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1

Pomiary trajektorii iskry długiej w przestrzeni trójwymiarowej

Molasy Michał, Szewczyk Marcin

Przegląd Elektrotechniczny

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2022

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R. 98, nr 10

181--184

PL

W artykule przedstawiono zagadnienia związane z pomiarami laboratoryjnymi trajektorii iskry długiej dla udarów piorunowych i łączeniowych o biegunowości dodatniej i ujemnej. Przedstawiono układ eksperymentalny umożliwiający wykonanie pomiarów iskry długiej w układach wysokonapięciowych kula-płyta oraz kula-kula, jak również w układach modelowych odzwierciedlających zjawisko przeskoku wzdłuż łańcucha izolatorowego. Opisana metoda badawcza może być również wykorzystana do prowadzenia pomiarów w układach wieloelektrodowych. Przedstawiony układ pomiarowy i sposób wykonania pomiarów iskry długiej umożliwiają wyznaczenie parametrów trajektorii wyładowań, co może zostać użyte do opracowania i weryfikacji modeli symulacyjnych wyładowań iskrowych z wykorzystaniem modelowania fraktalnego.

EN

The article presents aspects related to laboratory measurements of a long spark trajectory for lightning and switching strokes with positive and negative polarity. The paper presents an experimental setup that enables long spark measurements in conventional sphere-plate and spheresphere high-voltage systems, as well as in model systems reflecting the phenomenon of a discharge along the insulator chain. The described method can also be used to conduct measurements in multi-electrode systems. The presented measuring system and the method of long spark measurements make it feasible to determine the parameters of the discharge trajectory, which can be used to develop and validate the simulation models of spark discharges with the use of fractal modeling.

2

Fractal model of transdermal drug delivery

Walicka A., Iwanowska-Chomiak B.

International Journal of Applied Mechanics and Engineering

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2018

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Vol. 23, no. 4

989--1004

EN

Skin, separating the vital organs of a human body, is a desirable route for drug delivery. However, the intact skin is normally permeable only for drug molecules with a low molecular weight. The stratum corneum (SC), being the outermost layer of the skin and the epidermis being the second – more permeable – layer of the skin, play an essential function in transdermal drug delivery. Physical and chemical methods of skin poration are used to enhance transdermal drug delivery. Each poration leads to an irregular system of pores which are connected with a system of micro-capillaries passing through the epidermis. Both the systems by their irregularity form a fractal porous matrix. Drugs administrated by this matrix can be either suspensions and solutions or creams and gels, therefore they have to be modelled as non-Newtonian fluids. To analyse the fluid flow through the porous matrix the model of the epidermis is assumed as gobbet-andmortar with the tortuous mortar of variable thickness and after transition from the mortar to the tube one considered classical and fractal capillary flows of selected non-Newtonian fluids. Fractal expressions for the flow rate, velocity and permeability of fluids flow in a porous matrix are derived based on the fractal properties of the epidermis and capillary model. Each parameter in the proposed expressions does not contain any empirical constant and has a clear physical meaning and the proposed fractal models relate the flow properties of considered fluids with the structural parameters of the epidermis as a porous medium. The presented analytical expressions will help understand some of the physical principles of transdermal drug delivery.

3

Investigation of copper and gold prospects using index overlay integration method and multifractal modeling in Saveh 1:100,000 sheet, Central Iran

Rezaei S., Lotfi M., Afzal P., Jafari M. R., Meigoony M. S., Khalajmasoumi M.

Gospodarka Surowcami Mineralnymi

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2015

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T. 31, z. 4

51--73

EN

This study aims at prospecting copper and gold promising areas in Saveh 1:100,000 sheet, situated in Urumieh-Dokhtar magmatic belt (Central Iran). Geographic information system (GIS) is effective in recognition of probable mineral resources by collecting, processing, exploration layer weighting and integrating thematic maps. As there is no certainty in different geological phenomena, modeling and integrating information layers are used to obtain suitable results for determining potential areas. In this study, index overlay method, which is a combination of software processing and expertise knowledge, was used. The survey layers consist of the lithologic units, geophysical data, mineralization, faults and structures and alteration. [...]

PL

Badanie to ma na celu poszukiwanie miedzi i złota z perspektywicznych obszarów w Saveh na arkuszu 1:100 000, położonego w pasie magmowym w Urumieh-Dokhtar (Centralny Iran). System informacji geograficznej (GIS) jest skuteczny w rozpoznaniu przypuszczalnych zasobów surowców mineralnych poprzez gromadzenie, przetwarzanie warstwy ważenia poszukiwań i integracji map tematycznych. W celu uzyskania właściwych wyników dla potrzeb określenia potencjalnych obszarów do eksploatacji, użyto techniki modelowania i zintegrowanej informacji o warstwach geologicznych. W tym badaniu została użyta metoda wskaźnikowa, która jest kombinacją komputerowego sposobu przetwarzania danych i wiedzy eksperckiej. Badane warstwy geologiczne opisane są pojęciami litologicznymi, danymi geofizycznymi, stopniem mineralizacji oraz zaburzeniami tektonicznymi. [...]

4

Normal contact stiffness of fractal rough surfaces

Buczkowski R., Kleiber M., Starzynski G.

Archives of Mechanics

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2014

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Vol. 66, nr 6

411–-428

EN

We used the fractal theory based on a single variable Weierstrass–Mandelbrot function to obtain the normal contact stiffness if rough and smooth isotropic surfaces are pressed against each other. Because in the original fractal theory the distribution of contact area is assumed geometrically, we propose the method in which the actual deformation of asperities and a correction due to asperity coupling (interaction) will be taken into account. This correction is equivalent to an increase of the effective separation by a quantity proportional to the nominal pressure and it has a significant effect on contact stiffness at larger normal loads (low separations). The numerical results demonstrate a nonlinear evolution of the contact stiffness with the normal load in particular in the first stage of loading at low squeezing pressures. We have compared the results of the theoretical contact stiffness using the fractal method with the experimental ultrasonic measurements. Experimental results made on real surfaces agree remarkably well with the theoretical predictions.

5

Analysis of pores in pig meat images

Ballerini L., Bocchi L., Hullberg A.

Machine Graphics and Vision

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2004

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Vol. 13, No. 1/2

137-148

EN

In this paper we present an image processing application for quantification of pores in pig meat images. The aim is to study the relationship between the number and size distribution of pores and process condition and genotype. We used digital camera photographs of slices of tumbled and non-tumbled processed pork loins of different RN genotype. We describe a method to extract and count the number and size of pores. We propose a new approach, based on fractal theory, to quantify the size distribution of pores. Our results show that image analysis in conjunction with fractal models can be useful in this field.

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Fractal model of the cold martensite transformation in steels

Rybaczuk M., Ziętek G.

Archives of Civil and Mechanical Engineering

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2002

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Vol. 2, no 2

65-77

EN

The paper proposes an approach employing fractal geometry to describe growing martensite phase in an austenitic steel. Inside macroscopic volume (specimen), the distribution of martensite is depicted by measure, and the scaling properties of this measure describe the important, long scale changes of materi-als characteristics. In fact, distribution of martensite relates to two measures. The first one establishes the mass distribution, and the second one corresponds to additional energy concentrated in martensite phase. The initial postulate consists of specific form of free energy. Besides the uniform material part, it contains also terms coming from each exact-dimensional measure contributing to dimension decomposition of the measure depicting martensite. The final macroscopic constitutive equation becomes some integral over “partial” ones. Calculations make use of the essential simplification – stratification into discrete cells. Various models are studied. Experimental tests were carried for austenitic steel under uniaxial stress states.

PL

Przedstawiono próbę zastosowania geometrii fraktalnej do opisu wzrostu fazy martenzytycznej w stali austenitycznej. Wewnątrz makroskopowej objętości próbki rozkład martenzytu zadaje miara i własności tej miary z uwagi na skalowanie opisują istotne własności materiału w zakresie długich skal. Faktycznie rozkład martenzytu jest związany z dwoma miarami. Pierwsza określa rozkład masy, a druga odpowiada dodatkowej energii skupionej w fazie martenzytycznej. Podstawowy postulat to specyficzna postać energii swobodnej. Oprócz jednorodnego członu związanego z materiałem zawiera ona również człony pochodzące z każdej miary wymiarowego rozkładu miary opisującego rozkład martenzytu. W rezultacie makroskopowe równanie konstytutywne staje się całką po częściowych wkładach. Obliczenia wykorzystują istotne uproszczenie – rozkład na komórki. Zbadano różne modele. Testy eksperymentalne przeprowadzono dla stali austenitycznej w jednoosiowym stanie naprężenia.

7

Fractal sky algorithm

Pietruszka M., Wawrzyniak A.

Journal of Applied Computer Science

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1998

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Vol. 6, nr 1

37-50

EN

The paper presents a simple and fast algorithm based on the midpoint displacement method and applied to modelling and visualisation of a cloudy sky. The use of the parameters given in the paper enables generation of a model common for both sky and mountains, which significantly reduces modelling time.

8

Saxas studies on porous materials.

Pająk L., Jarzębski A.B., Bierska B., Łągiewka E.

Inżynieria Materiałowa

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1998

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R. XIX, nr 4

1191-1194

EN

The structure of most porous materials is quite complex. In the last two decades the characterisation of the structure of these materials 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 structure better than the classical models which assume the existence of macro-, meso- and micropores of simple geometry. Pores are essential in materials applied as catalysts, filters, membranes, adsorbents. Thus the knowledge of the specific surface area, pore size and roughness of pore-solid interface is the prime importance. These parameters in the length scale 5-1000 angstrom can be estimated by the small-angle X-ray scattering (SAXS) method. The SAXS studies were performed on different porous silica materials, zirconia aerogels and metal foils electrodeposited in galvanostatic conditions. The fractal concept was applied to facilitate the interpretation of SAXS results.