Jelena S. Kiurski

Structural and textural properties of the NiOAl2O3 catalyst

Influence of nickel oxide loading (5; 10; 20 wt% Ni) and temperature of heat treatment (400, 700, 1100°C) on the structure, texture and reducibility of coprecipitated NiOAl2O3 catalyst was investigated. X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), low temperature nitrogen adsorption (LTNA) and hydrogen reduction confirmed significant changes in physico-chemical properties as the function of mentioned variables. The results showed that the interactions in coprecipitated NiOAl2O3 system are intensive even at 400°C. At 700°C the observed interactions in coprecipitated NiOAl2O3 system are surface area, reducibility and the coordination of Ni(II), while at 1100°C treatment intensive structural and textural changes were registered.

Microbial Deterioration Of Clay Roofing Tiles

The study illustrates both the biodeterioration and biomineralization actions of two fungus species (Aspergillus niger and Cladosporium sp.) and two organic acids (oxalic and acetic) and the action of the frost (frost dilatation studies in laboratory conditions) as the main factors of the process of ageing of clay roofing tiles. The nano-crystalline products, formed in this way, contribute to the abundant reactive surface area of the existing and new filled pores (due to the fungus hyphen penetration into the ceramic support) deepening the ageing processes of the clay roofing tiles. A relationship between the textural and microstructural characteristics of the studied systems and the formation of the specific crystal forms, developed after the actions of fungus, and oxalic/acetic acids was set up.

Electronic states of nickel(ii) in spinel-type structures

Abstract —The electronic spectra of Ni II as the promoter of a hydrodesulfurization catalyst (NiO-MoO 3 /γ-Al 2 O 3 ) has been studied. On the basis of the positions and intensities of the maxima in electronic d-d transitions the presence of an octahedral point group symmetry (O h ) of Ni II was established for the untreated sample and samples taken from the regenerated catalyst layers. In other cases, the distribution of d-d transition maxima indicated that in addition to the octahedral (O h ) a tetrahedral (T d ) coordination of Ni II was also present, suggesting the occurrence of a spinel-type structure. The experimental values obtained for the crystal field splitting parameter (10D q ) enabled calculation of the electronic state energies, as well as the values of parameters of partially populated d-orbitals of Ni II . On the basis of these data, the effective values of ionization potential H dd were calculated and a most probable MO scheme was proposed.

Arsenic distribution in water/sediment system of Sevojno.

Arsenic is a toxic and carcinogenic element. Its toxicity depends on its oxidation state and its concentration. The aim of this paper is to determine, for the first time, the concentration levels of arsenic in water and sediment during the spring/summer period of 2009 in Sevojno, a region in West Serbia with a long industrial tradition, as well as to determine the model of arsenic distribution in water/sediment system and the level of its compatibility with the existing theoretical model. Adsorption is a continual process in the environment. It plays a very important role in the transport and fate of pollutants, especially in sediment. The adsorption of arsenic was examined using the Freundlich adsorption isotherm.

Fuzzy prediction based on regression models: Evidence from the Belgrade Stock Exchange - prime market and graphic industry

In the conventional regression model, deviations between the observed values and the estimated values are supposed to be due to measurement errors. Here, taking a different perspective, these deviations are regarded as the fuzziness of the systems parameters. Thus, these deviations are reflected in a linear function with fuzzy parameters. Using linear programming algorithm, this fuzzy linear regression model might be very convenient and useful for finding a fuzzy structure in an evaluation system. In this paper, the details of the fuzzy linear regression concept and its applications in an uncertain environment are shown and discussed on data of the Belgrade Stock Exchange. In addition, the prediction of stock market prices is performed using fuzzy linear trend. Having in mind the characteristics of trading methods, fuzzy linear trend is used for prediction of stock market prices based on historical data, which are not precisely given within a trading day. Results of the research indicate the significance of fuzzy prediction based on regression models, i.e. fuzzy linear trend.

Occupational hazards in printing industry

This paper, through certain printing techniques, examines the types of occupational pollutants and the adverse impacts of the printing process. Also, it proposes the measures for better preservation and environmental protection. The paper analyzes the results of the quantitative identification of hazardous materials from various printing techniques: pad, screen, offset, flexographic, and digital. The study included the analysis of waste printing inks and purification of printing wastewater with adsorption methods. Besides that, the preliminary monitoring of ambient indoor air quality was performed. The multiple regression analysis was applied on the obtained experimental results, in order to determine the mutual correlation between the ozone and the total volatile organic compounds and microclimate parameters. It was observed that a quantitative correlation exists between the investigated occupational hazards, which also indicate the strength of the agreement. The obtained results could be useful to evaluate the tendency of hazardous air pollutants in printing industries worldwide.

Fuzzy uncertainty analysis in the investment processes

The analyses of the investment processes, especially the possibility of monitoring and forecasting the intense return fluctuations, demands usage of an appropriate framework, which adequately evaluates the dynamic nature of those processes. In the recessive business conditions, volatility and extreme stock market movements presents a challenge while evaluation of the investment processes. Thus, the stock market prices volatility and the possibility of stock market forecasting in an uncertain environment are in the focus of the research. Fuzzy sets allow usage of approximated values of the ambiguous data, that is, the intraday stock market prices data. The sample comprises stocks of Alfa plam a.d. Vranje (ALFA), Komercijalna banka a.d. Beograd (KMBN) and Metalac a.d. Gornji Milanovac (MTLC), that are traded at the regulated market of the Belgrade Stock Exchange. The main goal of the research is to present an overview and performance test of the fuzzy sets as a part of soft computing (SC) technology in the investment processes. The research results indicate the necessity of the fuzzy sets application in the forecasting of stock market prices, i.e. its approximate values.

Application of neural networks in investments: A case of BELEX15 stock index

The time series represent a line of observations of unintentional variable in different time periods. The aim of the time series is, on the basis of those observations, to forecast the values of the variable. Further reactions should be predicted on the basis of the data from the past. The research covers the sample representing the Serbian (BELEX15) stock index. The aim of this study is the survey of the algorithm for predicting the reaction of the problem of this type by using the neural networks in function of prediction of the daily stock index values in the emerging market of the Republic of Serbia. The proposal of the algorithm is implemented by software and the results are significant both to academics and professionals in the subject area, especially having in mind the possibility of prediction in investments.

Metal concentration and particle size distribution of stream and river water polluted from copper rolling mill industry

Concentrations of heavy metals, pH, and particle size distribution parameters were measured in Dragica stream and Djetinja River water receiving wastewaters from copper rolling mill industry, Sevojno. The concentrations of copper, zinc, lead, and mercury were determined for water samples collected in summer 2009. It was found that Copper Rolling Mill Sevojno was the significant source of water pollution with copper and zinc. Considering that copper rolling mill industry, one of the larger emitters of sulfur dioxide, pollutes the area, the water pH was surprisingly alkaline. The particle size analysis results showed that particles from oil-in-water emulsion evidently got into stream water in spite of the purification devices used. In order to assess the possible relations between the measured parameters, a correlation analysis was performed. The correlation analysis showed a significant positive correlation between the total metal concentrations of copper and zinc, as well as between particle size distribution parameters and the concentration of lead and copper.

Spinel-type structure of Co in conditions of HDS catalyst aging

Abstract The structural investigation of CoO–MoO 3 / γ -Al 2 O 3 HDS catalystassumed to accelerate aging in laboratory conditions followed by the DRS method pointed out the surface spinel formation The amount of spinel structure formed increased with increasing temperature and decreased with the treatment atmosphere in the order: nitrogen>air>steam On the basis of the experimental data of electronic d–d transitions of Co (II) ion in a catalyst treated in nitrogen atmosphere the parameter of the crystal-field splitting 10 D q and the energies of the electronic state of Co (II) in a spinel-type structure were calculated The most probable scheme of the molecular orbital has been proposed.