Wyniki wyszukiwania - BazTech

1

Fractal analysis of sandstone pore space geometry

Figiel M., Lewandowska-Śmierzchalska J.

AGH Drilling, Oil, Gas

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2018

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Vol. 35, no. 2

377--389

EN

Fractal analysis is currently one of the fastest evolving branches of science. Numerous objects in nature exhibit a fractal structure. Additionally, the vast majority of rocks – especially reservoir rocks – take the form of a fractal. Computer image analysis based on thin-section images has been used for examining the fractal structure of pore spaces, directly applying the definition of the fractal box-counting dimension. For the examined sandstone sample, thin sections were made and photographed, and the corresponding values of the fractal dimension and lacunarity were calculated. Each of the photos was encompassed by porosity that was calculated based on the number of pixels. Furthermore, the volatility of the fractal dimension and lacunarity were studied as well as their relationships with the porosity. A correlation analysis between the fractal parameters and the porosity was carried out. The results were compared with the data obtained from a mercury porosimetry of the same sample of sandstone.

2

Delivery-flow routing and scheduling subject to constraints imposed by vehicle flows in fractal-like networks

Bocewicz G., Banaszak Z., Nielsen I.

Archives of Control Sciences

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2017

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Vol. 27, no. 2

135--150

EN

The problems of designing supply networks and traffic flow routing and scheduling are the subject of intensive research. The problems encompass the management of the supply of a variety of goods using multi-modal transportation. This research also takes into account the various constraints related to route topology, the parameters of the available fleet of vehicles, order values, delivery due dates, etc. Assuming that the structure of a supply network, constrained by a transport network topology that determines its behavior, we develop a declarative model which would enable the analysis of the relationships between the structure of a supply network and its potential behavior resulting in a set of desired delivery-flows. The problem in question can be reduced to determining sufficient conditions that ensure smooth flow in a transport network with a fractal structure. The proposed approach, which assumes a recursive, fractal network structure, enables the assessment of alternative delivery routes and associated schedules in polynomial time. An illustrative example showing the quantitative and qualitative relationships between the morphological characteristics of the investigated supply networks and the functional parameters of the assumed delivery-flows is provided.

3

ICT network traffic based on a simple fractal structure

Włodarski P.

Logistyka

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2011

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nr 6

EN

The results of measurements of ICT network traffic reveals the presence of fractal structures and long-range dependence. Accurate modeling of the offered traffic load is the first step in optimizing resource allocation algorithms and QoS requirements. In this article the fractal structure is represented by the simple random midpoint displacement method which approximates fractional Brownian motion (fBm), theoretical process that exhibits aforementioned features, is presented. Apparently, this algorithm generates inaccurate approximation of fBm for the higher degree of self-similarity. To improve this simple and fast algorithm, some modifications based on variance analysis are proposed. The results of simulation and statistical testing with comparison to the realtime measurements in computer network are presented and discussed.

PL

Wyniki pomiarów natężenia ruchu w sieciach teleinformatycznych ujawniają obecność struktur fraktalnych oraz zależności długoterminowych. Dokładne modelowanie obciążenia stanowi zatem pierwszy krok w optymalizowaniu rezerwacji zasobów sieciowych oraz pomaga spełnić wymagania QoS (Quality of Service). W artykule strukturę fraktalną otrzymano za pomocą metody losowego przemieszczenia środka odcinka, dzięki czemu otrzymano przybliżenie procesu ułamkowego ruchu Browna stanowiącego teoretyczną podstawę w analizie struktur fraktalnych. Jak się okazuje, zaprezentowana metoda niezbyt dokładnie przybliża ten teoretyczny proces, szczególnie dla wyższych stopni samopodobieństwa. Aby ulepszyć tą prostą i szybką metodę zaproponowano pewne modyfikacje bazujące na analizie wariancji. Zaprezentowano wyniki symulacji oraz testowanie statystyczne w zestawieniu porównując je do rzeczywistego ruchu zarejestrowanego w sieci teleinformatycznej.

4

Czy prawa Hortona poprawnie opisują fraktalną strukturę sieci rzecznych?

Bajkiewicz-Grabowska E., Olszewski R.

Przegląd Geofizyczny

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2001

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Z. 3

223-239

EN

The network analysis with application of the Horton-Strahler method can be used in description of river network in draingae basin. The Horton's rations characterized organization of river network. Regularity and even self-similarity of river networks are proved by bifurcation and stream-lenght ratios, so that the structure of river networks can be described by a fractal dimension. The value of fractal dimension is due to estimation method. The analysis of 28 Polish river networks shows the superiority of the box method to the Horton method. It was proved that the estimation algorithm Dr = logRB/logRL based on statistical Horton's ratios doesn't define fractal dimension of the river network correctly. It was also proved that fractal dimension estimating by the box method only to some extent depends on the generalization method.

5

Badanie metodą małokątowego rozpraszania promieni rentgenowskich (SAXS) materiałów porowatych o strukturze fraktalnej

Pająk L., Bierska B., Łągiewka E.

Archiwum Nauki o Materiałach

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1998

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t. 19, nr 1

53-70

PL

Struktura większości materiałów porowatych jest złożona. Porowatość materiałów (część objętości materiałów zajęta przez pory) zmienia się w szerokim zakresie - od poniżej 1% aż do ponad 99%, jak np. w aerożelach. W ostatnim dwudziestoleciu w związku z zastosowaniem geometrii fraktalnej uczyniono znaczny postęp w opisie struktury materiałów porowatych. Modele fraktalne opisują lepiej rzeczywistą strukturę porów niż modele klasyczne, dla których przyjęto istnienie makro-, mezo- i mikroporów o prostych kształtach. Metoda małokątowego rozpraszania promieni rentgenowskich jest szczególnie użuteczna w badaniu struktury materiałów porowatych w skali 10-1000 A. Umożliwia uzyskanie informacji, które są trudno osiągalne, albo w ogóle niedostępne innymi metodami. Możliwości badania materiałów porowatych o strukturze fraktalnej za pomocą metody SAXS przedstawiono na przykładzie aerożeli krzemionkowych i folii miedzianych otrzymanych elektrolitycznie.

EN

The structure of most porous materials is quite complex. The porosity of materials (total volume fraction of material occupied by pores) can vary in a very broad range, from much less than 1% up to more than 99%, in the case of aerogels. In the last two decades the characterization of the structure of porous materials has made a milestone progress owing to the use of fractal geometry. At present it is generally accepted that the fractal models of pore structure describe the real morphology better than the classical models which assume the existence of macro-, meso- and micropores of simple geometry. The SAXS method is specially useful in the studies of porous material in the length scale 10-1000 A. It gives information which is difficult to obtain or even not available by use of other methods. The SAXS studies were performed on silica aerogels and copper foils electrodeposited in galvanostatic conditions. The fractal concept was applied in the interpretation of SAXS results.