Wyniki wyszukiwania - Biblioteka Nauki

1

Monitoring of dry sliding wear using fractal analysis

100%

Zhang J. , Regtien P. , Korsten M.

Metrology and Measurement Systems

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2005

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tom Vol. 12, nr 2

111-120

EN

Reliable online monitoring of wear remains a challenge to tribology research as well as to the industry. This paper presents a new method for monitoring of dry sliding wear using digital imaging and fractal analysis. Fractal values, namely fractal dimension and intercept, computed from the power spectrum of the images of a wearing surface, are adopted as indicators of the dynamic wear process. Experimental results show that progressive changes of fractal values might reveal the wear status of the surface.

PL

Niezawodne monitorowanic zużycia powierzchni w czasie rzeczywistym jest wyzwaniem dla badań z zakresu trybologii, a także dla praktyki przemysłowej. W artykule przedstawiono nową metodę monitorowania suchoślizgowego zużycia powierzchni z zastosowaniem zobrazowania cyfrowego i analizy fraktalnej. Parametry fraktalne, a mianowicie wymiar fraktaIny oraz intercept, obliczane z widma mocy obrazów zużytej powierzchni, są wykorzystywane jako wskaźnik dynamicznego procesu zużycia. Wyniki eksperymentalne pokazują, że progresywne zmiany parametrów fraktalnych mogą być miarą stopnia zużycia powierzchni.

2

Fractal analysis in two phase flow

100%

Mosdorf R. , Poniewski M. , Ulbrich R.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika

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1999

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tom Z. 67

303--312

EN

The paper presents principles of fractal analysis of measurement signals. The application of such indicators as autocorrelation function. Hurst exponent, the largest Lapunow exponent, correlation dimension. Kołmogorow entropy for the measuring signal analysis are discussed. The fractal analysis of experimental data was used to analyse the results of registration of local changes of gas void fraction in the flow of water-air mixture crosswise to the tube bundle in the shell-side space. The occurrence of low dimensional attractors of correlation dimensions close to D2=1.1 and D2=3.9 was found.

3

Temporal variations of correlation dimensions of local mining seismicity with relation to the rockburst generating process

100%

Mortimer Z. , Luca L. D.

Acta Geophysica Polonica

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1999

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tom Vol. 47, nr 3

273-282

EN

The studies concern variations in the spatial and temporal distribution of clusters of local mining induced seismic activity. As the descriptor of such clusters, the fractal correlation exponent dimension has been chosen. The results of testing on Monte Carlo simulated fractal sets show that a small size of temporal window allows us to get reliable estimates of correlation dimension and to study its variation as a short-time period precursor to rockbursts. The correlation between changes in time of spatial epicentre distribution D2 and temporal distribution Dt of epicentre and the occurrence of strong events was found, but not for the all data analysed. We cannot confirm the existence of some systematic evidence, but we found that an anomalous state of the fractal dimension could be observed prior to large events; however, there are no well determined features in its trend. Analysing the distribution of the intertime between the consecutive events, the dimension of its strange attractor has been calculated.

4

Application of Fractal Analysis Methods for Lift Height Optimization in Magnetic Force Microscopy Measurements

100%

Bramowicz M. , Kulesza S. , Chrostek T. , Senderowski C.

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tom 63

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nr 3

5

Fractal analysis of serial fundus images for retinal disease monitoring

100%

Berndt-Schreiber M. , Bieganowski L.

Machine Graphics and Vision

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2000

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tom Vol. 9, No. 1/2

433-438

EN

An attempt to apply fractal analysis in the interpretation of fundus images of retinal vessel patterns in the human eyes has been presented. An implementation of the algoriyhm estmating the fractal dimension of surfaces (accoding to the Minkowski-Bouligand definition) has been suggested within the framework of professional image processing software as an effective tool in a search for a classifying feature, supporting the retinal disease diagnosing. Preliminary test results demonstrating the possibilities of the proposed tool and further developments of the approach are discussed.

6

Application of Fractal Analysis Methods for Lift Height Optimization in Magnetic Force Microscopy Measurements

100%

Bramowicz M. , Kulesza S. , Chrostek T. , Sendrowski C.

Archives of Metallurgy and Materials

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2018

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tom Vol. 63, iss. 3

1109--1113

EN

The paper presents results of a research on simulation of magnetic tip-surface interaction as a function of the lift height in the magnetic force microscopy. As expected, magnetic signal monotonically decays with increasing lift height, but the question aris es, whether or not optimal lift height eventually exists. To estimate such a lift height simple procedure is proposed in the paper based on the minimization of the fractal dimension of the averaged profile of the MFM signal. In this case, the fractal dimension ser ves as a measure of distortion of a pure tip-surface magnetic coupling by various side effects, e.g. thermal noise and contribution of topographic features. Obtained simulation results apparently agree with experimental data.

7

Surface micromorphology characterization of PDI8-CN2 thin films on H-Si by AFM analysis

100%

Ţălu Ş. , Kulesza S. , Bramowicz M. , Solaymani S. , Ţălu M. , Nezafat N. B. , Rezaee S.

Materials Science Poland

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2020

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tom Vol. 38, No. 2

334--340

EN

A nanoscale investigation of three-dimensional (3-D) surface micromorphology of archetypical N, N0- bis (n-etyl) x:y, dicyanoperylene- 3, 4:9, 10 bis (dicarboximide) (PDI8-CN2) thin films on H-Si substrates, which are applicable in n-type semiconducting compounds, has been performed by using fractal analysis. In addition, surface texture characteristics of the PDI8-CN2 thin films have been characterized by using atomic force microscopy (AFM) operated in tapping-mode in the air. These analyses revealed that all samples can be described well as fractal structures at nanometer scale and their three dimensional surface texture could be implemented in both graphical models and computer simulations.

8

Changes in magnetic domain structure of maraging steel studied by magnetic force microscopy

100%

Bramowicz M. , Kulesza S. , Mrozek G.

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2014

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tom nr 17(4)

371--379

EN

The paper presents results on whether and how the magnetic domain structure in maraging steel undergoes any change due to the aging process. It continues the works on application of correlation methods and fractal analysis into studies of magnetic properties of various steel alloys using Scanning Probe Microscopy. It is aimed at verifying the usefulness of the structure function for description of spatial changes in shape and orientation of magnetic domains, and the magnitude of magnetic stray field affected by the heat treatment. Obtained results suggest that despite vanishing magnetic tip-surface interaction, and hence vanishing magnetic stray field, magnetic domains remain nearly perfectly isotropic although randomly oriented. Similar to isotropic real surfaces, the fractal dimension of the magnetic domains turns out to be independent of the structural changes induced by the aging process, whereas the topothesy is found to vary within order of magnitude along with changes in the magnetic stray field. After all, obtained results lead to conclusion that the aging process leaves its fingerprints in the structure of the steel alloys, which can be studied using numerical analysis of images of magnetic interactions between vibrating tip and the stray field.

9

Fractal characteristics of the ULF emissions along a meridian profile, based on the 210 MM stations data

100%

Varlamov A. , Smirnova N. , Hayakawa M. , Yumoto K.

Acta Geophysica

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2012

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tom Vol. 60, no. 3

928-941

EN

Fractal analysis of magnetic records (1 Hz sampling rate) of 5 stations (Guam, Moshiri, Paratunka, Magadan, and Chokurdakh) located along the 210 magnetic meridian (210 MM) has been performed using the Higuchi method. The period of 22 months (October 1992 to July 1994) that embodies the date of the strong Guam earthquake of 8 August 1993 has been considered. A comparison of the ULF emissions scaling parameters (spectral exponents β and fractal dimensions D) obtained at different latitudes has been made. Dependence of β and D on the Kp index of geomagnetic activity has been analyzed for each of the 24 local time intervals. It is revealed that D decreases (β increases) with increasing geomagnetic activity at all stations, but the rates of decrease (increase) are different at different stations and in different time intervals. It is shown that the evening, night and early morning hours are preferable to study magnetospheric effects, whereas the noon hours are the most suitable for the analysis of lithospheric effects. A possibility of using the data of the 210 MM stations as reference materials for the Guam seismically active area is discussed.

10

Characteristics of porous beds based on fractal parameters

100%

Bramowicz M. , Kulesza S. , Sobieski W.

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2017

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tom nr 20(2)

171--179

EN

The paper presents the results of a fractal analysis of the cross-sections of a porous mineral deposit consisting of spherical elements which formed a spatial system with varying porosity (0.4 to 0.95). The virtual deposit was generated using the Discrete Element Method in the YADE code by means of the so-called Radius Expansion Method. The fractal analysis was carried out using the structure function method, determining the fractal dimension (D), the topothesy (L) and the corner frequency (l) (MAINSAH et al. 2001). The conducted simulations have confirmed to a considerable extent the test results available in the literature involving the fractal analysis of mineral deposits with varying porosity. They clearly indicate that the fractal dimension does not change along with the porosity of the deposit, if the autocorrelation function or their transformations (e.g. structure function) methods are used. Moreover, based on the information available in the literature, it can be concluded that the value of the fractal dimension corresponds to mineral deposits with the specified geometric shapes of the elements which form them.

11

Fractal dimensions analysis of branching streamers propagating in mineral oil

100%

Dang V.-H. , Beroual A. , Rózga P.

Archives of Electrical Engineering

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2022

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tom Vol. 71, nr 3

659--669

EN

This article deals with the analysis of the fractal dimension of streamers propagating in mineral oil, under lightning impulse voltage, using the box counting method; the method and technique of calculation are described therein. In the considered experimental conditions, the average velocities of recorded streamers are of 2.4 km/s and 1.8 km/s for positive and negative streamers, respectively; these velocities correspond to the 2nd mode of streamers propagation. It is shown that the streamers present the fractal dimension D ; and the higher D is the bushier are the streamers (i.e. with high branch density). The positive streamers can have higher D than the negative ones, if they are bushier.

12

Application of fractal analysis to the characterization of microstructure of different food products

100%

Smoczynski M. , Dziuba Z. , Smietana Z. , Borowska J. , Pierzynowska-Korniak G.

Natural Sciences

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1999

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tom 03

13

The fractal characteristics of lattice media. Part II.

100%

Marciniak A. , Fijolek A. , Kwiecien S. , Podgorski J.

International Agrophysics

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1996

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tom 10

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nr 4

14

Structural and morphological properties of HA-ZnO powders prepared for biomaterials

88%

Moldovan M. , Prodan D. , Popescu V. , Prejmerean C. , Saroși C. , Saplonţai M. , Țălu S. , Vasile E.

Open Chemistry

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2015

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tom 13

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nr 1

EN

The purpose of this study was to investigate the structural and morphological properties of hydroxyapatite – zinc oxide (HA-ZnO) powders prepared to be used in an endodontic sealer formulation. The HA-ZnO was synthesized from hydroxyapatite (HA) in the presence of zinc oxide (ZnO) sol. The starting reagents were CaO, H3PO4 and a suspention of ZnO (25% in water). Following precipitation, the obtained sol was subjected to heat treatment at 110°C, 400°C, 850°C and 1050°C. The study focused on the influence of the thermal treatment on the cristallinity of precipitated powders. X-ray diffraction was used in order to study the structural properties of the obtained powder. Fourier Transform Infrared Spectroscopy (FT-IR) was used in order to evaluate the interactions between HA and ZnO. The morphology of the samples was studied by Scanning Electron Microscopy (SEM). Transmission Electron Microscopy and High Resolution Transmission Electron Microscopy (TEM, HRTEM) were used for the determination of particle size and fractal analysis. The fractal analysis of images using the standard box-counting method is presented and the results are discussed. It was demonstrated that the fractal dimension analysis is a useful method to quantitatively describe the complex microstructures and it can reveal the relation between fractal parameters.

15

Functional and Fractal Properties of Fe-Al Coatings After Gas Detonation Spraying (GDS)

88%

Chrostek T. , Rychlik K. , Bramowicz M. , Senderowski C.

Archives of Metallurgy and Materials

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2018

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tom Vol. 63, iss. 4

1993--1999

EN

The paper presents the results and provides an analyse of the geometric structure of Fe-Al protective coatings, gas-treated under specified GDS conditions. The analysis of the surface topography was conducted on the basis of the results obtained from the SEM data. Topographic images were converted to three-dimensional maps, scaling the registered amplitude coordinates of specific gray levels to the relative range of 0÷1. This allowed us to assess the degree of surface development by determining the fractal dimension. At the same time, the generated three-dimensional spectra of the autocorrelation function enabled the researchers to determine the autocorrelation length (Sal) and the degree of anisotropy (Str) of the surfaces, in accordance with ISO 25178. Furthermore, the reconstructed three-dimensional images of the topography allowed us to evaluate the functional properties of the studied surfaces based on the Abbott-Firestone curve (A-F), also known as the bearing area curve. The ordinate describing the height of the profile was replaced by the percentage of surface amplitude in this method, so in effect the shares of the height of the three-dimensional topographic map profiles of various load-bearing properties were determined. In this way, both the relative height of peaks, core and recesses as well as their percentages were subsequently established.

16

Characteristics of seismic activity in the Western, Central and Eastern parts of the North Anatolian Fault Zone, Turkey: Temporal and spatial analysis

88%

Öztürk S.

Acta Geophysica

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2011

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tom Vol. 59, no. 2

209-238

EN

Characteristics of seismic activity along the North Anatolian Fault Zone are analyzed between 1970 and 2010. Magnitude completeness changes between 2.7 and 2.9 in the North Anatolian Fault Zone. The frequency-magnitude distribution of earthquakes is well represented with a b-value typically close to 1. A clear decrease in temporal distribution of b-value is observed before the strong main shocks. Correlation dimension values are relatively large and the seismic activity is more clustered at larger scales in the North Anatolian Fault Zone. A statistical assessment is made in order to detect the current seismic quiescence anomalies in the beginning of 2010. Eight significant anomalous zones throughout the North Anatolian Fault Zone are detected. These are centered at: (1) 41.08°N-28.58°E (around Silivri), (2) 41.47°-29.51°E (in the Black Sea), (3) 40.69°N-29.78°E (including Izmit), (4) 40.26°N-26.46°E (around Gelibolu, Canakkale), (5) 40.59°N- 31.03°E (including Duzce fault), (6) 40.86°N-35.30°E (around Amasya), (7) 39.48°N-39.74°E (around Erzincan), and (8) 39.06°N-40.50°E (around Bingol).

17

Fractal analysis of carbonized porous material on the basis of mercuric porosymetry

88%

Mianowski A. , Owczarek M.

Polish Journal of Applied Chemistry

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2000

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tom Vol. 44, nr 2-3

95-103

EN

A method for the interpretation of the porosimetric data by means of fractal dimension has been proposed. Such an approach yields the parameters which can be used for the description of porous solids. The individual values of the parameter have been estimated for the selected substances of the extended mesopore systems. The model developed bases on the specific analysis of the macro- and mesopores.

18

Spatial variability of soil moisture in grassland

88%

Janik G.

International Agrophysics

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2005

|

tom 19

|

nr 1

19

Fractal analysis of adults cerebellum surface NMR observations

88%

Rybaczuk M. , Kedzia A.

Folia Morphologica

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1996

|

tom 55

|

nr 4

20

User activity detection in computer systems by means of recurrence plot analysis

75%

Rybak T. , Mosdorf R.

Zeszyty Naukowe Politechniki Białostockiej. Informatyka

|

2010

|

tom Z. 5

67-85

EN

As computers are getting faster and disks are growing bigger more data describing user behaviour can be gathered. These data can be analysed to gain insight into user behaviour and then to detect user traits. Currently many different methods are used to analyse data — and there is still no one best method for analysing different parameters of computer systems. Computer systems behave non-linearly because they run many programs on multi-user operating systems; this causes inter-program dependencies requiring nonlinear methods to analyse gathered data. The aim of the article is to present how non-linear methods are able to detect subtle changes introduced into system by user’s actions. Number of interrupts per second was chosen as variable describing system’s behaviour. Analysis presented in this article focuses on idle system and system busy accessing hardware. Article shows that using recurrence plot can reveal similarities in behaviour of the system running different programs, and therefore can be used to detect similarities and differences in users behaviour. This article presents analysis of system activity through usage of series of recurrence plots to detect changes introduced by user actions. Analysis of lengths of horizontal and vertical lines on recurrence plots allows for describing periodicity of the system. This allows for gaining insight into behaviour of entire computing environment. Article shows that different tasks (such as network transmission, writing or reading from CD-ROM, compressing data) result in different recurrence plots; at the same time changes introduced by those tasks are hard to detect without analysis data. This means that usage of recurrence plot is crucial in detecting changes introduced in system by user’s actions.

PL

Dzięki nieustannemu wzrostowi wydajności systemów komputerowych możemy gromadzić coraz więcej danych opisujących aktywność systemów. Dane te mogą być analizowane aby zyskać wgląd w zachowanie użytkowników. Uważamy że systemy komputerowe, z racji działania w nich wielu programów które wpływają wzajemnie na siebie, mają charakter nieliniowy. Dlatego też spośród wielu istniejących metod analizy dużych zbiorów danych zdecydowaliśmy się na użycie nieliniowych metod analizy. Artykuł przedstawia wykorzystanie nieliniowych metod w celu wykrycia subtelnych zmian wprowadzonych do systemu poprzez działanie użytkownika. Analiza skupia się na porównaniu systemu bezczynnego i takiego w który działają programy uruchomione przez użytkownika. Jako zmienna najlepiej charakteryzująca system została wybrana liczba przerwań na sekundę. Artykuł przedstawia użycie wykresu recurrence plot w celu wykrycia podobieństw w zachowaniu systemu, a przez to w działaniu użytkownika. Badanie systemu wykorzystuje serię wykresów aby wykryć charakter zmian wprowadzonych przez użytkownika. Analiza długości pionowych i ukośnych linii pozwala na wykrycie okresowych zachowań komputera, a tym samym na lepsze zrozumienie procesów zachodzących w całym systemie. Pokazane zostało że różne zadania (transmisja danych przy użyciu sieci komputerowej, nagrywanie plików na dysk CD, odczyt plików z dysku DVD, kompresja danych) generuja˛ różne wykresy recurrence plot. Ponieważ zmiany stanu systemu nie znajdują odzwierciedlenia w sygnale przedstawiającym liczbę przerwań na sekundę, użycie recurrence plot jest kluczowe do wykrycia zmian spowodowanych przez użytkownika.