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Search Results: 1 - 10 of 203325 matches for " P. Karasiński "
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TiO2 and SiO2 layer deposited by sol-gel method on the Ti6Al7Nb alloy for contact with blood
W. Walke,Z. Paszenda,P. Karasiński,J. Marciniak
Archives of Materials Science and Engineering , 2012,
Abstract: Purpose: The study contains the analysis of TiO2 and SiO2 surface modification impact on physical and chemical characteristics of Ti-6Al-7Nb alloy samples in the solution simulating cardiovascular system.Design/methodology/approach: Sol-gel coatings were selected on the ground of data taken from literature. The base of stock solution consisted of silicon dioxide precursor SiO2 (TEOS) and titanium oxide precursor TiO2. Application of SiO2 and TiO2 coating on the surface of Ti alloy was preceded by mechanical working – grinding (Ra = 0.40 μm) and mechanical polishing (Ra = 0.12 μm). Corrosion resistance tests were performed on the ground of registered anodic polarisation curves and Stern method. Electrochemical Impedance Spectroscopy (EIS) was also used in order to evaluate phenomena taking place on the surface of the tested alloys. The tests were made in artificial blood plasma at the temperature of T = 37.0±1°C and pH = 7.0±0.2.Findings: Test results obtained on the ground of voltamperometric and impedance tests showed that electrochemical characteristics of Ti-6Al-7Nb alloy differs relative to the type of surface treatment. Practical implications: Potentiodynamic and EIS studies of corrosion resistance in artificial plasma enable to predict the behavior of modified Ti-6Al-7Nb implants in cardiovascular system. The topic proposed in the article is favourable for the development of entrepreneurship sector due to high demand on such technologies and relatively easy implementation of obtained laboratory test results in the industrial and clinical practice.Originality/value: Suggestion of proper surface treatment variants that incorporate sol-gel method is of perspective significance and will help to develop technological conditions with specified parameters of oxide coating creation on the surface of metallic implants.
SAWA experiment – properties of mineral dust aerosol as seen by synergic lidar and sun-photometer measurements
A. E. Kardas,K. M. Markowicz,S. P. Malinowski,G. Karasiński
Atmospheric Chemistry and Physics Discussions , 2006,
Abstract: We propose a method of retrieving basic information on mineral dust aerosol particles from synergic sun-photometer and multi-wavelength lidar measurements as well as from the observations of lidar light depolarisation. We use this method in a case study of mineral dust episode in Central Europe. Lidar signals are inversed with a modified Klett-Fernald algorithm. Aerosol optical depth measured with the sun-photometer allows to reduce uncertainties in the inversion procedure through which we estimate vertical profile of aerosol extinction. Next we assume that aerosol particles may be represented by ensemble of randomly oriented, identical spheroids. Having calculated vertical profiles of aerosol extinction coefficients for lidar wavelengths, we compute the profiles of local Angstrom exponent. We use laser beam depolarisation together with the calculated Angstrom exponents to estimate the shapes (aspect ratios) and sizes of the spheroids. Numerical calculations are performed with the transition matrix (T-matrix) algorithm by M. Mishchenko. The proposed method was first used during SAWA measurement campaign in Warsaw, spring 2005, to characterise the particles of desert dust, drifting over Poland with a southern-eastern wind (13–14 April). Observations and T-matrix calculations show that mode radii of spheroids representative for desert aerosols' particles are in the range of 0.15–0.3 μm, while their aspect ratios are lower than 0.7 or larger than 1.7.
Investigation of geosynthetic interlayer bonding in asphalt layers
P. Zieliński
Archives of Civil Engineering , 2011, DOI: 10.2478/v.10169-011-0029-x
Abstract: The paper presents the results of an extensive investigation of asphalt concrete specimens with geosynthetic interlayer. The subject of this research is evaluation of influence of geosynthetics interlayer applied to bituminous pavements on interlayer bonding of specimens. The results of the tests proves that when geosynthetic is used, the bonding of interlayer depends mainly on the type of bituminous mixture, the type of geosynthetic, and the type and amount of bitumen used for saturation and sticking of geosynthetic. The amount of bitumen used in order to saturate and fix the geosynthetic significantly changes the interlayer bonding of specimens.
Computer modelling and analysis of microstructures with fibres and cracks
P. Fedeliński
Journal of Achievements in Materials and Manufacturing Engineering , 2012,
Abstract: Purpose: The aim of the research is to formulate the boundary element approach, develop the computer codes and analyze microstructures containing fibres and cracks. The computer codes can be used to analyze influence of fibres and cracks on stress fields and effective properties of materials.Design/methodology/approach: The relation between boundary displacements and tractions is established by using appropriate boundary integral equations. The variations of boundary coordinates, displacements and tractions are interpolated by using nodal values and shape functions. Additionally, equations of motion and equilibrium equations are applied for rigid fibres.Findings: The boundary element method can be simply and effectively used for materials containing fibres and cracks. The stress fields for a single fibre computed by the present approach agree very well with analytical results. The fibre, which is perpendicular to the crack has larger influence on stress intensity factors than the fibre, which is parallel to the crack.Research limitations/implications: The proposed method is efficient for linear elastic materials. For other materials the boundary element method requires fundamental solutions, which have complicated forms. The developed computer codes can be extended to materials containing many randomly distributed fibres and cracks.Practical implications: The present method can be used to analyze and optimize strength and stiffness of materials by a proper reinforcement by fibers.Originality/value: The original value of the paper is the analysis of influence of distribution of rigid fibres on effective properties of composites and the influence of positions of a fibre and a crack on stress intensity factors.
On a generalization of the Cartwright-Littlewood fixed point theorem for planar homeomorphisms
Jan P. Boroński
Mathematics , 2015,
Abstract: We prove a generalization of the fixed point theorem of Cartwright and Littlewood. Namely, suppose $h : \mathbb{R}^2 \to\mathbb{R}^2$ is an orientation preserving planar homeomorphism, and let $C$ be a continuum such that $h^{-1}(C)\cup C$ is acyclic. If there is a $c\in C$ such that $\{h^{-i}(c):i\in\mathbb{N}\}\subseteq C$, or $\{h^i(c):i\in\mathbb{N}\}\subseteq C$, then $C$ also contains a fixed point of $h$. Our approach is based on Morton Brown's short proof of the result of Cartwright and Littlewood. In addition, making use of a linked periodic orbits theorem of Bonino we also prove a counterpart of the aforementioned result for orientation reversing homeomorphisms, that guarantees a $2$-periodic orbit in $C$ if it contains a $k$-periodic orbit ($k>1$).
Calculation of atomic spontaneous emission rate in 1D finite photonic crystal with defects
A. Rudziński,P. Szczepański
Physics , 2009, DOI: 10.2478/s11534-010-0001-4
Abstract: We derive the expression for spontaneous emission rate in finite one-dimensional photonic crystal with arbitrary defects using the effective resonator model to describe electromagnetic field distributions in the structure. We obtain explicit formulas for contributions of different types of modes, i.e. radiation, substrate and guided modes. Formal calculations are illustrated with a few numerical examples, which demonstrate that the application of effective resonator model simplifies interpretation of results.
Reliability modeling in some elastic stability problems via the Generalized Stochastic Finite Element Method
M. Kamiński, P. wita
Archives of Civil Engineering , 2011, DOI: 10.2478/v.10169-011-0020-6
Abstract: The main idea of this work is to demonstrate an application of the generalized perturbation-based Stochastic Finite Element Method for a determination of the reliability indicators concerning elastic stability for a certain spectrum of the civil engineering structures. The reliability indicator is provided after the Eurocode according to the First Order Reliability Method, and computed using the higher order Taylor expansions with random coefficients. Computational implementation provided by the hybrid usage of the FEM system ROBOT and the computer algebra system MAPLE enables for reliability analysis of the critical forces in the most popular civil engineering structures like simple Euler beam, 2 and 3D single and multi-span steel frames, as well as polyethylene underground cylindrical shell. A contrast of the perturbation-based numerical approach with the Monte-Carlo simulation technique for the entire variability of the input random dispersion included into the Euler problem demonstrates the probabilistic efficiency of the perturbation method proposed.
A method for estimation of enzymatic browning and its suppression in apple slices
A. Kuczy?…??ski,P. Varoquaux
International Agrophysics , 1996,
Abstract: A described method is based on diffuse light reflectance in the spectral region 400-720 nm for the examination of enzymatic browning of apple slices. In this method apples are sliced as directly dipped for 4 s in the inhibitors. Based on the obtained results data for the limits of visual acceptance of the slice colour are proposed. An enzymatic browning parameter of the slices is determined from the time-course measurements of the difference in absorbance at 440 nm between the brown slice and the same slice where the original colour was restored by slicing a further 1.5 mm layer. Three varieties of apples Granny Smith, Golden Delicious and Red Delicious were sliced under water or in ascorbic acid, oxalic acid and sodium bisulphite solutions. Different concentrations of the suppressant were objectively compared, and their efficiencies were expressed by the allowable period of cold storage.
Precipitation of carbides in Cr – Mo – V cast steel after service and regenerative heat treatment
G. Golański,P. Wieczorek
Archives of Foundry Engineering , 2009,
Abstract: The paper presents results of research on precipitation processes in chromium – molybdenum – vanadium cast steel. Theexamined material was the following cast steel grade: L21HMF and G17CrMoV5 – 10 (L17HMF) after long-term operation at elevatedtemperatures and after regenerative heat treatment. Identification of precipitates was performed by means of the transmission electronmicroscope using carbon extraction replicas and thin foils. On the basis of identifications it has been proved that in the structure ofinvestigated cast steel grades, degraded by long-term operation, there are a few sorts of carbides with diverse stability, such as: M3C; M2C, M23C6, MC, M7C3. Moreover, the occurrence of compound complexes of precipitates – the so called “H-carbides” – has been revealed. Heat treatment of the examined cast steels contributed to changes in morphology and precipitation type. Whilst in the bainitic structure, obtained through heat treatment, only the occurrence of carbide types, such as: M3C; M23C6 and MC has been noticed.
Electron microscopy investigation of the Cr – Mo – V cast steel
G. Golański,P. Wieczorek
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: Investigation of low alloy Cr–Mo–V cast steel after long – term operation and regenerative heat treatment.Design/methodology/approach: Micro structural investigations were carried out using transmission electronmicroscopy.Findings: The microstructure and carbide types after long – term operation and after regenerative heat treatment(including bainitic hardening with high tempering temperature) of Cr–Mo–V cast steel have been presented.Practical implications: : has been shown here is the influence of long term operation and regenerative heattreatment on the structure of Cr–Mo–V cast steel.Originality/value: The paper presents influence of regenerative heat treatment – bainitic hardening withtempering – on the structure of G21CrMoV4 – 6 (L21HMF) cast steel after long - term operation.
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