Possibilities and constraints of application of the WERA method for risk assessment associated with VDT work

The WERA is a relatively new method, which has been used for assessment of risk factors, associated with work-related musculoskeletal disorders. The method was tested previously at the plasterer workplace by the authors of this method. Since there are no published data about the application of the WERA method on tasks where is dominant the static work, the authors of this paper consider that is of importance to examine the sensitivity of this method in occupations where is prevalent the static working activity, such as it is in the case of VDT work. VDT work is one of the activities that is performed in sitting position, which does not require special tools, and for which is characteristic certain static stress of large musculo - skeletal regions. Possibilities and constraints of the WERA method are examined in this preliminary study, which was performed on a relatively small group of VDT users

Greenways in Landscape Planning – Case Study: Municipality of Subotica

Municipality of Subotica is located at the northern part of the Vojvodina Province and Republic of Serbia, along the Hungarian border. The natural heritage of the Vojvodina Province (North part of Serbia) is extraordinary diverse with important ecosystem diversity. In the Vojvodina province there are extra natural and landscape areas specific for the South – East Europe as Deliblato sands (the biggest sand area in the Europe), hilly areas of Fruška Gora and Vršački breg. Also, the rivers Danube, Sava, Tisa, Begej, Tamiš and their floodplain zones (Apatinski rit, Monoštorski rit, Koviljski rit, Obedska bara, Carska bara, etc.), the steps zones in Middle and North Banat, loess area along the Tisa and Danube rivers (Titelski breg, Slanka men, Surduk). The protected areas on saline soils (Slano kopovo, Rusanda and Okanj) are also very important. The protected area network consists of about 200 spatial entities, which cover 5.5% of the total Province area (Orlović et al, 2005.). According to the Law of natural protection in municipality of Subotica there are four zones under special protection (Figure 1). Ludaš lake and Selevenj heath are strict nature reserves with total area of 846.33 ha (Official Gazette RS, 2006) and 677.04 ha (Official gazette RS, 1997), respectively. The areas are important due to rich diversity of lowland habitat types, as well as extremely high levels of floral diversity with a significant number of endangered species of authentic Pannonian flora and fauna. Ludaš lake also has an international significance (Ramsar wetland) because it represents a meeting place and place for rest of migratory bird species. Subotica sands is ranked as land of exceptional feature (5370 ha) which is characterized by unique environmental conditions, in terms of sand geological ground, variety of soil and special regime of ground water (Official Gazzete RS, 2004). The fourth area under special protection is nature park Palić with total area of 712.3 ha. Besides natural resources and the rich biodiversity, this area is also important for tourism development due to the numerous cultural value: the archaeological sites dating from the Stone Age and the Middle Age as well as examples of architecture in Art Nouveau style. There is also a large number of ethno houses showing the life, traditions and crafts typical for the northern Serbia. Construction of an international highway that passes through the region caused an additional pressure on the ecosystem of these areas. According to Ahern (1995): „greenways are networks of land containing linear elements that are planned, designed and managed for multiple purposes including ecological, recreational, cultural, aesthetic, or other purposes compatible with the concept of sustainable land use“. Ecological function of greenway is important, linking isolated areas and helping to improve local biodiversity in several ways: by allowing individual animals access to a larger area of habitat; facilitating seasonal migration and genetic exchange with other local populations of the same species; and offering opportunities for individuals to move away from a habitat that is degrading or from an area that is under threat (Benett and Mulongoy, 2006). Landscape connectivity is not only important because environment protection, but it also has social and cultural goals (Ahern, 1995). Greenways can develope activities, such as nature tourism, environmental education that will promote landscape sustainability and stimulate social, economic and ecological dynamics (Pena et al., 2010)

Heavy Metals Content in Foliar Litter and Branches of Quercus petraea (Matt.) Liebl. and Quercus robur L. Observed at Two ICP Forests Monitoring Plots

Background and Purpose: Due to the ability to uptake and accumulate heavy metals (HM) in their aboveground tissues, trees may be used for phytoremediation purposes, but also as bioindicators of environmental pollution. The aims of the present study were: a) to investigate the content and temporal variation of the studied HMs in different plant organs during the period of intensive leaf falling (September-October), in two species from genus Quercus; b) to evaluate the observed HMs content relative to plausible ranges of element concentration in foliar litter, as recommended by ICP Forests Foliar Co-ordinating Centre (IFFCC). Material and Methods: The contents of zinc (Zn), manganese (Mn), copper (Cu) and iron (Fe) were assessed in the litterfall (i.e. leaves and branches) of Quercus petraea (Matt.) Liebl. and Quercus robur L. grown at two ICP Forests Level II monitoring plots (Fruška Gora and Odžaci, Serbia). Plant material was sampled during September-October 2018 and analyzed by atomic absorption spectrophotometry. Results: Comparing the content of investigated HMs in foliar litter and branches of Q. robur and Q. petraea, notably higher concentrations of Mn and Fe have been observed in the foliage of both species, whereas Zn and Cu concentrations were higher in collected branch material of both of the above-mentioned tree species. The results further showed that, when compared to plausible ranges of element concentrations in foliar litter, given by ICP Forests Foliar Co-ordinating Centre (IFFCC), average concentrations of Fe and Zn in the leaves were within suggested limits, whereas certain concentrations of Mn and Cu exceeded the proposed ranges. Furthermore, the content of the studied HMs in plant material of both Quercus species significantly varied during sampling period. Conclusions: Although it was observed that concentrations of certain HMs were beyond plausible limits recommended by IFFCC, our results were in accordance with the findings of other authors who studied HMs content in Quercus species grown in natural forests. For that reason, these limits should be considered optionally, i.e. in the cases when the results significantly deviate from the suggested values. Moreover, we believe that the observed variation in the HMs content during sampling period is related to the sampling procedure commonly applied at ICP Forests monitoring plots, which is indirectly associated with the capacity of trees to accumulate HMs and their phenological properties

Hydrodesulfurization of light gas oil - kinetic determination in a batch reactor [Hidrodesulfurizacija lakog gasnog ulja - ispitivanje kinetike HDS u šaržnom reaktoru]

The performed investigations were directed toward the analysis of the performance and activity of the fresh and regenerated Cyanamid HDS 20C catalyst in a laboratory batch reactor (2 dm3) for the HDS of the diesel fraction (light gas oil, LGO). Testing of the regenerated catalyst was performed with light gas oil (LGO) of different characteristics. The determined values of the reaction rate constant were compared to some published data in the literature for the HDS of specific sulfur compounds as well as the values of the activation energy. The rates of deactivation of the fresh and regenerated catalyst actually existed compared to some other results recently published in the literature. However, such an observed differences were not sufficient to derive a relation which could be used for the determination of the rate of catalyst deactivation

Review of biodiesel synthesis from waste oil under elevated pressure and temperature: Phase equilibrium, reaction kinetics, process design and techno-economic study

The synthesis of biodiesel under elevated pressure and temperature could be promising technology which could result in sustainable biodiesel production, from renewable and waste streams like waste oil or used frying oil, thereby having no impact on biodiversity and the environment. This paper is comprehensive review of biodiesel synthesis from waste oil under elevated pressure and temperature: the supercritical or subcritical conditions of alcohol, with or without the use of heterogeneous catalyst. The review compromises the thermodynamic data, phase equilibria, phase composition and distribution during reaction, kinetic parameters and kinetic modeling, are presented. This type of data is necessary for process design and optimization. Process economics is analyzed and the impact of different production parameters (feedstock type, process parameters as temperature, pressure and alcohol to oil ratio, and different technology) is summarized and discussed

Rerafinacija otpadnih mineralnih transformatorskih ulja

Different physical and chemical processes taking place in the transformer or transformer insulation system, are influencing the decrease in the insulating oil quality. After certain period of time, the oil cannot meet the technical specifications, and drying and filtration cannot regenerate it. These spent transformer oils could be rerefined by solvent extraction, which yields a high quality transformer oil or high quality base oil for other applications. In this paper we present some of the basic characteristics of solvent extraction methods, their potential application for spent transformer oil rerefining and comparative characteristics of spent transformer oil, product of its rerefining and unused transformer oils.Tokom eksploatacije, usled fizičkih i hemijskih procesa koji se odigravaju u transformatoru i transformatorskoj izolaciji, dolazi do opadanja kvaliteta ulja. Nakon određenog perioda eksploatacije transformatorsko ulje više ne zadovoljava kriterijume zahtevane odgovarajućim standardima, i nije ga moguće regenerisati sušenjem i filtriranjem. Ovakva otpadna transformatorska ulja mogu se rerafinisati nekom od tehnologija solventne rerafinacije, pri čemu se kao proizvod dobija transformatorsko ulje visokog kvaliteta ili kvalitetno bazno ulje za druge oblasti primene. U radu su prikazane neke od osnovnih karakteristika tehnologija solventne rafinacije, kao i uporedni pregled kvaliteta otpadnih transformatorkih ulja, njihovih rerafinata i novih transformatorskih ulja

The Influence of Hydrodearomatisation Reaction Kinetics on the Modelling of Sulphur and Aromatics Removal from Diesel Fuel in an Industrial Hydrotreating Process

Over the years, the hydrotreating process has been considerably improved in order to facilitate the production of environmentally friendly diesel fuels by reducing sulphur and aromatics concentrations, as mandated by contemporary emissions regulations. In this study, different kinetic models for the hydrodearomatisation reaction and the influence of reaction rate on performance of the industrial trickle bed reactor for hydrotreating of gas oil and light cycle oil fractions were analysed. The impact on reactor temperature, catalyst wetting efficiency, and conversion of sulphur and aromatics were determined. The results of simulations were compared with experimental data from an industrial test run and the best model for the observed process is proposed. Reactor performance and overall efficiency of the process is strongly dependent on the kinetics of hydrodearomatisaton with respect to aromatics conversion but even more so with respect to the temperature increase in the reactor, which affects all key catalytic reaction parameters, catalyst wetting efficiency, and thus the sulphur conversion. Based on the obtained simulation results, it could be concluded that reactor performance is strongly dependent on the hydrodearomatisation reaction. The best predictions of outlet temperature as well as sulphur and aromatic conversion (deviation from the experimental value 0.87 K, 0.01% and 2.57%, respectively) are achieved with the Langmuir-Hinshelwood kinetic model proposed by Owusu-Boakye

Supercritical extraction of phloroglucinols from St. John's wort (Hypericum Perforatum L.) - Process optimization, mathematical modeling and antimicrobial activity

St. John's Wort (Hypericum perforatum L.) has been widely used as an anti-inflammatory and healing agent in traditional medicine. Some para-pharmaceutical products, prepared from the extract of St. John's Wort, are frequently used because of their anti-depressive and antiviral properties. Moreover, the extract prepared from St. John's Wort (H. perforatum L.) has been also reported to have an antimicrobial, anti-inflammatory, and healing effect. Thus, extraction of a specific component from St. John's Wort which gives a high yield of total extract and high content of desired pharmacological active compounds is obviously in focus of many research activities today. Despite the evident clinical effects, there is still a controversy regarding the active principle of the extracts. Some authors attribute the antidepressant activity to hypericin and its derivatives, whereas, other studies are in the favor of hyperforin. Hyperforin, as a phloroglucinol derivative is a relatively lipophilic compound which is susceptible to rapid thermal, light-induced and oxidative decomposition. Adhyperforin presents its methyl derivative. The supercritical fluid extraction (SFE) is an outstanding method for the extraction of natural agents and valuable components from plant materials, because heat-sensitive compounds can be extracted without any degradation, and in addition, it is an environmentally acceptable technology. Supercritical carbon dioxide (SCCO2) is the most useful supercritical fluid in the food industry, because it is non-toxic, non-explosive, and available in high (food grade) purity and can be removed from the extracted products without leaving any residue. The main goal of this study was oriented to the investigation of process optimization of the best extraction method applicable to intergradient in food and pharmaceutical industry - supercritical fluid extraction as well as the antimicrobial activity of obtained extracts. The first part of study will represent the literature review of St. John's Wort occurrence in nature, their health effects and medical and pharmaceutical use

Procesiranje čvrstih materijala natkritičnim fluidima

One of the most interesting areas of supercritical fluids applications is the processing of novel materials. These new materials are designed to meet specific requirements and to make possible new applications in Pharmaceuticals design, heterogeneous catalysis, micro- and nano-particles with unique structures, special insulating materials, super capacitors and other special technical materials. Two distinct possibilities to apply supercritical fluids in processing of materials: synthesis of materials in supercritical fluid environment and/or further processing of already obtained materials with the help of supercritical fluids. By adjusting synthesis parameters the properties of supercritical fluids can be significantly altered which further results in the materials with different structures. Unique materials can be also obtained by conducting synthesis in quite specific environments like reversed micelles. This paper is mainly devoted to processing of previously synthesized materials which are further processed using supercritical fluids. Several new methods have been developed to produce micro- and nano-particles with the use of supercritical fluids. The following methods: rapid expansion of supercritical solutions (RESS) supercritical anti-solvent (SAS), materials synthesis under supercritical conditions and encapsulation and coating using supercritical fluids were recently developed.Jedna od najinteresantnijih oblasti primene natkritičnih fluida je procesiranje novih tipova čvrstih materijala. Zahvaljujući svojim specifičnim karakteristikama, natkritični fluidi se mogu iskoristiti za dobijanje novih materijala sa osobinama znatno drugačijim nego kod konvencionalno dobijenih materijala. Ovi novi materijali su dizajnirani da zadovolje specifične zahteve i da omoguće nove primene u sledećim oblastima: farmaceutske hemikalije, heterogena kataliza, mikro i nano čestice za specijalne primene novi izolacioni materijali, superkapacitatori kao i druge tehničke primene novih materijala. Postoje dve osnovne mogućnosti primene natkritičnih fluida u procesiranju materijala: sinteza materijala pod natkritičnim uslovima i naknadno procesiranje dobijenih materijala uz pomoć natkritičnih fluida. Neke od sinteza materijala se odvijaju pod natkritičnim uslovima kao u slučaju poletilena niske gustine. Modifikacijom procesnih parametara moguće je modifikovati karakteristike natkritičnog fluida i na taj način promeniti karakteristike i strukturu dobijenog materijala. Materijali jedinstvenih struktura se mogu dobiti i u veoma specifičnim reakcionim uslovima kao što su na primer reverzne micele. Ovaj rad je svojim većim delom posvećen materijalima koji se nakon sinteze procesiraju uz pomoć natkritičnih fluida. Poslednjih godina razvijeno je nekoliko novih metoda za dobijanje mikro i nano čestica uz pomoć natkritičnih fluida. Ove nove metode kombinuju karakteristike visoke gustine i moći rastvaranja natkritičnih fluida, sa mogućnošću njihove velike promene redukcijom pritiska. Metode kao što su brza ekspanzija natkritičnih rastvora (RESS), natkritični anti solvent (SAS) sinteza pod natkritičnim uslovima i enkapsulacija, su poslednjih godina korišćene u procesiranju veoma različitih tipova i vrsta čvrstih materijala

Modelling of non-catalytic biodiesel synthesis under sub and supercritical conditions: The influence of phase distribution

Biodiesel, a mixture of fatty acid methyl esters, is widely used as renewable bio-based alternative fuel for internal combustion engines. Kinetic model of non-catalytic biodiesel synthesis at elevated temperature and pressure, based on triglycerides conversion, is presented in this study. The model was developed using experimental reaction data of non-catalytic biodiesel synthesis at 150 and 210 degrees C, and under pressures of 1.0 and 4.5 MPa, respectively. The phase transition during transesterification at different conditions (subcritical and supercritical) and limitations of mass transfer between two liquid phases were included in the model. This complex reaction was represented by kinetic model with three consecutive and parallel reversible reactions, while kinetic parameters were calculated using simplified procedure based on triglycerides conversion as the only variable. The developed model was found to fit the experimental data for triglyceride conversion with high accuracy