The Slenderness Ratio of the Filter Used in the Process of Liquid Steel Filtration as the Additional Parameter of the Filter Form

We propose in this publication the introduction of new, additional definition describing the multiple orifice ceramic filters used in research works on the liquid steel filtrations, calling this the filter slenderness ratio. In order to confirm the theoretical assumptions we have performed a series of the laboratory scale experiments (for the filter slenderness ratio S_F1 λ = 1.67 and S_F2 λ = 3.34). The influence of the filter slenderness on the filtration process efficiency has been determined through variations in quantities and surface shares of the non‐metallic inclusions in the filtrated steel in relation to the non‐filtered steel. We present also the results of researches on the separating surfaces between the liquid steel and the ceramic filter material, which in form of photos and scanning microscope microanalyses are put together in the publication.     

The effect of biomass co-combustion in a CFB boiler on solids accumulation on surfaces of P91 steel tube samples

The paper describes the results of industrial tests associated with the co-combustion of biomass and agromass with coal and focused on diagnostics and assessment of the effect of fuel type on the accumulation of solids on the surface of P91 steel tube samples placed in the vicinity of steam superheater in a commercial large-scale (over 400 MW) circulating fluidized bed boiler.Analysis of samples indicated the effect of fuel type, as well as the location of the area on the steel tube on the rate of solids accumulation. Alkali compounds were quite uniformly distributed at both front and rear sections of the steel tube samples, while calcium and sulfur components were mainly found in the front area. The average solids accumulation rates calculated for the rear areas of P91 steel tube samples were roughly two times higher than those for the front ones. The highest solids accumulation rate on the front area (1.04·10⁻⁹ ms⁻¹) was calculated for the case of agromass co-combustion with coal.     

On application of input data partitioning to Bayesian weighted averaging of biomedical signals

Averaging in the time domain may be used for noise attenuation in case of biomedical signals with a quasi‐cyclical character. Traditional arithmetic averaging technique assumes the constancy of the noise power cycle‐wise, however, most types of noise are not stationary and the variability of noise power is observed. It constitutes a motivation for using methods of weighted averaging, in particular Bayesian weighted averaging. This paper presents the computational study of Bayesian weighted averaging with traditional (sharp) and fuzzy partition of the input data in the presence of non‐stationary noise. There is presented the known empirical Bayesian weighted averaging method (EBWA), with the parameter p describing the probabilistic model, and its modification NBWA which eliminates the parameter. Both methods can be extended by partitioning of the input data. The performance of presented methods is experimentally evaluated for an analytical signal as well as a real ECG signal and compared with traditional arithmetic averaging method. However, the methods can be applied to any signal with a quasi‐cyclical character. The aim of the paper is to show the influence of the type of partition as well as the number of parts on the quality of the averaged signal.     

2-Methyltetrahydrofuran: Sustainable solvent for ruthenium-catalyzed olefin metathesis

Applicability of 2-methyltetrahydrofuran for olefin metathesis was examined with a set of ruthenium Hoveyda-type second generation catalysts. Influence of temperature was studied and the results were compared with those obtained in classical solvents for metathesis: dichloromethane and toluene.     

Synthesis and investigation of monomodal hydroxy-functionalized PEG methacrylate based copolymers with high polymerization degrees. Modification by “grafting from”

The synthesis of monomodal copolymers with poly(ethylene glycol) (PEG) side chains from commercial poly(ethylene glycol) methacrylates (PEGMA) by atom transfer radical polymerization (ATRP) is verified. Two hydroxy-functionalized PEGMA macromonomers (520 g/mol and 360 g/mol) were copolymerized with methyl methacrylate (MMA) using various initial feed (1.5/98.5–50/50 mol.%). The copolymers P(MMA-co-PEGMA) with high degree of polymerization, e.g. 100–275 of repeating units in the backbone including 7–56 PEG side chains, were obtained. The relative reactivity ratios of PEGMA and MMA determined by the Jaacks method indicated slightly faster incorporation of macromonomer into polymeric chain than MMA (r_MMA = 0.79; r_PEGMA = 1.27). The polymers containing at least 17 mol.% of PEGMA units were water-soluble and exhibited clouding point at temperature in a broad range of 39–70 °C. The temperature-sensitive effect makes these polymers as a potential carriers in drug delivery systems. In the case of copolymers insoluble in water, a three-step procedure, including esterification to ATRP multifunctional macroinitiators, ATRP of tert-butyl methacrylate (tBMA) by grafting from, deprotection of carboxylic groups by removing tert-butyl groups, was applied to extend PEG grafts and expand the content of hydrophilic fraction (32–94 mol.%), what efficiently developed polymer solubility in polar solvents giving possibility for the future biomedical applications.     

Wavelet transform-based stress-time history editing of horizontal axis wind turbine blades

Full scale blade fatigue testing is required to verify that the horizontal axis wind turbine (HAWT) blades posses the strength and service life specified in the design. Unfortunately, fatigue tests must be run for a long time period, which has led blade testing laboratories to seek ways of accelerating fatigue testing time and reducing the costs of tests. The objective of this article is to develop a novel method called a WT-based fatigue damage part extracting method. Based on wavelet transform (WT), this method extracts fatigue damage parts from the stress-time history and generates the edited stress-time history with shorter time length. Also, this article proposes a concept of applying accumulative power spectral density (AccPSD) to identify fatigue damage events contained in the stress-time history of HAWT blades. Wavelet functions used in this study are Morl, Meyr, Dmey, Mexh and DB30. It has been found that Mexh wavelet with an AccPSD level of 9000 Energy/Hz provides the edited stress-time history having a maximum reduction of 20.77% in length with respect to the original length, whilst fatigue damage per repetition can be retained almost the same as the original one. In addition, an existing method, time correlated fatigue damage (TCFD), is used to validate the effectiveness of a WT-based fatigue damage part extracting method. The results suggest that not only does the WT improve the accuracy of fatigue damage retained, but also it provides a shorter length of the edited stress-time history. To conclude, WT is suggested as an alternative technique in fatigue durability study, especially for the field of wind turbine engineering.     

Changes of fluorescent spectral features after successive rare earth doping of gadolinium oxide powders

We present a complex fluorescence study of a series of gadolinium oxide polycrystalline powders singly, doubly and triply doped with trivalent rare earth ions (Er³⁺, Tb³⁺, and Dy³⁺), to explore a possibility of their use as materials for white light emitting diodes. The excitation and luminescence spectra along with the decay kinetics were measured in the temperature range from 6 to 300 K. The luminescence efficiency was studied within the visible spectral range, i.e. −400 nm to 750 nm under excitation by 355 nm third harmonic Nd:YAG laser pulses. Singly doped Er³⁺ sample gave stronger luminescence signals, but others showed significantly larger decay lifetimes. The successive rare earths doping leads to substantial changes of the spectral positions due to the up-conversion processes. In the singly (Er³⁺) doped sample, following the time resolved spectrum and decay curves, there are two different types of emissions: at 660 nm and at shorter wavelengths (below 640 nm) the red emission's lifetime is ten times longer than at shorter wavelengths. The singly doped sample shows unclear temperature-dependence of luminescence with lifetime at 550 nm (the longest at 100 K, similarly at 6 K and 300 K) and achieved luminous efficacy 73.5 lm/W.     

Intermetallic powders of Ni–Al, Cu–Al and Cr–Al systems obtained by the self-disintegration method

The intermetallic compounds of the Ni–Al, Cu–Al and Cr–Al systems are characterised by the profitable set of mechanical and physical properties, such as good abrasion resistance, high temperature oxidation and sulfur corrosion resistance.

Alloy powders, among them intermetallic powders, are widely used and methods of their production are under development. The technology described here takes advantage of a natural phenomenon, i.e. self-disintegration which takes place in alloys containing Al₄C₃ carbide, e.g. in high aluminium cast iron. The result of chemical reaction between this carbide and moisture are products of bigger volume. It causes cracking of the matrix, i.e. self-disintegration into a powder. The physical–chemical principles of the powder production using self-disintegration are presented in this article.

In Ni–Al–C, Cu–Al–C and Cr–Al–C alloys, Al₄C₃ phase is not present in the liquid melt. Therefore, the presence of a catalysing component, increasing the chemical activity of carbon, is required. Iron can be one of such additions. The mechanism of the influence of the iron on the Al₄C₃ carbide crystallisation and the physical–chemical properties of the powders obtained by the self-disintegration process is presented in this work. Applications (plasma spraying, powder metallurgy) of the intermetallic powders obtained in this way are mentioned.