Application of integral equations to solving inverse problems of stationary electromagnetic fields

A method of solving inverse problems of stationary electromagnetic fields is described. It can be applied to problems in non-homogeneous, linear and isotropic environments. The method is based on application of integral equations of the first kind which require regularization because they are ill-posed. Numerical calculations of some selected problems confirm the effectiveness of the proposed method.     

On some parameters of interaction of glass neodymium laser beam with metal surfaces having different roughness

Samples of 45 steel and MO60 brass with the surface roughness ranging from 0.5 ÷ 8 μm were irradiated with strong pulses of a glass neodymium laser working in ordinary generation régime (λ = 1.06 μm, E = 6 J, τ = 2 ms). The parameter of roughness h? was determined by means of an optical reflexometric method. The dependences of the chosen parameters of the interaction, i.e. the amount of the mass Δ m removed from the crater, the depth H and the mean radius r_o of deep cavities being formed were examined as a function of h?.     

The influence of adsorbent texture and adsorbate type on analytical functions describing the heterogeneity of active carbons surfaces

Analytical functions describing the heterogeneity of active carbons have been studied in relation to adsorbate type and adsorbent texture. It has been found that the maximum in the distribution functions shifts to higher energies with an increase in adsorbent microporosity. The position of the maximum on the curve determining active carbon heterogeneity is closely correlated with the value of the B parameter in the Dubinin-Astakhov equation. It has been shown that the shape and magnitude of the analytical functions studied depend on the type of adsorbate molecules bonded on the adsorbent surface.     

Effect of water content on the hardness of Edam cheese

It is proposed that the physical properties of cheese, in particular hardness, depend on moisture content. A statistical analysis of the experimental data in support of the proposal has been carried out. Empirical equations describing the changes in physical properties with moisture content in Edam cheese after pressing, during ripening, and as marketed, have been developed. A transformed function is proposed that makes possible the control of Edam cheese hardness by regulation of the dehydration level during the pressing operation.     

Electrochemical determination of pollutants in sea water: Toxic substances and nutrients

Coastal marine waters have a wide variety of important human uses and therefore must be protected against contamination. The main sources of their pollution (by toxic substances and nutrients) are the discharge of municipal sewage and runoff from agricultural areas. Excessive nutrient enrichment in the form of inorganic nitrogen (NH₄⁺, NO₂^?, NO₃^?) may be directly estimated by the use of ion selective electrodes (ISE), whereas the inorganic phosphorus can only be estimated indirectly. The total content of N, P and heavy metals may be estimated after decomposition of organic substances, using the ISE method in the case of P and N determination and the differential pulse anodic stripping voltammetry (DPASV) method for determining the heavy metals.     

Synthesis of aminoarylsulphonanilides derived from o-chlorotoluene

Fifteen new arylsulphonanilide amines containing at least one o-chlorotoluene residue in a molecule have been synthesized. Their compositions have been confirmed by elementary analysis and infrared spectrophotometry. These amines can be used to synthesize acid and reactive dyes.     

Kationische Polymerisation von Styrol im Durchfluß-System. II. Einfluß der parameter der styrololigomerisation mit schwefelsäure bei völliger umsetzung des monomeren auf das molekulargewicht der oligomeren

A continuous stirred tank reactor was applied to conduct the cationic oligomerization of styrene in benzene solution in the presence of concentrated sulphuric acid. The influence of the monomer concentration, temperature and holding time on the average molecular weight of the oligomers in case of complete monomer conversion was investigated by means of a statistical analysis. A minimax-type function resulted. There was found occurence of some maximum values of the molecular weight as a function of the monomer concentration as well as occurence of some minimum values of the molecular weight as a temperature function and also as a function of the holding time. The saddle point coordinates were determinated as follows: 1,65 mol/1; 32,5°C; 2,54 min, whereas the molecular weight in this point was 293,4 g/mol in a 95% confidence interval 283,5 to 304,0 g/mol. An undoubtful effect of the interaction of temperature and of holding time with increase of the molecular weight as well as the dominant role of the monomer concentration with decreasing molecular weight of the oligomer were found to be the characteristic features of the investigated reaction.     

Surface modification of PET membrane by ion implantation

Semicrystalline poly(ethylene terephtalate) (PET) foils were irradiated with N⁵⁺, O⁷⁺ and C³⁺ ions. Ions beams of 50 keV N⁵⁺, 70 keV O⁷⁺ and 30 keV C³⁺ were produced from the ECR ion source. The induced effects and wettability of ion-implanted membranes were investigated by means of the Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and by the contact-angle methods. FTIR measurements of the virgin and irradiated samples show the scission processes of main chains at the ethylene glycol residue. Various degradation processes known from photochemical degradation were also observed. The AFM observation revealed that the surface topography changes after irradiation. The contact-angle measurements showed that the PET membranes became significantly more hydrophilic after the ion irradiation.