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1
Content available Modeling of Eutectic Formation in Al-Si Alloy Using A Phase-Field Method
Ebrahimi Z.
Archives of Metallurgy and Materials
|
2017
|
Vol. 62, iss. 4
1969--1981
EN
We have utilized a phase-field model to investigate the evolution of eutectic silicon in Al-Si alloy. The interfacial fluctuations are included into a phase-field model of two-phase solidification, as stochastic noise terms and their dominant role in eutectic silicon formation is discussed. We have observed that silicon spherical particles nucleate on the foundation of primary aluminum phase and their nucleation continues on concentric rings, through the Al matrix. The nucleation of silicon particles is attributed to the inclusion of fluctuations into the phase-field equations. The simulation results have shown needle-like, fish-bone like and flakes of silicon phase by adjusting the noise coefficients to larger values. Moreover, the role of primary Al phase on nucleation of silicon particles in Al-Si alloy is elaborated. We have found that the addition of fluctuations plays the role of modifiers in our simulations and is essential for phase-field modeling of eutectic growth in Al-Si system. The simulated finger-like Al phases and spherical Si particles are very similar to those of experimental eutectic growth in modified Al-Si alloy.
2
Content available The determinants of the dynamics of business processes
Lewicki A., Czyżewska M.
Organizacja i Zarządzanie : kwartalnik naukowy
|
2016
|
nr 3
75--84
EN
The article presents the properties of the market system consisting of economic entities subjected to processes determined by the natural behavior of the nonlinear dissipative system. The rules of chaos govern this system, but they are associated with the system’s goal to reach an equilibrium. It is done using the mechanism of emergence, phase transition, and nomicity rules. This is often accomplished at the cost of unpredictable and undefined fluctuations that even in the case of a single object may affect the balance, or even cause a crisis of the entire system. However, we can prevent this by fulfilling certain conditions and by assuming the appropriate model of bottom-up management.
PL
W artykule przedstawiono własności systemu rynkowego, złożonego z podmiotów gospodarczych, podlegających procesom determinowanym przez naturalne zachowania dyssypatywnego układu nieliniowego. W układzie tym rządzą prawa chaosu, ale są one związane z dążeniem przez układ do osiągnięcia stanu równowagi. Odbywa się to z wykorzystaniem mechanizmu emergencji, przejść fazowych i praw nomiczności. Jest to realizowane bardzo często jednak również kosztem nieprzewidywalnych i nieokreślonych fluktuacji, które nawet w przypadku pojedynczego obiektu mogą wpływać na zachwianie równowagi, a nawet kryzys całego systemu. Możemy jednak temu zapobiegać, spełniając pewne uwarunkowania i przyjmując właściwy model zarządzania oddolnego.
3
Content available remote Statistical Fluctuations along the Lennard-Jones Melting Curve
Patra R., Heyes D. M.
Computational Methods in Science and Technology
|
2016
|
Vol. 22, No. 1
5--17
EN
Statistical fluctuations and correlations between thermodynamic properties along the fluid side of the melting line of the Lennard-Jones (LJ) are determined using Molecular Dynamics (MD) computer simulation. Linear regression, the Pearson coefficient and other statistical measures are calculated. The cross correlation between the configurational part of the pressure and potential energy, and the repulsive and attractive parts of the potential energy are focussed on. Regression plots show that at constant temperature and constant total energy the Weeks-Chandler-Andersen (WCA) decomposition of the Lennard-Jones repulsive and attractive potential energy components show a qualitative change along the melting line. At low temperature the two components are correlated, while they are anticorrelated in the high temperature limit. There is an intermediate temperature range in which the two potential energy components are effectively uncorrelated. The various fluctuation trends along the melting line were found to be weakly dependent on the force field used to generate the distribution of states, namely, the LJ potential, inverse power potential with exponent 12, and the repulsive term in the WCA decomposition of the LJ potential.
4
Parametry opisujące jakość energii elektrycznej
Hołdyński G., Skibko Z.
Elektro Info
|
2014
|
nr 12
22--24
PL
W artykule przedstawiono podstawowe parametry opisujące jakość energii elektrycznej, takie jak: częstotliwość, odchylenia, wahania, asymetria oraz harmoniczne napięcia. Podano również przyczyny i skutki występowania najczęściej spotykanych zakłóceń, oraz wymagania stawiane parametrom jakościowym energii.
EN
The article presents the basic parameters of the electric energy quality, so as: frequency, deviations, fluctuations, asymmetry and harmonic of voltage. The article additionally contains the causes and effects causes and effects of most often appearing disturbances, and requirements for parameters of the energy quality.
5
Content available Study of the state a Francis turbine
Żółtowski M., Żółtowski B., Castaneda L.
Polish Maritime Research
|
2013
|
nr 2
41--47
EN
This paper presents a methodology to evaluate the technical state of a Francis turbine by shaft rotor dynamic simulation. There are several rotor dynamic criteria that define the technical state of a turbo-machine. To feed the shaft rotor dynamic model this delivers the required information to accomplish the technical assessment. The numerical rotor dynamic model uses as input, the field forces obtained by the fluid-solid interaction analysis undertaken over the blades of the runner. The rotor dynamic numerical simulations allow to determinate the record-in-time of the displacements of any point along the shaft. This information is relevant for diagnosis tasks, because it is possible to decompose it spectrally and to estimate the severity of the vibrations. Comparing the results of the numerical model against those obtained from machines that operates under normal conditions, it is possible to determinate the technical state of the turbo-machine. This allows studying the stability of the turbine working on several operation ranges. A Francis turbine is a very complex machine that involves many physical phenomena of different nature. In this way, the hydraulic input forces needed by the rotor dynamic model should not be assumed but calculated directly from the fluid interaction over the turbine structure.
6
Burza słoneczna skali międzyplanetarnej - zagrożenia i szanse opanowania
Malko J.
Energetyka
|
2012
|
nr 5
210-213
PL
Ogromne fluktuacje pola magnetycznego w magnetosferze ziemskiej powodują wielkie przepływy prądu elektrycznego w górnych warstwach atmosfery i indukują przepływy w sieciach infrastrukturalnych, prowadzące do katastrofalnych awarii systemów elektroenergetycznych w skali planetarnej. W latach 2012-2013 Słońce wchodzi w fazę maksimum aktywności.
EN
Enormous fluctuations of magnetic field in the Earth’s magnetosphere are causing immense electric current flows in the upper atmosphere and inducing current surges in infrastructural networks resulting in massive planetary blackouts. In the 2012-2013 period the Sun enters solar maximum.
7
Content available remote A long-term trend and temporal fluctuations of the sea level at the Polish Baltic coast
Wiśniewski B., Wolski T., Musielak S.
Oceanological and Hydrobiological Studies
|
2011
|
Vol. 40, No.2
96-107
EN
The analysis of sea level record series along the Polish coast is presented. The main aim was to identify linear trends in the sea level changes at the coastal (Świnoujście, Kołobrzeg, Ustka, Łeba, Władysławowo, Hel, Gdynia, Gdańsk), lagoonal (Trzebież, Tokmicko) and riverine (Szczecin) gauge stations. The analysis showed individual coastal stations to differ in the rate of sea level changes. During 60 years of continuous observations (1947-2006), the differences varied from 1.0 (the western part of the coast) to 2.5 mm year-1 (the eastern part of the coast). The longest, more than 100-yr-long data series showed the sea level rise in Świnoujście and Kołobrzeg to be about 0.5 mm year-1; 1.57 mm year-1 being revealed in Gdańsk. Spectral analysis applied to the data showed numerous fluctuations and cyclicity in changes of the annual mean sea level at the Polish coast. A distinct, major 3-year cycle was revealed. In addition, three secondary cycles of 4.6, 6.7, and 8.6 years were present in the data, more or less clearly identifiable at individual stations.
8
Content available Numerical Method for Modeling of Acoustic Waves Propagation
Dykas S., Wróblewski W., Rulik S., Chmielniak T.
Archives of Acoustics
|
2010
|
Vol. 35, No. 1
35-48
EN
In this paper, numerical results of modeling of acoustic waves propagation are presented. For calculation of the acoustic fluctuations, a solution of the full non-linear Euler equation is used. The Euler equations are solved with the use of a numerical scheme of third-order accuracy in space and time. The paper shows a validation process of the described method. This method is suitable also for an aerodynamic noise assessment on the basis of unsteady mean flow field data obtained from a CFD calculations. In such case this method is called a hybrid CFD/CAA method. The proposed method is numerically decoupled with CFD solution, therefore the information about the mean unsteady flow field can be obtained using an arbitrary CFD method (solver). The accuracy of the acoustic field assessment depends on the quality of the CFD solutions. This decomposition reduces considerably the computational cost in comparison with direct noise calculations. The presented Euler acoustic postprocessor (EAP) has been used for modeling of the acoustic waves propagation in a cavity and in the flow field around a cylinder and an aerodynamic profile.
9
Content available Study Of The Technical State Of A Francis Turbine By Rotor Dynamic Simulations
Żółtowski B., Castaneda Heredia L., Barbosa J.
Journal of Polish CIMAC
|
2009
|
Vol. 4, no 3
113-123
EN
This paper presents a methodology to evaluate the technical state of a Francis turbine by shaft rotor dynamic simulation. There are several rotor dynamic criteria that define the technical state of a turbomachine. To feed the shaft rotor dynamic model this delivers the required information to accomplish the technical assessment. The numerical rotor dynamic model uses as input, the field forces obtained by the fluid-solid interaction analysis undertaken over the blades of the runner. The rotor dynamic numerical simulations allow to determinate the record-in-time of the displacements of any point along the shaft. This information is relevant for diagnosis tasks, because it is possible to decompose it spectrally and to estimate the severity of the vibrations. Comparing the results of the numerical model against those obtained from machines that operates under normal conditions, it is possible to determinate the technical state of the turbomachine. This allows studying the stability of the turbine working on several operation ranges. A Francis turbine is a very complex machine that involves many physical phenomena of different nature. In this way, the hydraulic input forces needed by the rotor dynamic model should not be assumed but calculated directly from the fluid interaction over the turbine structure.
10
Content available A survey of multiplicity fluctuations in PHENIX
Mitchell J.
Nukleonika
|
2006
|
Vol. 51,suppl.3
89-92
EN
The PHENIX Experiment at the Relativistic Heavy Ion Collider has made measurements of event-by-event fluctuations in the charged particle multiplicity as a function of collision energy, centrality, collision species, and transverse momentum in heavy-ion collisions. The results of these measurements will be reviewed and discussed.
11
Content available A statistical model analysis of yields and fluctuations in 200 GeV Au-Au collisions
Torrieri G., Jeon S., Rafelski J.
Nukleonika
|
2006
|
Vol. 51,suppl.3
99-103
EN
We show that the simultaneous measurement of yields and fluctuations is capable of falsifying and constraining the statistical hadronization model. We show how such a measurement can test for chemical non-equilibrium, and distinguish between a high temperature chemically equilibrated freeze-out from a supercooled freeze-out with an oversaturated phase space. We perform a fit, and show that both yields and fluctuations measured at RHIC 200 GeV can be accounted for within the second scenario, with both the light and strange quark phase space saturated significantly above detailed balance. We point to the simultaneous fit of the K/đ fluctuation and the K*/K ratio as evidence that the effect of hadronic re-interactions after freeze-out is small.
12
Content available remote Formation of soft material in terms of a coupled matter migration-and-relaxation picture: a synchronous mode
Gadomski A., Dressler M., Santamaría-Holek I., Rubi J. M.
Materials Science Poland
|
2006
|
Vol. 24, No. 4
935--949
EN
This study is devoted to draw a mesoscopic nonequilibrium thermodynamics (mnet)-based description of the model soft material, such as that made of clusters of amphiphilic molecules or biopolymer surfactants. The description offered also enters the region of nonlinear viscoelastic behaviour of soft-matter agglomerates, both in a fluctuation-driven (quantitatively, being realized in an synchronous mode) and some flow-driven (mostly, qualitatively) regime. A special emphasis is placed on a novel concept, termed the emergent (power-law) behaviour, which tries to effectively combine data available about specific soft-matter (complex) systems that under variety of physicochemical conditions often manifest a certain interesting mesoscopic properties
13
Content available Efekty szumowe w termometrii
Jacyszyn S., Stadnyk B, Łucyk J., Skoropad F.
Pomiary Automatyka Kontrola
|
2003
|
R. 49, nr 7-8
15-17
PL
W artykule przedstawiono analizę efektów szumowych w termometrii. Na przykładach wyników badań przetworników szumowych, rezystancyjnych oraz termoelektrycznych wyznaczono rolę fluktuacji stanu termodynamicznego w stabilności charakterystyk statycznych nominalnych i ich zmian w czasie eksploatacji czujników.
EN
The analysis of noise effects in thermometry is presented here. The progress in signal processing based on the computer technologies is complicated. Therefore estimation of measurement errors considers the estimation of thermodynamic forces and flows. The forces and the flows of electric genesis in electro transducers are the main problem. They are responsible for the nominal characteristics and their changes by means of electro thermal noises. The other kinds of noises are responsible for the deviations of the characteristics. These kinds are considered with help of the main equation of thermodynamics. The lack of processes in thermoelement material has been required the broad investigations with the help of different methods on the macro- and micro- levels, down to nanotechnology.
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