Raman intensity: An important tool to study the structure and phase transitions of amorphous/crystalline materials

The measurements of the Raman intensity are used mainly to determine quantitatively the amount, distribution and degree of crystallisation of different phases in a material, i.e. the Raman mapping. Our studies reveal that the analysis of relative and absolute Raman intensity is a very powerful tool, which allows to investigate and characterize the modifications of the structure in covalent bonded compounds, e.g. due to: (i) changes of BO₆ octahedra by the substitution of the B site by lanthanides or rare earth elements and the incorporation of protons in the case of high temperature protonic conductors, (ii) changes of the long range order correlations as the function of the nanoregion organization: continuous evolution of the local symmetry towards the long range cubic one in the case of PbMg_1/3Nb_2/3O₃–xPbTiO₃ (PMN–PT) relaxor ferroelectrics, (iii) changes of the Si–O network caused by the depolymerisation resulting from the substitution of the Si⁴⁺ ions (covalent bonds) by the M⁺ cations (ionic bonds) or by the incorporation of the metallic nanoprecipitates and (iv) changes caused by the lixiviation/protonation of the surface layers of the Cultural Heritage stained glasses as a function of their corrosion degree and age.     

Comparison of Lupinus angustifolius protein digestibility in dependence on protein,amino acids,trypsin inhibitors and polyphenolic compounds content

Lupine seeds are proposed as a source of valuable protein in human and animal nutrition. However, not only protein content but its bioavailability is important. Thus, the protein digestibility of twenty Lupinus angustifolius varieties seeds and the impact of some factors (protein and polyphenols content, trypsin inhibition and amino acids composition) on the protein digestion were discussed. Composition as well as the digestibility of these seeds was influenced by variety, weather conditions (precipitations) and place of cultivation (soil quality). The average digestibility of the seeds was 46%. The positive impact on the digestibility had the extractivity of the protein. Higher than it was expected activity of trypsin inhibitors (even up to ~32%) in some varieties influenced the protein availability, while the lysine and phenolic compounds content did not affect digestibility. The content of compounds influencing protein digestibility depends both on variety as well as on agronomical conditions.     

Organosilicon resin-based carbon/ceramic polygranular composites with improved oxidation resistance

We examined the thermo-mechanical properties of carbon materials modified with silicon oxycarbide (Si-O-C) and silicon carbide (Si-C). These compounds were obtained by the impregnation of carbon components with a silicon-containing polymer resin. Graphite and anthracite powders were used as carbon components, and poly[methyl(phenyl) siloxane] resin (P) was used as the ceramic precursor. Carbon/polymer compositions (C/P) were subjected to two-stage annealing, first to 1,000 °C and next to 2,000 °C in an inert atmosphere, leading to the formation of C/Si-O-C and C/Si-C composite samples, respectively. The materials were then examined under conditions of isothermal oxidation to determine their oxidation resistance and the mechanical properties before and after oxidation tests. The structure of the samples before and after oxidation was studied. C/Si-C composites, despite their high porosity, proved to have enhanced resistance to oxidation at 600 °C, although they had lower mechanical properties in comparison to C/Si-O-C samples.     

Electrical and mechanical properties of granular-fibrous carbon-carbon composites with recycled carbon fibres

In the following study, the electrical and mechanical properties of granular-fibrous carbon-carbon composites with short recycled carbon fibres have been investigated. The examined composites contained from 0 to 12?wt% of three types of recycled carbon fibres that differ in length. The conducted study has proven that it is not the type of applied fibre, but rather the resultant porosity of composites that exerts the predominant influence on the electrical resistivity and mechanical properties of the tested materials. The curve fitting revealed mathematical formulas correlating the studied properties with the apparent density of the composite samples. Owing to the addition of the shortest carbon fibres, the mechanical and electrical properties were significantly improved (50.14% and 24.06% increase in modulus of elasticity and flexural strength respectively for the sample with 12?wt% of the shortest fibres). A 21.39% decline in the resistivity ($?=161.26\mu \Omega ?\mathrm{m}$) of the composite containing 4% of shortest fibres was noted in comparison with the reference sample. Unlike powdered fibres, the addition of longer fibres caused an increase in porosity and deterioration of microstructure, which resulted in a significant decline in the key properties of the investigated composites.     

Hot corrosion behaviour of Ni3Al in sulphate-chloride mixtures in the atmosphere

Hot corrosion of Ni₃Al intermetallic compound in the presence of sulphate-chloride mixtures was studied. A comminuted Ni₃Al mixed with NaCl-Na₂SO₄, NaCl-Li₂SO₄, LiCl-Na₂SO₄, LiCl-Li₂SO₄ additions was oxidized in the air up to 1000 °C with linearly increasing temperature and isothermally within the temperature range of 500-700 °C. The corrosion process was observed by thermogravimetric method using Mettler thermoanalyzer.The experiments indicated that LiCl (∼10 wt.%)-Li₂SO₄ mixture was the most corrosive agent. It was also found that by addition of MgO the corrosion of Ni₃Al was reduced. Phase composition of the corrosion products was established by X-ray diffraction analysis; there were detected Al₂O₃, Al₂S₃, NaAlO₂ (or LiAlO₂) as intermediate products, nickel sulphides, NiO and NiAl₂O₄. NiAl₂O₄ spinel was formed only at the highest temperatures, while at lower temperatures alumina was present instead of spinel.Hot corrosion behaviour of Ni₃Al in sulphate-chloride mixtures in air atmosphere.     

Features Extraction for Detection of Blurred Image Regions

The article discusses our study of the problem of blurred image regions detection. Proposed are 21 features: 20 based on the discrete wavelet transform and one being a ratio based on a gray-level co-occurrence matrix. Described features are introduced in order to detect blurred segment regardless of the blur type such as background blur, motion blur, or out of focus. Moreover, proposed features are relatively easy to calculate and parallelize. Multilayer perceptron with a backpropagation algorithm is trained on mentioned features. Three approaches are introduced and tested: (1) with nonoverlapping fixed size windows, (2) with nonoverlapping recursively divided windows, and (3) with addition of a morphological closing operator.     

Influence of laser heat treatment on microstructure and properties of surface layer of Waspaloy aimed for laser-assisted machining

In this study, a nickel-based superalloy, Waspaloy, was laser heat treated with diode laser. Single laser tracks were manufactured with different laser beam power densities between 63 and 331 kW/cm², and scanning laser beam speed ranged from 5 to 100 m/min. It was found that laser heat treatment of Waspaloy causes decrease in material hardness—the microhardness in laser tracks is about 300 HV0,1 while the microhardness of substrate is ranged from 300 to 600 HV0,1—which is a positive phenomenon for laser-assisted machining of investigated material. Impacts of laser heat treatment parameters on laser tracks properties were identified for obtaining multiple laser tracks with the most homogenous thickness. Moreover, roughness of heated layers was measured to specify surface quality after laser heat treatment. Multiple laser tracks were produced using different scanning laser beam speed and distances between laser tracks ranged from 0.125 to 1 mm. It was found that if scanning laser beam speed is 75 m/min and distance between laser tracks is equal to or lower than 0.25 mm, in microstructures of multiple laser tracks, cracks are occurring. The most suitable laser heat parameters for obtaining heated layers, and which can be used for laser-assisted machining, were identified as laser beam power density 178.3 kW/cm², scanning laser beam speed 5 m/min, and distance between laser tracks 0.125 mm.     

Enhancement of oxygen reduction by incorporation of heteropolytungstate into the electrocatalytic ink of carbon supported platinum nanoparticles

Nafion stabilized inks of Vulcan XC-72 supported platinum (20 wt.%) nanoparticles (Pt/XC-72) were utilized to produce electrocatalytic films on glassy carbon. The catalysts were modified (activated) with phosphododecatungstic acid H₃PW₁₂O₄₀ (PW₁₂). Comparison was made to bare (PW₁₂-free) electrocatalytic films. Electroreduction of dioxygen was studied at 25 °C in 0.5 mol dm⁻³ H₂SO₄ electrolyte using rotating disk voltammetry. For the same loading of platinum (≈95 μg cm⁻²) and for the approximately identical distribution of the catalyst, the reduction of oxygen at a glassy carbon electrode modified with the ink containing PW₁₂ proceeded at ca. 30-60 mV more positive potential (depending on the PW₁₂ content), and the system was characterized by a higher kinetic parameter (rate of heterogeneous electron transfer), when compared to the PW₁₂-free electrocatalyst. Gas diffusion electrodes with Pt/XC-72 supported on carbon paper (Pt loading 1 mg cm⁻²) were also tested. Under the same experimental conditions, while the exchange current density and the total resistance contribution to polarization components, computed from the galvanostatic polarization curves were found to be clearly higher and lower, respectively, for the ink modified with PW₁₂ relative to the unmodified system. The results demonstrate that addition of heteropolytungstatic acid (together with Nafion) enhances the electrocatalytic activity of platinum towards reduction of oxygen.     

Psychological Determinants of Using Facebook: A Research Review

In recent years, Facebook has become the most popular of social networking sites (SNSs). Due to its increasing popularity and rising number of its users, the phenomenon of Facebook has aroused academic interest as well. There has been a growing number of studies on this subject. The aim of this article is to present the main trends in Facebook research and to provide an overview of major empirical findings. Among the most intensively explored topics in Facebook research, studies that concentrate on personality and individual differences among users, the role of self-efficacy, and motivation for using that specific SNS were identified. There is also a growing trend in empirical studies that focuses on testing advanced theoretical models of Facebook usage determinants. Technology acceptance model, presented in this article, is one of the most often used among them. This kind of approach may serve as a suggestion for a methodological conceptualization in the future confirmatory research on Facebook.     

Hygroscopic Behavior of Aerosol Particles Emitted from Biomass Fired Grate Boilers

This study focuses on the hygroscopic properties of submicrometer aerosol particles emitted from two small-scale district heating combustion plants (1 and 1.5 MW) burning two types of biomass fuels (moist forest residue and pellets). The hygroscopic particle diameter growth factor (Gf) was measured when taken from a dehydrated to a humidified state for particle diameters between 30–350 nm (dry size) using a Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA). Particles of a certain dry size all showed similar diameter growth and the Gf at RH = 90% for 110/100 nm particles was 1.68 in the 1 MW boiler, and 1.5 in the 1.5 MW boiler. These growth factors are considerably higher in comparison to other combustion aerosol particles such as diesel exhaust, and are the result of the efficient combustion and the high concentration of alkali species in the fuel. The observed water uptake could be explained using the Zdanovski-Stokes-Robinson (ZSR) mixing rule and a chemical composition of potassium salts only, taken from ion chromatography analysis of filter and impactor samples (KCl, K₂SO₄, and K₂CO₃). Agglomerated particles collapsed and became more spherical when initially exposed to a moderately high relative humidity. When diluted with hot particle-free air, the fractal-like structures remained intact until humidified in the H-TDMA. A method to estimate the fractal dimension of the agglomerated combustion aerosol and to convert the measured mobility diameter hygroscopic growth to the more useful property volume diameter growth is presented. The fractal dimension was estimated to be ～ 2.5.