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The paper shows the possibilities of increasing the hydrophobicity of the paper surface by applying layers of hydrophobic material to the surface. Various application techniques and the following substances were tested: stearic acid, shellac and zinc-hydroxide. Hydrophobicity was tested using the modified Cobb method, measuring the contact angle and drop retention time. The presence of hydrophobizing agents was confirmed by FTIR spectroscopy. It was found that the methods of applying the hydrophobizing agent, used in this work, give much better results with stearic acid, compared to shellac. This manuscript presents novel possibilities of increasing paper surface hydrophobicity by applying layers of hydrophobic material to the surface. Various layer application techniques were examined, as well as substances including: stearic acid, shellac and zinc-hydroxide. Hydrophobicity was tested using the modified Cobb method, measuring the contact angle and drop retention time. The presence of hydrophobizing agents was confirmed by FTIR spectroscopy. Based on the results achieved, it can be concluded that the methods of applying the hydrophobizing agent, used in this work, give much better results with stearic acid, compared to shellac.

Polymer resins based on acrylates obtained from Bis-GMA (Bisphenol A glycide methacrylate), which is suitable for photopolymerization, are used in dentistry for various purposes due to the ease of application and the possibility to influence their properties by adding reinforcements of different shapes, crystal structure and chemical compositions. Reinforcement in the form of particles based on MgAlLDH (layered double hydroxide) deposited on silica obtained from rice husks on two substrates. A metal base and glass were used. The adhesive properties are important in order to see the possibility of using these materials in applications. In order to measure the adhesive properties of the material, the composite microhardness measurement method is used by applying different loads in order to evaluate the adhesion parameter that shows the effect of the coating on the substrate. It was compared to how a pure photopolymerizing acrylate matrix bonds with a chromium-based dental alloy substrate that is used in the production of different parts of dentures by bonding to a glass substrate. Then, it was compared how composite materials are bonded to both substrates. Adhesion was monitored through the change in wetting angle between the composites, and the results were compared with the results of microindentation. It was shown that the addition of composite particles increases the adhesive properties of the composite compared to the pure matrix and that better adhesion is achieved between the composite and the metal substrate than between the composite and the glass substrate.

The review of the work "Working from Home - Economic, Legal and Socio-Psychological Aspects of Working from Home" lists the features of the culture and history of work that may be considered a map of information capitalism, although work from home can be traced back to not so modern or recent epochs. However, what is in the focus of this "research reformation" of the team of authors are definitely new models of (self)employment that, as it can be clearly seen in the authors' statements, arise or have arisen as independent paradigms in relation to the COVID-19 pandemic. On the other hand, the pandemic encouraged the conduct of a number of compatible studies whose socio-psychological comparisons are used by the authors as a basis to justify their originality. The monograph clearly emphasizes the demarcation claims of working from home, as well as other "horizon of information existence", or a new entrepreneurial culture. Therefore, apart from the ever more present work culture that is reflected in working from home in informatic capitalism, our task is also to show the results of indicating the possibility of legal, economic and socio-psychological development of freelancers as an entrepreneurial layer in the Serbian society.

When different observers match the same color, using the same matching stimuli, it is found that there are slight differences in the amounts that they require to make up a match. The interpretation of color differences plays an important role in some cases, for example in color evaluation during print approval, when the designer has high requirements regarding the accuracy of color reproduction, for medical purposes, in the automotive or other industries. There are several tests for determining who is the best candidate for evaluating colors. One of the most convenient tests is the Farnsworth-Munsell 100 Hue Test. The main disadvantage of this and similar tests is that one can't straightforwardly connect perceptual interpretation of color differences with objective results done with instrumental measurement of color differences. The paper proposed a way to express in ΔE* units the results of testing the subject's sensitivity to color differences, and in that way to determine as precisely as possible the difference in color that an individual subject can perceive in some part of the colored space. By calculating the average value of ΔE* of the respondents for certain parts of the color space, a conclusion can be drawn about the general sensitivity of the respondents to differences in colors. [ABSTRACT FROM AUTHOR]

Introduction: Bronchiolitis is an acute viral disease of lower respitatory pathways in children under 2 years of age. It is manifested by coughing, whistling and refusing food intake. The most common cause of bronchiolitis is a respiratory syncytial virus. Vitamin D is a steroid hormone which is synthesized in the skin after sun exposure or food intake. With discovery of Vitamin D receptors and hydroxylated enzymes in immune cells, a potential role for Vitamin D in maintaining immune homeostasis was seen. It has been established that Vitamin D induces a change of the antimicrobial polypeptide, cathelicidin, which has both antibacterial and antiviral roles. Objective: Determine whether the serum Vitamin D levels in acute viral bronchiolitis patients from Central Kosovo is lowered. Methods: This prospective study included 34 children aged up to 2 years, that have been diagnosed with the heavy form of acute viral bronchiolitis. Blood was drawn from all subjects to analyze serum Vitamin D levels. Results:Average levels of Vitamin D, measured in all subjects, was 35.5 ng/ml. After Vitamin D levels stratification, 62% of the subjects had normal levels of serum Vitamin D, while 38% of the subjects had lower levels of serum Vitamin D. 15% of children had lower levels than 20 ng/ml. With children of ages up to 12 months there was a statistical significance of negative direction between Vitamin D serum levels and body height (r=-0.683, p=0.010) and between Vitamin D serum levels and body weight (r=-0.725, p=0.005). With children of ages up to 24 months there was only a statistical significance of negative direction between Vitamin D levels and body height (r=-0.540, p=0.011). Conclusion: Our research confirmed that children with acute viral bronchiolitis have a significant deficiency of Vitamin D, although it's a required addition to nutrition for children under the age of 2 years.

The morphologies of copper dendritic forms obtained in both potentiostatic and galvanostatic regimes of electrolysis with various amounts of the electricity were analyzed by the scanning electron microscopy (SEM) technique. Irrespective of amount of passed electricity, 3D (three dimensional) pine-like dendrites with sharp tips were formed in the potentiostatic regime of electrolysis. On the other hand, the amount of passed electricity had a strong effect on the shape of the 3D pine-like dendrites formed in the galvanostatic regime of electrolysis. Dendrites with sharp tips were formed with smaller amount of passed electricity, while dendrites with globular tips were formed with larger amounts. The change in the shape of the galvanostatically synthesized 3D pine-like dendrites was explained by comparison with copper deposits obtained potentiostatically at overpotentials that corresponded to the final overpotentials during galvanostatic regime of electrolysis for the analyzed amounts of electricity. Based on the similarity of the obtained morphologies at the macro level, it was concluded that the overpotential plays a crucial role in the formation of the electrolytically synthesized dendrites and that the controlled conditions of electrolysis could represent a suitable way for a synthesis of spherical Cu particles by electrolysis. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172046: Electrochemical synthesis and characterization of nanostructured functional materials for application in new technologies]

Starting from the problems of bias and validation in combining different research methods and methodologies, the paper discusses the advantages and shortcomings of triangulation. The triangulation concept which involves the use of more than one method to obtain records from more than one source is critically analyzed, and particularly the justification of defining the goal of triangulation as a process that is used to better understand social phenomena by looking at them from more than one perspective. The author points out the importance of the awareness that triangulation does not necessarily lead to an attempt to support the findings, taking into account the four concepts: triangulation as validation check, continuous triangulation, triangulation as a search for the completeness of information/image and triangulation as epistemological dialogue. To solve the problem of the corresponding metaphor and analogy with the original meaning of triangulation, the author suggests an anamorphic paradigm: different methods are combined as a product of different theoretical traditions, and their combination can add depth and scope, but not accuracy; a clearer picture (and this is only possible to achieve, not accuracy) is obtained by choosing the appropriate perspective, angle, and point of view.

A novel double layered hybrid materials, consisting of low density polyethylene (LDPE) base layer and polycaprolactone (PCL) top layer containing surface modified nanocellulose (NC) based nanocomposites in 0.5 and 2 % loadings, were studied in order to design multipurpose packaging material. NC was covalently modified with maleic anhydride (MA) to obtain NCMA, and upon co-precipitation of copper (II) oxide (CuO) on NC and NCMA surface, NC-CuO and NCMA-CuO nanocomposite materials were produced. Two drying methods, conventional and lyophilization, were applied to investigate process influences on the properties of obtained hybrid material. Oxygen transmission rate and antimicrobial activity were determined for all produced hybrid materials. PE-PCL-NCMA-CuO-L2 exhibited the highest antifungal properties, indicating contribution of MA residual group and drying conditions (liophylisation) to achievement of 97 % reduction in cell viability of C. albicans. The sample with 2 % of NCMA-CuO, PE-PCL-NCMA-CuO2, demonstrated to be the most promising material regarding improvement in antibacterial and antifugal activity, as well as 16 % lower value of the oxygen transmission rate in comparison to pure LDPE. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III45019]

Naturally flows have been the scope of the scientific research for centuries, Rayleigh-Benard convection being one of the leading. Many researchers have considered the flow patterns, boundary conditions, various cavities, nanofluids, theoretically, numerically, and experimentally. The flow was investigated in atmosphere and in nanofluids, in air, water, molten metals, non-Newtonian fluids. Almost all research focuses on 2-D or 3-D analysis of flow in laterally unlimited enclosures, as parallel plates or coaxial cylinders. In technical practice, only limited enclosures exist. This paper presents numerical and real experimental results for the test chamber with ratio 4×2×1 in x-, y-, and zdirection, respectfully. The measurements were taken at fifteen different positions on the faces of the tank. Probes used are PT100 elements. As the chamber is limited in all directions, the results have shown strong influence of the lateral walls. The results are compared with the those obtained by IR camera. Various fluids were tested, and results for motor oil will be presented. [ABSTRACT FROM AUTHOR]

The processes of lead and zinc electrodeposition from the very dilute electrolytes were compared by the analysis of polarization characteristics and by the scanning electron microscopic (SEM) analysis of the morphology of the deposits obtained in the galvanostatic regime of electrolysis. The exchange current densities for lead and zinc were estimated by comparison of experimentally obtained polarization curves with the simulated ones obtained for the different the exchange current density to the limiting diffusion current density ratios. Using this way for the estimation of the exchange current density, it is shown that the exchange current density for Pb was more than 1300 times higher than the one for Zn. In this way, it is confirmed that the Pb electrodeposition processes are considerably faster than the Zn electrodeposition processes. The difference in the rate of electrochemical processes was confirmed by a comparison of morphologies of lead and zinc deposits obtained at current densities which corresponded to 0.25 and 0.50 values of the limiting diffusion current densities. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172046]

This paper presents an analysis of a biomass-fired steam boiler with capacity of 14 MW which produces saturated steam at pressure of 14 bar using agriculture residue straw as fuel. The boiler operates with flue gas recirculation rate of 20%, a common technique to improve the efficiency of the combustion process and reduce emission. Data from the PLS sensors were collected to evaluate the boiler's performance. Thermal calculations were performed to analyze the heat transfer rate, heat loss, and combustion efficiency of the boiler. Three different cases were considered: flue gas recirculation after the bag filters, recirculation after the flue gas channel exit, and without the recirculation. Parallel, the emission of NOx for all scenarios was discussed. The analysis of the results shows that for both cases flue gas recirculation yields almost the same efficiency. However, the efficiency for lower flue gas recirculation is increased, and without flue gas recirculation was the highest according to both the model and calculations. This suggests that while flue gas recirculation can be an effective way to improve combustion efficiency and reduce emissions, it may not always be the most optimal solution. The findings of this study provide valuable insights into the biomass-fired steam boilers performance and the impact of flue gas recirculation on their efficiency and NOx emission. These insights can be useful for optimizing the design and operation of similar biomass-fired steam boilers and for promoting the use of renewable energy sources in industrial processes. [ABSTRACT FROM AUTHOR]

This study aimed to determine part-time teachers’ attitudes (based on a sample of respondents from the Republic of Serbia) (N=727) about school climate and job satisfaction; it also aimed to examine the nature, level, and intensity of the connection between these two complex variables. To examine such attitudes, we used several questionnaires on school climate and job satisfaction extracted from the Teaching and Learning International Survey (TALIS), 2013. Based on the instrument we utilised, the school climate could be categorised and studied as a two-component dimension reflecting two aspects of part-time teachers’ school life: general school issues, and issues related to students’ needs and well-being. We concluded that there is a significant correlation between part-time teachers’ school climate and job satisfaction. School climate explains 27% of the job satisfaction variance, indicating the importance of the observed regression relationship. [ABSTRACT FROM AUTHOR]

The simulated shapes of the polarization curves were correlated with the type of metal electrodeposition process control in a function of the exchange current density to the limiting diffusion current density (j0/jL) ratios. Diagnostic criteria based on the j0/jL ratios were established. For j0/jL> 100, the system is under the ohmic control. In the range 1 < j0/jL ≤ 100 there is the mixed ohmic-diffusion control. The pure diffusion control appears in the range 0.1 < j0/jL £ 1. For j0/jL £ 0.1, the system is activation controlled at the low overpotentials. The proposed diagnostic criteria were verified by comparison of the simulated curves with experimentally recorded ones and by morphological analysis of deposits obtained in the different types of metal electrodeposition process control. [Projekat Ministarstva nauke Republike Srbije, br. 172046: Electrochemical synthesis and characterization of nanostructured functional materials for application in new technologies]

In order to improve the mechanical properties of paper, 1, 3 and 5 wt.% of sepiolite were dispersed in a poly(vinyl butyral) (PVB) matrix and coated onto the surface of schrenz (110 g m-2). Deagglomerated sepiolite nanofibers in PVB matrix on paper surface were observed by scanning electronic microscopy. The glass transition temperature of schrenz with PVB/sepiolite coatings was not changed with increasing content of sepiolite. Two different methods were used to evaluate the mechanical properties of the paper sample reinforced with PVB/sepiolite nanocomposites: tensile testing and nanoindentation. The values of breaking force and tensile energy absorption of the reinforced paper samples obtained by tensile testing were increased by up 10 %. The values of the reduced elastic modulus and hardness obtained by nanoindentation were increased by up to 78 %. The best improvement of the mechanical properties was shown by the paper sample coated with PVB/3 wt.% sepiolite nanocomposite. [Projekat Ministarstva nauke Republike Srbije, br. III 45019]

Border municipalities in eastern Serbia have peripheral position in relation to the central state territory: geographical distance from the administrative, political, economic and cultural center shaping their overall social development, which is generally far behind the devel­opment of other parts of Serbia. At various stages of transition, starting from the nineties to the present, the border municipalities were, it seems, more exposed to the negative effects of the neoliberal development strategy: there was a change of ownership of industry, as well as a deindustrialization, which led to significant reduction of the workforce. The devastation of the economies in these areas has intensified negative demographic processes in the border municipalities of Eastern Serbia with the onset of the economic crisis in the eighties and the subsequent processes there caused: (a) depopulation (population between census periods from 1991 to 2011 fell by more than 20% of the territory of Bor district), (b) reduction in the birth rate, which for decades was showing negative trends (eg. natural growth rate in the Negotin krajina, according to the Census of 2011, amounts to -6.7 % annually) (v) migration of the young, working population (Census 2011) shows that nearly one-quarter of the economically active population of the Bor district 'work abroad', ie. employment is found in western European countries, they educate their own children there and, apparently, do not intend to return to the place of birth. The devastation of the economy leads to a legitimate social devastation and collapse of culture (Mitrović, 2009) and education. The main parameter to be monitored in the new neoliberal strategies of development is economic growth, which points to the direction of changes in macroeconomic processes, but not to the improvement of the quality of life of people who participate in these processes. The achieved rate of economic growth does not automatically provide sustainable development of all areas of society, especially not their balanced development. Therefore, different development policies, such as education (and / or educational) policy, in addition to economic parameters must take into account other parameters relevant to the allocation of decision-making. The question of the network of schools, we believe, is not primarily a question of the commercial viability of their establishment and maintenance, but the crucial question of survival of the impoverished and emptied border municipalities. According to data from the School Administration of Zaječar, during the school year 2011/12, shows that (a) complete (eight-year schools) do not exist in all observed municipalities, which raises the issue of equal opportunities of education (access to resources - time and financial) and (b) offered educational profiles of secondary schools were reduced compared to the educational profiles of the larger and more developed municipal centers in Serbia, which leads to inequality of high school students in the choice of a profession: the same were referred for decision-making in the framework of the existing modest offer and not in accordance with their own interests and predispositions. The authors believe that the basic guidelines for future educational policy must not be guided solely by profitability and efficiency to maintain the existing school network and to reduce it in the border municipalities, but by interests that will enable the realization of the principle of justice in education and dispersed school networks in the Borderlands, thus providing an opportunity for its sustainable development.

The processes of lead electrodeposition from electrolytes of various concentrations of sodium nitrate as the supporting electrolyte have been examined by chronoamperometry and by the scanning electron microscopic (SEM) analysis of deposits obtained in the potentiostatic regime of electrolysis. The good agreement between the diffusion coefficents determined by Cottrell equation and non-linear fitting method was observed. For the first time, the transition from the mixed ohmic-diffusion to the full diffusion control was defined from the analysis of Cottrell equation. The parameters, such as the number density of active sites and the nucleation rate constant, obtained by non-linear fitting method were discussed in accordance with the fact that lead belongs to the group of metals characterized by the high values of the exchange current density. The data obtained by the chronoamperometric analysis were succesfully correlated with morphologies of electrodeposited lead obtained in the different types of electrodeposition control. [Projekat Ministarstva nauke Republike Srbije, br. 172046]

Air-cooled condensers in thermal power plants have recently become increasingly popular. Besides all the advantages they have, like no demands for water supply on the plant site and no need for taking care of environmental regulations, they also have some serious disadvantages. One of the biggest disadvantages air-cooled condensers do have is precisely the nature of the Earth's atmosphere being their low temperature reservoir. Low density and low heat capacity of the air as the cooling medium combined with extremely stochastic behavior of the atmosphere itself put some serious challenges in front of the air-cooled condenser's proper and steady functioning. In this paper, the operating parameters of the air-cooled condenser in the chosen thermal power plant were investigated to gain a clearer insight into the influence of the atmospheric changes on its entropy generation and consequently on its efficiency. Also, the acquired results were further proposed as a starting point for potential optimization of the process inside the device. [ABSTRACT FROM AUTHOR]