The paper reports the consequences of lanthanum modifications of barium bismuth niobiate (BaBi2Nb2O9) ceramics. The discussed materials were prepared by solid state synthesis and a one-step sintering process. The investigations are focused on dielectric aspects of the modification. The presented results reveal that the trivalent lanthanum ions incorporate twovalent barium ions, which is connected with the creation of A-site cationic vacancies as well as oxygen vacancies. Such a scenario results in significant decreasing in grain boundaries resistivity. The activation energy of grain boundaries conductivity is significantly reduced in the case of lanthanum admixture.

One major problem in the design of ultrasonic transducers results from a huge impedance mismatch between piezoelectric ceramics and the loading medium (e.g. gaseous, liquid, and biological media). Solving this problem requires the use of a matching layer (or layers). Optimal selection of materials functioning as matching layers for piezoelectric transducers used in transmitting and receiving ultrasound waves strictly depends on the type of the medium receiving the ultrasound energy. Several methods allow optimal selection of materials used as matching layers. When using a single matching layer, its impedance can be calculated on the basis of the Chebyshev, DeSilets or Souquet criteria. In the general case, the typically applied methods use an analogy to a transmission line in order to calculate the transmission coefficient T. This paper presents an extension of transmission coefficient calculations with additional regard to the attenuation coefficients of particular layers. The transmission coefficient T is optimised on the basis of a genetic algorithm method. The obtained results indicate a significant divergence between the classical calculation methods and the genetic algorithm method.

An efficiency of the nonsingular meshless method (MLM) was analyzed in an acoustic indoor problem. The solution was assumed in the form of the series of radial bases functions (RBFs). Three representative kinds of RBF were chosen: the Hardy’s multiquadratic, inverse multiquadratic, Duchon’s functions. The room acoustic field with uniform, impedance walls was considered. To achieve the goal, relationships among physical parameters of the problem and parameters of the approximate solution were first found. Physical parameters constitute the sound absorption coefficient of the boundary and the frequency of acoustic vibrations. In turn, parameters of the solution are the kind of RBFs, the number of elements in the series of the solution and the number and distribution of influence points. Next, it was shown that the approximate acoustic field can be calculated using MLM with a priori error assumed. All approximate results, averaged over representative rectangular section of the room, were calculated and then compared to the corresponding accurate results. This way, it was proved that the MLM, based on RBFs, is efficient method in description of acoustic boundary problems with impedance boundary conditions and in all acoustic frequencies.

Two optimization aspects of the meshless method (MLM) based on nonsingular radial basis functions (RBFs) are considered in an acoustic indoor problem. The former is based on the minimization of the mean value of the relative error of the solution in the domain. The letter is based on the minimization of the relative error of the solution at the selected points in the domain. In both cases the optimization leads to the finding relations between physical parameters and the approximate solution parameters. The room acoustic field with uniform, impedance walls is considered.

As results, the most effective Hardy’s Radial Basis Function (H-RBF) is pointed out and the number of elements in the series solution as a function of frequency is indicated. Next, for H-RBF and fixed n, distributions of appropriate acoustic fields in the domain are compared. It is shown that both aspects of optimization improve the description of the acoustic field in the domain in a strictly defined sense.

The evaluation of complex radiation impedance for a square piston source on an infinite circularcylindrical baffle is associated to the Greenspon-Sherman formulation for which novel evaluation methods are proposed. Unlike existing methods results are produced in a very wide range of frequencies and source semi-angles with controllable precision. For this reason closed-form expressions are used to describe the truncation errors of all integrals and infinite sums involved. Impedance values of increased accuracy are also provided in tabulated form for engineering use and a new radiation mass-load model is derived for low-frequencies.

Scattering of sound waves in two stepped cylindrical duct which walls are coated with different acoustically absorbent materials is investigated by using Wiener-Hopf technique directly and by determining scattering matrices. First, by using Fourier transform technique we obtain a couple of modified Wiener-Hopf equations whose solutions involve four sets of infinitely many unknown expansion coefficients providing systems of linear algebraic equations. Then we determine scattering matrices of the problem and we state the total transmitted field by using generalized scattering matrix method. Numerical results are compared for different parameters.

The corrosion inhibition behaviour of 1-Ethyl-3-methylimidazolium-methanesulphonate (EMIM[MS]) and 1-Ethyl-3-methylimidazolium acetate (EMIM[Ac]) on API 5L X-52 carbon steel in 2 M HCl was investigated using weight loss, potentiodynamic polarization and electrochemical impedance methods. The corrosion rates of carbon steel decreased in the presence of these ionic liquids. The inhibition efficiencies of the compounds increased with concentration and showed a marginal decrease with a 10°C increase in temperature. Polarization studies showed the compounds to be mixed type inhibitors with stronger anodic character. The adsorption mechanism of both compounds on the metal surface was via physical adsorption and the process obeyed the El-Awardy kinetic-thermodynamic model. The associated activation energy of corrosion and other thermodynamic parameters were calculated to elaborate on the thermodynamics and mechanism of the corrosion inhibition process. EMIM[MS] was found to inhibit the corrosion of carbon steel better than EMIM[Ac] and is attributed to the presence of the highly electronegative sulphur atom in its structure and its larger molecular size.

Nifedipine, a pyridine derivative was investigated as corrosion inhibitor for API 5L X-52 steel in 2 M HCl solution by potentiodynamic polarization, electrochemical impedance spectroscopy and quantum chemical calculations. Statistical tools were used to compare results of the experimental methods. The results showed that nifedipine is capable of inhibiting the corrosion of API 5L X-52 steel in 2 M HCl solution. Potentiodynamic polarization results reveal that nifedipine functions as a mixed-type inhibitor and presents an inhibition efficiency of about 78% at 500 ppm. Impedance data reveal an increasing charge transfer resistance with increasing inhibitor concentration and also shows comparable inhibition efficiency of about 89-94% at 500 ppm. Thermodynamic parameters imply that nifedipine is adsorbed on the steel surface by a physiochemical process and obeys Langmuir adsorption isotherm. The calculated molecular properties namely the highest occupied molecular orbital energy, lowest unoccupied molecular orbital energy, chemical hardness, energy gap, dipole moment, electronegativity and global nucleophilicity index all show a positive relationship to the observed corrosion inhibition efficiency.

The hierarchical structure of InSe<β-CD<FeSO₄>> composition with 4-fold grade expansion was synthesized with the intercalation-deintercalation technique. Electrical properties of the structure obtained were examined using impedance and thermostimulated current spectroscopy methods. Influence of temperature, static magnetic field and illumination on electrical properties of the synthesized compound was investigated. Changes in the impurity spectrum of the expanded hierarchical structure were analyzed and extraordinary magneto- and photoimpedance behavior of InSe<β-CD<FeSO₄>> at room temperature was explained.

Al2Cu phase has been obtained by melting pure metals in the electric arc furnace. It has been found that the intermetallic phase undergoes selective corrosion in the H3PO4 aqueous solutions. Aluminium is dissolved, the surface becomes porous and enriched with copper. The corrosion rate equals to 371 ± 17 g·m–2·day–1 (aerated solution) and 284 ± 9 g·m–2·day–1 (deaerated solution). The surface of Al2Cu phase after selective corrosion was characterised by using electrochemical impedance spectroscopy. It was found that the surface area of the specimens increases with temperature due to higher corrosion rate and is between 2137 and 3896 cm2.

An emerging ultrasonic technology aims to control high-pressure industrial processes that use liquids at pressures up to 800 MPa. To control these processes it is necessary to know precisely physicochemical properties of the processed liquid (e.g., Camelina sativa oil) in the high-pressure range. In recent years, Camelina sativa oil gained a significant interest in food and biofuel industries. Unfortunately, only a very few data characterizing the high-pressure behavior of Camelina sativa oil is available. The aim of this paper is to investigate high pressure physicochemical properties of liquids on the example of Camelina sativa oil, using efficient ultrasonic techniques, i.e., speed of sound measurements supported by parallel measurements of density. It is worth noting that conventional low-pressure methods of measuring physicochemical properties of liquids fail at high pressures. The time of flight (TOF) between the two selected ultrasonic impulses was evaluated with a cross-correlation method. TOF measurements enabled for determination of the speed of sound with very high precision (of the order of picoseconds). Ultrasonic velocity and density measurements were performed for pressures 0.1–660 MPa, and temperatures 3–30XC. Isotherms of acoustic impedance Za, surface tension σ and thermal conductivity k were subsequently evaluated. These physicochemical parameters of Camelina sativa oil are mainly influenced by changes in the pressure p, i.e., they increase about two times when the pressure increases from atmospheric pressure (0.1 MPa) to 660 MPa at 30XC. The results obtained in this study are novel and can be applied in food, and chemical industries.