Infrastructure and service providing companies business activities

In general, the end of the 20th and the beginning of the 21 century is marked by the growing role of services and service organizations. The new technology development and changes in life style increase the importance of services and service organizations dependence on infrastructure development level. The impact of infrastructure is becoming more and more important for service companies development. The infrastructure-growing role is especially emphasized in service sector, because it has a great influence on scope and quality of entrance (spent factors) and exit in service making process and service organizations business activities. The research results, presented in this paper, indicate that various intensity of infrastructure impact service organizations productivity. The infrastructure impact intensity on service organizations productivity depends on many factors such as: main characteristics of services, local and regional characteristics, technical progress level, economic structure, prevailing demand etc. The modern technologies development enlarges the services dependence on infrastructure

Modeliranje sezonskih promena temperature vode akumulacije Ćelije

This paper presents the results of measurements and numerical modeling of water temperature changes in reservoir Celije in the period from April to October 2012. Reservoir Celije on the river Rasina, for many years attracts the attention of the general public and researchers, due to the importance of water management and impact of wastewater from the upper part of the basin. Reservoir Celije is a major source of PUC Krusevac Waterworks, but is also the recipient of municipal and industrial wastewater from the municipalities of Brus and Blace. Paper uses a two-dimensional model (CE QUAL W2), with transverse averaged hydrodynamic equations for the velocity and temperature field modeling in the vertical longitudinal plane. Data on the water temperature were collected in the field sampling campaigns, using multi - parameter probes. Model calibration enabled good comparison of measured and calculated temperatures, with average absolute deviation of about 0.7oC. For enhanced model performance, it would be necessary to reduce the uncertainty of the input data, which can be achieved by re- commissioning of the measuring station Ravni (upstream of the reservoir) and setting automatic weather station in the vicinity of the barrier.U radu je dat prikaz rezultata merenja i modeliranja sezonskih promena temperature vode u akumulaciji Ćelije u periodu od aprila do oktobra 2012. godine. Akumulacija Ćelije na Rasini, već duži niz godina privlači pažnju šire javnosti i istraživača, obzirom na vodoprivredni značaj i stepen ugroženosti otpadnim vodama iz gornjeg dela sliva. Akumulacija Ćelije je glavno izvorište kruševačkog vodovoda, ali je ujedno i recipijent komunalnih i industrijskih otpadnih voda iz opština Brus i Blace. U radu je korišćen dvodimenzionalni model (CE QUAL W2), sa poprečno osrednjenim hidrodinamičkim jednačinama za modeliranje polja brzina i polja temperatura u vertikalnoj podužnoj ravni. Podaci o temperaturi vode su prikupljeni u kampanjama terenskih merenja, primenom multiparametarskih sondi. Kalibracijom modela, postiglo se dosta dobro poklapanje izmerenih i izračunatih temperatura, sa prosečnim apslutnim odstupanjem od oko 0,7oC. Za unapređen učinak modela, potrebno bi bilo smanjiti neodređenost ulaznih podataka, što bi se postiglo ponovnim puštanjem u pogon merne stanice Ravni (uzvodno od akumulacije) i postavljanjem kompletne automatske meteorološke stanice u blizini pregradnog profila

Lateral-Directional Aerodynamic Optimization of a Tandem Wing UAV Using CFD Analyses

This paper presents the second stage of a tandem fixed-wing unmanned aerial vehicle (UAV) aerodynamic development. In the initial stage, the UAV was optimized by analyzing its characteristics only in symmetrical flight conditions. Posted requirements were that both wings should produce relevant positive lift, the initial stall must occur on the front wing first, the center of pressure should be close to the center of gravity, and longitudinal static stability should be in the optimum range. Computational fluid dynamic (CFD) analyses were performed, where the applied calculation model was derived from the authors’ previous successful projects. The eighth version TW V8 has satisfied all longitudinal requirements. Lateral-directional CFD analyses of V8 showed that the ratio of the lateral and directional stability at the nominal cruising regime was optimal, but both lateral and directional static stabilities were too high. On further development versions, the lower vertical tail was eliminated, a negative dihedral was implemented on the front wing, and four inverted blended winglets were added. Version TW V14 has largely improved lateral and directional stability characteristics, while their optimum ratio at the cruising regime was preserved. Longitudinal characteristics were also well preserved. Maximum lift coefficient and lift-to-drag ratio were increased, compared to the V8

Potentials for tourism development based on protected natural resources in Moravica administrative district territory: Opinion of the city of Čačak residents

The purpose of this paper is to indicate the potentials for tourism development based on the protected natural resources of the Republic of Serbia situated in the Moravica administrative district territory, the degree of their current utilization for the purposes of tourism and local population information on the above mentioned. Closed-ended survey was conducted (five-point scale) on the random sample of the residents in the urban part of the city of Čačak as the administrative center of the Moravica administrative district. The results are: 1) low degree of information among the local population, 2) medium (good) potential for tourism development, and 3) very low level of its utilization for tourism purposes. The results are also considered according to the natural resources protection type. The contribution of this paper is in the indication of potentially successful elements in future tourism offer for the entities in the field of tourism and hospitality.Publishe

Multi-criteria decision making trends in ecotourism and sustainable tourism

The goal of this paper is to provide a comprehensive overview of application of multi-criteria decision making (MCDM) methods in papers from the field of ecotourism and sustainable tourism. A search has been done of the relevant terms in titles, abstracts and keywords found in papers from 26 prominent journals from the field of tourism belonging in Web of Science (WoS) Clarivate Analytics. It has been established which MCDM methods were used and who are the most common authors of such papers. A keyword frequency analysis was also performed. It is established there are 39 papers in the field of ecotourism and sustainable tourism where MCDM methods were applied whereby all were published after the year 2000, as well as that their number is constantly increasing.Publishe

Analiza uticaja izgradnje sistema HE na Ibru na kvalitet vode

Water quality impact assessment of the River Ibar hydropower cascade project is analyzed in this paper, as one of possible aspects of environmental impact assessment. Based on available data provided by authorized institutions, the current state of River Ibar ecological and chemical status is determined in accordance with the methodology prescribed by legislation. The ecological status of the water course between Raska and Kraljevo is rated as moderate, with evaluation considered as reliable. At the same time, the chemical status is rated as good. Quantitative assessment of possible impacts on water quality is conducted by dual approach: 1) application of hydrodynamic model, utilized for analysis of possible thermal regimes in cascade reservoirs, and 2) application of the 'method of analogy' to the existing, well studied reservoir 'Celije', the reservoir with similar morphological characteristics and water quality conditions at the entrance of the system. Results indicate that future cascade reservoir system will represent a number of aquatic ecosystems that will perform as a transitional form between river and lake systems. From the environmental perspective, it is important that thermal stratification of reservoirs during the warm seasons is not expected to be established. Consequently, the eutrophic potential of the River Ibar, based on significant content of macroelements in water, is not expected to be fully realized.U radu su analizirani mogući uticaji izgradnje kaskade protočnih hidroelektrana na deonici reke Ibar između Raške i Kraljeva na kvalitet vode, kao jedan od mogućih aspekata uticaja ovih objekata na životnu sredinu. Analizom raspoloživih podataka o kvalitetu vode reke Ibar, najpre je urađena ocena ekološkog i hemijskog statusa. Utvrđeno je da se na posmatranom delu vodotoka ekološki status može ocenitiumerenim, pri čemu se ocena može smatrati pouzdanom, dok je hemijski status ocenjen dobrim. Kvantitativna procena uticaja na kvalitet vode je urađena primenom dvojnog pristupa: 1) primenom hidrodinamičkog modela sistema HE, kojim je simuliran očekivani termički režim u planiranim akumulacijama, i 2) primena 'metode analogije' u odnosu na procese koji su evidentiranina postojećoj akumulaciji 'Ćelije'. Rezultati ukazuju da će planirane akumulacije na Ibru predstavljati niz akvatičnih ekosistema koji će se ponašati i funkcionisati kao prelazni oblik između rečnih i jezerskih sistema. Pri tome, neće biti uslova za formiranje stabilne termičke stratifikacije vode u toplijem delu godine, što će usloviti nemogućnost potpune realizacije eutrofikacionog potencijala, koji nesumnjivo postoji, imajući u vidu sadržaj makroelemenata u vodi reke Ibar u postojećim uslovima

Analiza uticaja izgradnje sistema HE na Ibru na kvalitet vode

Water quality impact assessment of the River Ibar hydropower cascade project is analyzed in this paper, as one of possible aspects of environmental impact assessment. Based on available data provided by authorized institutions, the current state of River Ibar ecological and chemical status is determined in accordance with the methodology prescribed by legislation. The ecological status of the water course between Raska and Kraljevo is rated as moderate, with evaluation considered as reliable. At the same time, the chemical status is rated as good. Quantitative assessment of possible impacts on water quality is conducted by dual approach: 1) application of hydrodynamic model, utilized for analysis of possible thermal regimes in cascade reservoirs, and 2) application of the 'method of analogy' to the existing, well studied reservoir 'Celije', the reservoir with similar morphological characteristics and water quality conditions at the entrance of the system. Results indicate that future cascade reservoir system will represent a number of aquatic ecosystems that will perform as a transitional form between river and lake systems. From the environmental perspective, it is important that thermal stratification of reservoirs during the warm seasons is not expected to be established. Consequently, the eutrophic potential of the River Ibar, based on significant content of macroelements in water, is not expected to be fully realized.U radu su analizirani mogući uticaji izgradnje kaskade protočnih hidroelektrana na deonici reke Ibar između Raške i Kraljeva na kvalitet vode, kao jedan od mogućih aspekata uticaja ovih objekata na životnu sredinu. Analizom raspoloživih podataka o kvalitetu vode reke Ibar, najpre je urađena ocena ekološkog i hemijskog statusa. Utvrđeno je da se na posmatranom delu vodotoka ekološki status može ocenitiumerenim, pri čemu se ocena može smatrati pouzdanom, dok je hemijski status ocenjen dobrim. Kvantitativna procena uticaja na kvalitet vode je urađena primenom dvojnog pristupa: 1) primenom hidrodinamičkog modela sistema HE, kojim je simuliran očekivani termički režim u planiranim akumulacijama, i 2) primena 'metode analogije' u odnosu na procese koji su evidentiranina postojećoj akumulaciji 'Ćelije'. Rezultati ukazuju da će planirane akumulacije na Ibru predstavljati niz akvatičnih ekosistema koji će se ponašati i funkcionisati kao prelazni oblik između rečnih i jezerskih sistema. Pri tome, neće biti uslova za formiranje stabilne termičke stratifikacije vode u toplijem delu godine, što će usloviti nemogućnost potpune realizacije eutrofikacionog potencijala, koji nesumnjivo postoji, imajući u vidu sadržaj makroelemenata u vodi reke Ibar u postojećim uslovima

Recovering the Soybean Hulls after Peroxidase Extraction and Their Application as Adsorbent for Metal Ions and Dyes

This study is aimed at extending the soybean hulls' lifetime by their utilization as an adsorbent for metal ions (Cd2+ and Cu2+) and dyes (Reactive Yellow 39 (RY 39) and Acid Blue 225 (AB 225)). ATR-FTIR spectroscopy, FE-SEM microscopy, and zeta potential measurements were used for adsorbent characterization. The effect of the solution's pH, peroxidase extraction, adsorbent particle size, contact time, the pollutant's initial concentration, and temperature on the soybean hulls' adsorption potential was studied. Before peroxidase extraction, soybean hulls were capable of removing 72% Cd2+, 71% Cu2+ (at a pH of 5.00) or 81% RY 39, and 73% AB 225 (at a pH of 3.00). For further experiments, soybean hulls without peroxidase were used for several reasons: (1) due to their observed higher metal ion removal, (2) in order to reduce the waste disposal cost after the peroxidase (usually used for wastewater decolorization) extraction, and (3) since the soybean hulls without peroxidase possessed significantly lower secondary pollution than those with peroxidase. Cd2+ and Cu2+ removal was slightly increased when the smaller adsorbent fraction (710-1000 μm) was used, while the adsorbent particle size did not have an impact on dye removal. After 30 min of contact time, 92% and 88% of RY 39 and AB 225 were removed, respectively, while after the same contact time, 80% and 69% of Cd2+ and Cu2+ were removed, respectively. Adsorption of all tested pollutants follows a pseudo-second-order reaction through the fast adsorption, intraparticle diffusion, and final equilibrium stage. The maximal adsorption capacities determined by the Langmuir model were 21.10, 20.54, 16.54, and 17.23 mg/g for Cd2+, Cu2+, RY 39, and AB 225, respectively. Calculated thermodynamic parameters suggested that the adsorption of all pollutants is spontaneous and of endothermic character. Moreover, different binary mixtures were prepared, and the competitive adsorptions revealed that the soybean hulls are the most efficient adsorbent for the mixture of AB 225 and Cu2+. The findings of this study contribute to the soybean hulls' recovery after the peroxidase extraction and bring them into the circular economy concept

Addressing the environmental problems of wastewater: reducing the pollution while providing multifunctional wool fabrics

The reduction of water pollution represents one of the priority topics of the EU’s goal to achieve climate neutrality by 2050. Considering this, the concept of reusing the same dyebath for multiple dyeing cycles is proposed. For this purpose, two pyridinium-based azo pyridone dyes with improved solubility and affinity towards different fibers, are used for dyeing wool fabric. It is demonstrated that the dye concentration in wastewater could be reduced up to four times by recirculation of the same dyebath 5 times. The dyed fabrics obtained in each cycle are further characterized regarding color strength (K/S) and ultraviolet protection factor (UPF), while their antioxidant potential is evaluated by ABTS (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) test. The results revealed that the proposed concept could be used for obtaining multifunctional wool fabrics by following the principles of sustainable development of reducing the effluent load in wastewater