Ocene stanja i tendencije u razvoju konkurentnosti privrede Srbije

Intenziviranje međunarodne razmene, razvoj tehnologije i pojava na globalnom tržištu agresivne konkurencije menjaju pravila igre i pozicije koje pojedini izvori imaju u kreiranju konkurentske prednosti na svetskom tržištu. Tehnološki razvoj, inovacije, znanje i veštine postaju faktori od krucijalnog značaja za razvoj jedne ekonomije i njenih preduzeća. Pod uticajem velikog broja faktora ekonomske i neekonomske prirode, oporavak i razvoj naše privrede ne odvija se očekivanom brzinom i lakoćom. Srbija se i nakon sprovedenih reformskih promena i dalje ne može pohvaliti dostignutim nivoom razvoja, kao ni konkurentskom pozicijom na svetskom tržištu. Imajući u vidu da je uključivanje u globalne svetske tokove i dalje prioritetni cilj ekonomske politike i da će se u tom pravcu preduzimati konkretnije mere, realno je očekivati intenzivniji razvoj privrede Srbije u narednom periodu. Stvaranjem konkurentnog ambijenta i definisanjem jasnih pravila igre za sve učesnike na tržištu, kreira se stimulativno poslovno okruženje u kome glavnu ulogu i odgovornost za uspehe i neuspehe na svetskom tržištu preuzimaju privredni subjekti, odnosno menadžment preduzeća. Konkurentnost naše privrede u velikoj meri biće determinisana znanjem i veštinama menadžera, odnosno mogućnostima da se proaktivno reaguje na dešavanja u okruženju, strategijski razmišlja i deluje

The influence of modification methods on physico-chemical and sorption properties of sepiolite Umnoženo za odbranu.

Predmet ove doktorske disertacije je proučavanje uticaja modifikacije prirodnog sepiolita primenom soli N-[(3-trimetoksi)propil]etilendiamintriacetatne kiseline ((CH3O)3Si(CH2)3N(CH2COONa)N(CH2)2N(CH2COONa)2), [3-(2- aminoetilamino)propil]trimetoksisilana ((CH3O)3Si(CH2)3NH(CH2)2NH2)), 3- merkaptopropiltrimetoksisilana (HS(CH2)3Si(OCH3)3) i gvožñe(III)-hlorida u baznoj sredini na fizičko-hemijska svojstva sepiolita, kao i na sorpciju Cu2+, Co2+ i Ni2+ jona iz vodenih rastvora i sorpciju organskih jedinjenja iz gasovite faze. Karakteristično svojstvo površine, tačka nultog naelektrisanja, pHtnn, odreñena je u rastvoru elektrolita različite koncentracije, kao i u prisustvu jona Cu2+, Co2+ i Ni2+. Utvrñeno je da se tačka nultog naelektrisanja ne menja sa promenom koncentracije rastvora KNO3, dok se u prisustvu Cu2+, Co2+ i Ni2+ jona pomera ka nižim pH vrednostima, što ukazuje na specifčnu sorpciju jona. Postupak modifikacije prirodnog sepiolita merkapto-silanom i amino-silanom nije doveo do povećanja sorpcije jona. Uzorak modifikovan oksidom gvožña pokazao se kao efikasan sorbent u sorpciji Cu2+, Co2+ i Ni2+ jona, dok je u slučaju modifikacije vodenim rastvorom natrijumove soli N-[(3-trimetoksi)propil]etilendiamintriacetatne kiseline uočen porast sorpcionog kapaciteta za Ni2+ jone. Sorpcija jona Cu2+, Co2+ i Ni2+ iz vodenog rastvora rezultat je istovremenog odigravanja procesa jonske izmene sa Mg2+ jonima iz sepiolitske strukture i specifične sorpcije. Poreñenjem maksimalnih sorpcionih kapaciteta utvrñeno je kod svih ispitanih sorbenata najveća sorpcija Cu2+ jona, zatim Co2+ jona a najmanja sorpcija Ni2+ jona. Proces sorpcije ispitanih jona na prirodnom, kao i na modifikovanim sepiolitima najbolje se opisuje Langmuir-ovom izotermom. Promena pH vrednosti, u oblasti u kojoj ne dolazi do rastvaranja sorbenta i hidrolize jona, nije bitno uticala na količinu sorbovanih jona na prirodnom sepiolitu, kao ni na modifikovanim uzorcima. Sorpcija jona Cu2+, Co2+ i Ni2+ jona raste sa porastom temperature. Pozitivne vrednosti promene entalpije sorpcije pokazuju da je sorpcija endoterman proces. Ispitivanje kinetike sorpcije, pri istoj polaznoj koncentraciji jona metala pokazalo je da kinetički model pseudo-drugog reda najbolje opisuje eksperimentalne rezultate, za sve ispitane sorbente. Vrednosti konstanti jonizacije uzorka sepiolita modifikovanog gvožñe(III)- hloridom u baznoj sredini (Fe-SEP) iznose: p 1 int a K = 6,7 ± 0,1 i p 2 int a K = 10,2 ± 0,1. Uzorak ima veću relativnu kiselost površinskih funkcionalnih grupa u odnosu na prirodni sepiolit, usled prisustva gvožñe(III)-oksihidroksida u strukturi modifikovanog sepiolita. Primenom inverzne gasne hromatografije u uslovima nulte prekrivenosti u temperaturnom opsegu 483-513 K izračunate su vrednosti osnovnih termodinamičkih parametara adsorpcije (slobodne površinske energije, standardne entalpije i standardne entropije adsorpcije) na uzorku Fe-SEP, kao i specifična i disperzivna komponenta slobodne energije adsorpcije. Rezultati ispitivanja interakcija uzorka Fe-SEP i kiselih, baznih i amfoternih organskih molekula pokazali su da je površina ispitanog uzorka baznog karaktera. Na osnovu dobijenih adsorpcionih izotermi za n-heksan, benzen, hloroform i tetrahidrofuran na sepiolitu Fe-SEP primenom inverzne gasne hromatografije u uslovima konačne prekrivenosti u temperaturnom opsegu 483-513 K i B.E.T. jednačine izračunate su vrednosti specifične površine, izosterične toplote adsorpcije, kao i raspodela adsorpcione energije. Površina sepiolita pokazuje povećani afinitet prema hloroformu usled uspostavljanja jakih kiselo-baznih interakcija.The aim of this study was to investigate the influence of modification of natural sepiolite using: 3-mercaptopropyltrimethoxysilane (HS(CH2)3Si(OCH3)3), [3-(2- aminoethylamino)propyl]trimethoxysilane ((CH3O)3Si(CH2)3NH(CH2)2NH2)), N-[3- (trimethoxysilyl)propyl], ethylenediamine triacetic acid trisodium salt ((CH3O)3Si(CH2)3N(CH2COONa)N(CH2)2N(CH2COONa)2) and iron(III)chloride in basic conditions, on physico-chemical properties, sorption of Cu2+, Co2+ and Ni2+ ions from water solutions and sorption of organic molecules from the gas phase. The point of zero charge, pHtnn, as an important surface parameter, was determined in electrolyte solutions with different initial concentration and in the solution of M2+ ions. The value of pHtnn remains constant with changing concentration of the KNO3 solution. The shift of the point of zero charge of sepiolite samples was determined in the presence of Cu2+, Co2+ and Ni2+ ions indicating that specific sorption of M2+ ions onto sepiolite samples had occurred. The improvement of the sorption efficiency of samples obtained by modification of sepiolite with mercapto-silane and amino-silane was not observed. Modification of natural sepiolite by iron oxyhydroxide resulted in formation of an effective sorbent for sorption of Cu2+, Co2+ and Ni2+ ions, while in the case of modification by ethylenediamine triacetic acid trisodium salt from water solution, the increase of sorption capacity was deteced for sorption of Ni2+ ions. The sorption of Cu2+, Co2+ and Ni2+ ions from water solutions is the result of the process of ion exchange of Mg2+ ions from the sepiolite structure and specific sorption. According to maximal sorption capacities, the sorption was the highest in the case of Cu2+ ions, then Co2+, and the lowest in case of Ni2+ ions, for used all sorbent. The equilibrium sorption process, for all investigated ions, on natural, as well as on modified samples, was well described by the Langmuir isotherm model. The change of the initial pH value, in the pH range where sorbent dissolution and hydrolysis of ions can be excluded, did not affect the change of capacities of sorption, on natural, as well on modified samples. The quantity of sorbed Cu2+, Co2+ and Ni2+ ions increased with increasing temperature. The positive enthalpy change indicates that the process of removal of M2+ ions from water solution by sepiolites was endothermic. The sorption kinetic study showed that pseudo-second order was the model that best described the experimental sorption data for all investigated ions and all the sorbents used, indicating that the sorption may be controlled by chemical sorption. The ionization constants of the surface functional groups of sepiolite modified with iron(III)chloride in basic conditions (Fe-SEP) determined from the potentiometric titration data, were p int a1 K = 6.7 ± 0.1 and p int a2 K = 10.2 ± 0.1. The relative acidity of the surface functional groups was lower comparing to natural sepiolite sample, that can be assigned to the presence of iron oxyhydroxide particles at the surface of modified material. The thermodynamic parameters (free energy, enthalpy, entropy) of adsorption as well as dispersive and specific components of free energy of adsorption were calculated from the inverse gas chromatography measurements for the probes on the sample Fe- SEP in temperature range 483-513K. The results of interactions of Fe-SEP amd bacis, acid and amphoteric organic probes indicate that Fe-SEP surface has basic character. The sorption isotherms for n-hexane, benzene, chloroform and tetrahydrofurane, on sample Fe-SEP, determined by inverse gas chromatography at finite concentration condition in the temperature range 483-513 K, were used to estimate the surface area, isosteric heat of adsorption and adsorption energy distribution function. The strong interaction between Fe-SEP surface and chloroform, due to acid-base interactions, was established

Creative Cash Flow Reporting – the Motivation and Opportunities

Company's stakeholders make business decisions based on information presented by management. The quality of decisions, among other things, depends on the quality and reliability of information in the financial reports. Business practice demonstrates that managers tend to present a false picture of the financial position and profitability of the company, often in cooperation with the owners of the capital. Procedures that management and investors take, in order to create a false impression about the performances of the enterprise, the contemporary literature defines as creative financial reporting. Presentation of better financial performance than realistic one provides misleading signals about the company, while the users of information are misinformed. The goal of this paper is the analysis of opportunities to implement creative cash flow reporting and the factors that encourage the company’s management and the owners of the capital to wrong and misleading interpretation of performance items. After the presentation of the main motive of creative financial reporting, we shall focus on examples of erroneous classification of cash flows. Earnings management and the shaping of cash flows may be realised within and beyond the boundaries of accounting regulations on several ways, but a special review in the paper is dedicate to creative reporting procedures of cash inflow and outflow related to receivables, investments, liabilities, and expenses. Consequences of creative reporting on cash flow and other performances could be serious both for stakeholders and for survival of the company, which is discussed in the last part of the paper

Specifics of Management in Small and Medium-Size Enterprises in Serbia

Under modern conditions for performing business, an enterprise regardless of its size or business activity must be systematically directed and run. Small and medium-size enterprises have certain characteristics that make them considerably different compared to large systems, therefore it is not realistic to expect that the management process in such organizations would develop in the same way as in the large systems. The fact is that the small business often does not involve a small investment, and the management of small enterprises is constantly faced with the problem of "poverty of resources" that leads to the conclusion that the success of SMEs is predominantly determined by the managerial skills of managers/owners. Assuming that the owners/managers of SMEs adequately perceive the capabilities of their enterprise, make the right decisions, finding effective solutions in terms of organization and apply modern approaches to control and the success of the company definitely will follow. In this paper theoretical and empirical research has been carried out with the aim to identify the basic characteristics of successful management of SMEs in Serbia. The research results indicate that the managerial capacity of managers/owners of SMEs is the main strength of the company, and one of the key sources of growth and development. When the influence of external factors is very unfavorable for business development, the management as an internal resource of organization is increasingly gaining importance in creating business success and competitive advantage

Uticaj prirodnih biostimulatora i spororazlagajućih đubriva u komercijalnoj proizvodnji rasada begonija (Begonia semperflorens)

The present research in the study of the effect of application of natural bio-stimulants and slow-release fertilizers on commercial production of begonia (Begonia semperflorens) saplings. Two types of containers were deployed in the production process, whereas the results of the experimental research showed that the application of both slow-release fertilizers and natural bio-stimulants in further production is only justifiable in cases when large volume containers are deployed in commercial production of sapling. The application of those significantly influences the increase in stalk weight, number of sprouts and number of blossoms. The application of natural bio-stimulants may be justifiable with the saplings that have previously been produced in smaller containers, since they have auspicious effect upon development of the root, i.e. upon its length.U radu je ispitivan uticaj primene prirodnih biostimulatora i spororazlagajućih đubriva u komercijalnoj proizvodnji rasada begonija (Begonia semperflorens ).Za proizvodnju rasada korišćeno je dva tipa kontejnera a dobijeni rezultati eksperimentalnih istraživanja pokazali su da je primena i spororazlagajućih đubriva i prirodnih biostimulatora u toku dalje proizvodnje , opravdana samo u slučaju kada se za proizvodnju rasada koriste veći kontejnerima. Njihovom primenom utiče se značajno na povećanje nadzemne mase, broja pupoljaka i broja cvetova. Primena prirodnih biostimulatora može biti opravdana i kod proizvodnje rasada u manjim kontejnerima jer povoljno utiče na razvoj korena tj. njegovu dužinu

Carbon Cryogel Magnetite Composites-Effective Adsorbents for the Phosphate and Phenol Removal from Water

Carbon cryogel (CC) was impregnated with magnetite to produce a multifunctional magnetic adsorbent capable of removing phenoles and phosphates from water. Adsorbents were prepared via co-precipitation of Fe2+ and Fe3+ ions in aqueous solution in the presence of CC. Non-treated or acid-activated CC was used. The CC: Fe3O4 ratios of 1:1 and 3:1 were applied. The addition of HCl in the synthesis process was also investigated. XRD confirmed the formation of nanocrystalline magnetite. BET analysis showed that the pre-treatment diminished the CC porous structure, reducing also specific surface area (Sp). Formation of magnetite decreases Sp and total volume of micro and meso pores, but their distribution remained unchanged. FTIR spectra revealed that magnetite was attached to the surface of the acid activated CC via C═O bond. DTA-TGA and SEM indicated that acid treatment and presence of HCl were beneficial for homogeneous nucleation and distribution of magnetite, increasing adsorption properties of composite. Batch adsorption proved that the maximum adsorption capacity for phenoles was accomplished with 3:1 ratio with non-treated CC. Samples synthesized with pre- treated CC, under 1:1 ratio, gave the best results for phosphate removal. The CC/magnetite composite was found as promising adsorbent for the simultaneous removal of both polutants.The book of abstract available at: [http://conf.univerzitetpim.com/wp-content/uploads/2022/06/Book-of-Abstracts_2022-1.pdf

Use of sintering to immobilize toxic metals present in galvanic sludge into a stabile glass-ceramic structure

Galvanization process requires the use a large amount of water and produces wastewaters that are usually purified by conventional cost-effective procedure. This kind of treatment generates waste sludge which becomes a hazardous if is not properly stabilized. Hence, the aim of this paper is to investigate the characteristics of galvanic sludge through the inspection of its physicochemical parameters and consider stabilization of waste materials, including waste glass and aluminum slag by their conversion into an eco-designed material referred to as glass ceramics. The obtained products have been studied by X-ray diffraction (XRD). XRD analyses confirmed occurrence of chemical and phase transformations in treated galvanic sludge and binding of toxic metals (Al3+, Cr3+, Cu2+, Cd2+, Ni2+, Pb2+, Zn2+) into crystalline phases and very sTab. structure.Процес галванизације захтева велику количину технолошке воде што има за последицу стварање отпадних вода, које се из економских разлога пречишћавају конвенционалним системима. Овим третманом настаје отпадни муљ који, уколико се адекватно не стабилизује, представља опасан отпад. У том смислу, у раду је извршена карактеризација галванског муља анализом физичкохемијских параметара компонената, а затим стабилизација ових отпадних материја, укључујући отпадно стакло и алуминијумску шљаку, превођењем у еко-синтеровани материјал стаклокерамика. Добијени производ анализиран је рендгенском дифракционом анализом (XRD). На основу XRD спектра потврђене су хемијско-фазне трансформације третираног галванског муља и везивање токсичних метала (Al3+, Cr3+, Cu2+, Cd2+, Ni2+, Pb2+, Zn2+) у веома стабилну кристалну структуру

Determination of the lipophilicity of 2҆'-Hydroxychalcones by RP-HPLC method [Određivanje lipofilnosti 2'-hidroksihalkona primenom RP-HPLC metode]

Lipophilicity of twelve synthesized chalcones, whose ring B is a ortho, meta or para monosubstituted with alkyl, oxyalkyl groups or halogens was determined by reverse phase liquid chromatography, using octadecyl-functionalized (RP-18) silica gel as a stationary phase and two-component mixture of methanol/water as a mobile phase. Linear dependence of log k' values of the volume fraction of methanol in the mobile phase was determined for all analyzed compounds, with high coefficient of correlation (r > 0.99). Extrapolation of the line to 0% methanol concentration resulted in the capacity factor of chromatographic system where water is the mobile phase (log k(w)). For five standard substances, chemically similar to chalcones, log kw values were determined under experimental conditions and they were correlated with logP values of those compounds available in the literature. log P-EXP values of synthesized chalcones were calculated on the basis of the created standard curve. In order to estimate the relevance of the experimentally obtained log P values for chalcones, correlation of log P-EXP values with the log P values obtained through various computational procedures was performed using linear regression analysis. Statistical parameters of dependence showed that the best matching of the results had been achieved with ChemOffice program, suggesting that this program is suitable for calculating logP values of newly-synthesized chalcones, as well as of compounds structurally similar to chalcones

The effect of sulfuric acid treatment on physicochemical properties of g-C3N4 and its efficiency for photocatalytic reduction of Cr(VI)

A great deal of interest is directed towards g-C3N4 (CN) for the photocatalytic reduction of Cr(VI), due to its high stability in acidic conditions and medium band gap (~2,7 eV), but its practical application is limited because of the high recombination rate of electrons and holes. Sulfuric acid treatment is considered as one of the methods for optimizing properties of CN by certain surface and possibly structure modifications which would lead to an increased specific surface area (Sp) and more active sites, anchoring electronegative groups to enhance charge separation, exfoliated bulk CN into the nanosheets, etc. The aim of this research was to investigate the influence of H2SO4 concentration and other experimental conditions (temperature and time) on physicochemical properties and photocatalytic efficiency of CN.ExcellMater Conference 2024: Innovative Biomaterials for Novel Medical Devices, Belgrade, Serbia, April 10-12, 202

Supplementary material for the article: Čolić, S. D.; Fotirić Akšić, M. M.; Lazarević, K. B.; Zec, G. N.; Gašić, U. M.; Dabić Zagorac, D. Č.; Natić, M. M. Fatty Acid and Phenolic Profiles of Almond Grown in Serbia. Food Chemistry 2017, 234, 455–463. https://doi.org/10.1016/j.foodchem.2017.05.006

Supplementary material for: [https://doi.org/10.1016/j.foodchem.2017.05.006 ]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2473]Related to accepted version: [http://cherry.chem.bg.ac.rs/handle/123456789/3215