations of the intrusion detection system are analyzed.
5
Content available remote The experimental and the theoretical analysis of the serviceability behavior of a deployable footbridge
Benjeddou O., Limam O., Ouezdou M. B.
Archives of Civil and Mechanical Engineering
|
2017
|
Vol. 17, no. 2
293--306
EN
This study presents a new concept of a deployable footbridge. The structural solution of the proposed footbridge comprises two parallel deployable beams as main girders and wooden boards which constitute the deck. The two beams were composed by several softwood blocks bonded to a unidirectional carbon fiber sheets layers by using an epoxy resin. In the first part of this study; we present the principle of the developed deployable footbridge. Thereafter, small-scale section prototype of the footbridge was tested under a vertical static nondestructive load on the Serviceability Limit State. The purpose of the tests is mainly to evaluate the vertical displacement responses under the static load, in every location of the prototype deck. The second purpose of these tests is to verify the deployment of the footbridge. Finally, a theoretical model based on the classical beam theory and on the theoretical structural behavior of the deployable beams was developed. The model presents the theoretical relationship between the load and the vertical displacement, under static loads, in every point of the footbridge. The predicted and the experimental results show a good agreement.
6
Content available remote Self-equilibrium geometry of the class-theta tetrahedral tensegrity module
Bieniek Z.
Engineering Transactions
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2016
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Vol. 64, iss. 4
441--448
EN
Tensegrity structures are mechanically stable because of the way in which they balance and distribute the mechanical stress, which is not principally a result of the strength of the individual components. This category of structures has the property that, even before the application of any external load, the members of the structure are already in tension or compression, that is, they are prestressed. There are different methods to find the equilibrium state attained by a tensegrity system for a given connectivity of the constituent cables and bars. In this paper, the tensegrity tetrahedron, characteristically shaped and free-standing, i.e., with no external loads, is investigated.
7
Content available remote Effect of temperature on crack kinking and jumping in a cross-ply laminated beam
Yamamoto S., Ikeda T., Senba A.
Archives of Mechanics
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2016
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Vol. 68, nr 5
349--369
EN
To understand the mechanisms of crack kinking and jumping that occur within the 90◦ layer of a cross-ply fiber reinforced plastic laminated plate, double cantilever beam tests were performed at several temperatures for laminated plates with two types of stacking sequences. The crack kink angles were calculated using a bi-layer shear-deformable beam model. Furthermore, the interlaminar shear stresses were calculated using finite-element models to clarify the mechanism of the repeated jumps. The following results were obtained from these experiment and analysis; (i) a crack at the center tended to propagate in a self-similar manner more stably at higher temperatures, (ii) the applied load at which value the crack at the center started propagation decreased as the 90◦ layer became thicker, and (iii) the crack along a 0◦/90◦ interface jumped to the other interface because the shear force along the 0◦/90◦ interface due to the thermal stress decreased as the crack propagated along the interface.
8
Symulator przenośnika taśmowego z uwzględnieniem uszkodzeń
Cenacewicz K., Przystałka P.
Modelowanie Inżynierskie
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2015
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T. 24, nr 55
13--20
PL
Przedstawiono aktualny stan prac w zakresie symulacyjnego modelu przenośnika taśmowego, w którym uwzględniono wpływ uszkodzeń. W ramach opracowania skupiono się na wybranych aspektach teoretycznych modelowania analitycznego oraz pokazano implementację symulatora obiektu badań z wykorzystaniem środowiska MATLAB®/Simulink®. Zalety i wady utworzonego symulatora zostały omówione przy uwzględnieniu wyników testów weryfikacyjnych, jakie uzyskano podczas badań.
EN
The paper presents the current state of the research dealing with the conveyor belt simulator, in which selected faults can be introduced. This study focuses on the most important aspects of analytic modelling of this kind of systems as well as on the implementation of the conveyor simulator with the use of MATLAB®/Simulink® software. The advantages and limitations of the simulator were investigated taking into account the verification results obtained at this stage of the research.
9
Content available Theoretical study of stress transfer in platelet reinforced composites
Fattahi A. M., Mondali M.
Journal of Theoretical and Applied Mechanics
|
2014
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Vol. 52 nr 1
3--14
EN
An analytical approach was developed for rectangular platelet reinforced composites which could be used for a 3D elastic stress field distribution subjected to an applied axial load. The ends of the platelet could be bonded to the matrix. Exact displacement solutions were derived for the matrix/platelet fromtheory of elasticity. These displacement solutions were then superposed for achieving analytical expressions for the matrix/platelet 3D stress field components over the entire composite system including the platelet end region, using the adding imaginary fiber technique. The platelet/matrix components could exactly satisfy the equilibrium and compatibility conditions and satisfy the equilibrium requirements and the overall boundary conditions. The obtained analytical results were then validated by FEM and Shear-lag modeling, and some of discrepancies among the shear-lag models were resolved. Good agreements were observed between the analytical and numerical predictions.
10
Wykorzystanie metod sztucznej inteligencji w projektowaniu procesów regulowanego azotowania gazowego stali
Mruk R., Michalski J., Słoma J., Wach P.
Inżynieria Powierzchni
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2014
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nr 3
3--10
PL
W artykule omówiono modele wspomagające projektowanie i symulacje procesów azotowania gazowego. Podano przykłady wykorzystania modeli: heurystycznych – umożliwiających wyznaczanie parametrów atmosfery wlotowej na pods tawie zakładanego przebiegu temperatury i potencjału azotowego w czasie trwania procesu; analitycznych – umożliwiających prognozowanie grubości warstwy azotowanej na podstawie kinetycznych współczynników wzrostu uzyskanych w badaniach grawimetrycznych; neu ronowych przeznaczonych do prognozowania właściwości warstwy azotowanej zdefiniowanej grubością efektywną i grubością warstwy azotków żelaza na podstawie wartości parametrów procesu azotowania. Wykazano, że zastosowane sieci neuronowe o właściwościach apr oksymujących pozwoliły na budowę modeli dobrze dopasowanych do danych eksperymentalnych, w których uwzględnione są zależności nieliniowe.
EN
The article discusses the various models used in the design and simulation of gas nitriding processes. Examples for the use o f models are presented, including: heuristic models, enabling the determination of the inlet atmospheric para meters on the basis of the estimated temperature changes and nitrogen levels during the nitriding process; analytical models, enabling the prediction of the thickness of the nitrided layer on the basis of growth kinetic coefficients derived from gravimetri c studies; neural models, enabling the forecasting of properties of the nitrided layer, defined by its effective thickness and the thickness of the iron nitride layer, on the basis of a nitriding process parameters. It has been demonstrated that the applie d neural networks with their approximating proper ties allow for the construction of models which are well suited to the experimental data which include non linear dependence.
11
Content available Mechanical-stress analytical modeling for the design of coils in power applications
Bellan D.
Archives of Electrical Engineering
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2014
|
Vol. 63, nr 4
579--590
EN
Modern electrical-power systems are often exploited for transmitting highfrequency carrier signals for communications purposes. Series-connected air-core coils represent the fundamental component allowing such applications by providing a proper filtering in the frequency domain. They must be designed, however, to withstand also the line short-circuit current. When a high-magnitude current flows through a coil, strong mechanical stresses are produced within the conductor, leading to possible damage of the coil. In this paper, an approximate analytical model is derived for the relationship between the maximum mechanical stress and the electrical/geometrical parameters of the coil. Such a model provides the guidelines for a fast and safe coil design, whereas numerical simulations are only needed for the design refinement. The presented approach can be extended to other applications such as, for example, the mechanical stress resulting from the inrush currents in the coils of power transformers.
12
Content available Wybrane problemy modelowania przewodzenia ciepła w badaniach nieniszczących materiałów kompozytowych
Świderski W., Vavilov V.
Problemy Techniki Uzbrojenia
|
2012
|
R. 41, z. 123
17--32
PL
W pracy przeprowadzono porównanie analitycznych i numerycznych metod stosowanych przy badaniu wymiany ciepła w materiałach kompozytowych, zawierających ukryte defekty typu naruszenia jednolitości (ciągłości). Poddano ocenie wykorzystywane oprogramowanie komputerowe oraz przedstawiono przewidywane kierunki rozwoju modeli badań termicznych.
EN
Analysis using analytical and numerical methods in investigation of exchange of heat in composite materials including hidden defects of disarrangement or uniformity (continuity) is carried out in the paper. The computer software used in this modeling is evaluated and future directions of development of thermal investigation models are presented too.
13
Content available remote Analytical modeling of passive electrodynamic levitation systems
Najjar-Khodabakhsh A.
Przegląd Elektrotechniczny
|
2010
|
R. 86, nr 10
354-358
EN
In this paper an analytical model for an electrodynamic levitation system is presented. The system consists of a moving permanent magnet piece levitated over a conducting plate. The width of conducting plate is assumed to be considerably greater than magnet. The permanent magnet piece is modeled by two equivalent current sheets, inducing eddy currents in the moving plate. The resultant magnetic field due to the permanent magnet and the eddy currents are then calculated. The drag and lift forces are also computed and their variations with system specifications are investigated. Finally a finite element method is employed to verify the validity of the analytical model, confirming the desirable accuracy of the model. The system modeling by the proposed analytical method is fast enough to be used in iterative design and optimization procedures.
PL
W pracy przedstawiono model systemu lewitacji elektrodynamicznej. System składa się z ruchomego magnesu lewitującego nad przewodzącą płytką o rozmiarach większych niż rozmiar magnesu. Magnes jest modelowany w postaci przewodzących prąd arkuszy indukujących prądy wirowe w płytce. Wypadkowe pole magnetyczne jest obliczane. Obliczane są też siły przyciągania i odpychania dla różnych warunków pracy. Przy zastosowaniu metody Elementów Skończonych przeprowadzono walidację modelu osiągając założoną dokładność.
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