Most researchers have explored noise reduction effects based on the transfer matrix method and the boundary element method. However, maximum noise reduction of a plenum within a constrained space, which frequently occurs in engineering problems, has been neglected. Therefore, the optimum design of multi-chamber plenums becomes essential. In this paper, two kinds of multi-chamber plenums (Case I: a two-chamber plenum that is partitioned with a centre-opening baffle; Case II: a three-chamber plenum that is partitioned with two centre-opening baffles) within a fixed space are assessed. In order to speed up the assessment of optimal plenums hybridized with multiple partitioned baffles, a simplified objective function (OBJ) is established by linking the boundary element model (BEM, developed using SYSNOISE) with a polynomial neural network fit with a series of real data – input design data (baffle dimensions) and output data approximated by BEM data in advance. To assess optimal plenums, a genetic algorithm (GA) is applied. The results reveal that the maximum value of the transmission loss (TL) can be improved at the desired frequencies. Consequently, the algorithm proposed in this study can provide an efficient way to develop optimal multi-chamber plenums for industry.

The aim of this work was to compare nitrogen dioxide atmspheric pollution in some parts of Cracow and to indicate the area in which ambient air concentration of N02 may be the highest. The measurements of 24- hour N02 concentrarion were made by spectrophotometric method with passive sampling in 20 sites in the period of 2 years. The results were analysed by statistical methods, such as: analysis of variance and correlation. The 24-hour NO, concentration has significant spatial variation in the area of Cracow. The highest values were measured in the street canyons, the lowest in residential areas. The highest values of N02 concentration were observed during heating season. The results of passive method are comparable with the results of authomatic method and because of this both methods may be use together in monitoring networks.

Due to the occurrence of zinc and lead ore deposits in dolomite rocks, the sphalerite concentrates obtained from these ores contain an admixture of dolomite. In practice, a substantial amount of magnesium included in zinc ores passes to the last production stage, i.e. zinc electrolysis. The magnesium present in electrolyte impairs electrical conductance and appears in the technical and economical indexes. This paper deals the attempts to remove magnesium removal from initial sphalerite concentrates by means of chemical flotation using spent electrolyte derived from zinc electrolysis. The authors attempt to substantiate the existing relationships, as well as to derermine the optimum conditions for the procedure suggested. The leaching efficiency of magnesium amounted to about 80%, and is dependent upon the stage of the leaching. Losses of zinc were below 2%, and the magnesium concentration in solution amounted to about 20%. These solution can produce magnesium and zinc, which will be presented in the following paper.

Our study involved the first-ever evaluation of the performance of anther culture and wheat × maize hybridization techniques in producing haploids or doubled haploids as a result of spontaneous doubling of the chromosome number during androgenesis in plants from 30 wheat genotypes including ancient, local and modern types. The results indicated that the best induction rates of androgenic structures and haploid embryos for the hexaploid and tetraploid wheat genotypes were obtained with anther culture and wheat × maize hybridization, respectively. Whereas only one regenerated plant from 15 genotypes of tetraploid wheat was obtained, 13 plants were regenerated from 15 genotypes of hexaploid wheat. Moreover, haploid embryos obtained in wheat × maize hybridization 60 and 100% green plants regenerated in relation to the number of the cultured haploid embryos. Genotypes with high induction capacity to produce androgenic structure or haploid embryos did not have desired haploid plantlets regeneration capacity and vice-versa. However, with both methods, hexaploid wheat genotypes had a considerable ability to produce green plants. Doubled haploid plants were obtained from ancient and local wheat genotypes by both methods, but not from modern wheat. Those genotypes can be used as parents in future wheat breeding programs and new varieties may be obtained by selecting pure lines in wheat populations

The employment of green synthesized nanomaterials for water pollution prevention is increasing nowadays. Herein, Mn-doped ZnO nanoparticles were synthesized using Peganum Harmala seed extract and subsequently used for crystal violet (CV) dye removal from aqueous solutions. The first part of the study describes the preparation of the adsorbent (Mn-ZnO NPs) using a simple coprecipitation method. The surface properties of the material were characterized by Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The second part investigates the adsorption of CV dye onto the surface of the prepared Mn-ZnO NPs. Additionally, the isotherm,kinetics, and thermodynamics of the adsorption process were studied in detail. Batch adsorption analysis was carried out by evaluating different parameters, such as the amount of the adsorbent (0.01g to 0.04 g), CV concentration (20 to 80 mg/L), adsorption time (30 to 120 min), and temperature (35 to 65 ⁰C). The maximum CV dye adsorption capacity of the Mn-ZnO NPs was 45.60 mg/g. The thermodynamic study revealed the spontaneous, exothermic, and feasible nature of the adsorption process, primarily driven by physical forces. Kinetic and isotherm analyses indicated that the adsorption of the dye best fit the Freundlich isotherm and pseudo-second-order models, respectively. Mn-doped ZnO is considered an effective adsorbent for CV, benefiting from its rapid and easy preparation, non-toxic nature, and 94 % adsorption efficiency. The material holds potential for future applications in the removal of organic dyes from wastewater.