Elemental analysis of nutritional preparations by inductively coupled plasma mass and optical emission spectrometry

This paper reports the development and using of ICP-MS and ICP-OES methods for determination of major, minor and trace elements in multivitamin preparations and dietary supplements and, based on results, their classification using multivariate statistical methods.The method was optimised and evaluated with the use of “in-house” reference material, commercial reference materials and spiked samples. Macroelements (Na, K, Ca, Mg, P), microelements (Cu, Fe, Mn, Zn, Se, Cr), toxic elements (As, Cd, Pb, Ni, V) and a whole series of other elements (e.g. REEs, Ti, Au, Pt, Pd, etc.) were detected with excellent limits of detection as well as other procedure parameters suitable for the purpose of the elemental analysis.As for physiologically significant elements, contents were found as follows (mg kg⁻¹): Ca 560-196,000, Mg 308-70,300, Na 289-74,000, K from undetectable to 28,200, Cu 28-1460, P from undetectable to 217,000, Zn 2.1-25,000, Fe 115-39,400, Mn 28-1860, Cr 0.486-26.6, Mo 0.0418-9.88, and Se 0.395-161. It was found out, if compared with recommended daily intakes, that maximally 50% Ca, 37% Mg, 3% K, 20% P, 14% Na, 100% Cu, 160% Mn, 190% Fe, 120% Zn, 24% Cr, 29% Mo and 79% Se can be obtained from one dose. Extreme samples presenting a possible health risk (Ni content nearly 200 mg kg⁻¹) were indicated. Most of the remaining elements (e.g. REEs) were analysed in order to get reference values for nutritional preparation.     

Pretreatment and feeding of biomass for pressurized entrained flow gasification

In our contribution we have compared advantages and disadvantages of four different methods for biomass (wood) thermal pretreatment and grinding for feeding of the biomass-fuel to pressurized entrained flow gasifier. The four methods of pretreatment and feeding involve drying, torrefaction, flash pyrolysis and dissolution of wood in organic solvents.     

Thermal analysis and phase transformation behaviour during additive manufacturing of Ti–6Al–4V alloy

Despite the fact that the additive manufacturing (AM) technique has been established for almost two decades, its optimisation is still performed by trial and error experimentation. In the present work, a finite element modelling approach was used to study both the temperature distribution and heat flux vector characteristics during multi-layer deposition of a Ti–6Al–4V alloy that take place in the AM process. The results revealed the difference between different powder deposition time intervals on thermal cycles, heat flux vectors and the resulting microstructures. Good agreement between the numerical and experimental results was found. The results obtained can be used for process optimisation.     

The using of LS-DYNA for the simulation of heat transfer in explosives

The using of FEM and especially LS-DYNA3D code for the simulation of a heat transfer during the heating of the explosive charge is discussed in this paper. The characterization of explosive material properties (density, thermal conductivity, specific heat, heat of decomposition, the decomposition kinetics) is described. LS-DYNA3D code is used for the fitting of the appropriate kinetic model and for the simulation of the heat transfer during the slow cookoff test. The results of simulations are compared to the experimental values for the SEMTEX 1A plastic bonded explosive.     

Imperfections generation in finite element models of welding

Welded components contain certain geometrical imperfections which may affect buckling behaviour of the final product. However, geometrical perfect models are usually used in the finite element method simulation. When a simple weld model is used, the mode of the end-distortion is predictable. Imperfections are created in the same shape as predicted. This paper presents a novel numerical approach on how to generate geometrical imperfections in finite element models. In this approach, as first, a large temperature gradient for the weld seam elements is prescribed. Then a linear steady-state thermal analysis is conducted and is followed by a structural analysis to determine the initial stress stiffness matrix for an eigenvalue analysis. The mode shapes of eigenvalue analysis are finally used to generate the imperfections. The results obtained in the course of this work allowed to calculate resultant welding distortion more accurate.     

Synthesis and properties of polyimides containing polybutadiene blocks

Polyimides containing polybutadiene blocks were prepared by copolycondensation of benzophenone-3,3′,4,4′-tetracarboxylic dianhydride, diphenylmethane-4,4′-diisocyanate and isocyanate-endcapped polybutadiene LBD-3000. ¹³C NMR CP-MAS and FTIR spectroscopies were used to determine the chemical structure of the copolymers. TGA showed that the thermal stability of the copolymers in inert atmosphere is almost independent of the polybutadiene content in the copolymer (as follows from the temperature of 10% and 20% weight loss). Stress–strain experiments showed that copolymers containing amounts of polybutadiene higher than 59 wt% exhibited elastomeric behaviour. © 1999 Society of Chemical Industry     

Application of the reaction kinetics and dispersion model to gas-solid reactors for removal of sulfur dioxide from flue gas

The conversions of a reactive, micro-grained limestone were studied in terms of exposure time and concentration of sulfur dioxide in the flue gas. The rates of the sulfation reaction were correlated as a function of the conversion of calcium oxide to sulfate and concentration of sulfur dioxide in the gas phase. In comparison with active sodium carbonate the sulfation of limestone particles proceeds at the rate which is substantially lower than the sulfation rate of soda particles.The empirical kinetic equation developed in this study is further applied in a two-phase dispersion model of simplified non-ideal flow behavior of the gas and solid in the reactor. The model can serve a rational basis for the conceptual design of a suitable contacting apparatus. Numerical solutions of the model equations outline possibilities and limitations of the dry lime process for the removal of sulfur dioxide from hot flue gas.     

Techniques of electrochemical determination of organic pollutants in water

Progressive polarographic and voltammetric techniques for analysis of trichlorobiphenyl thiourea and other compounds in water are discussed. A new type of electrochemical detector for HPLC is described.