Razvoj metoda i algoritama za procenu performansi komunikacionih sistema primenom aproksimacija specijalnih funkcija

The intensive development of wireless communication systems has been accompanied by the need to develop methods and algorithms for implementing appropriate approximations of special functions in order to efficiently estimate the corresponding performance of these services through their application. In order to evaluate the behavior of digital communications systems, it is necessary to estimate standard performance measures for the observed wireless communications systems, various modulation types application, detection types, as well as channel models, and observe relations between performance and key values of system parameters. The analysis of the average bit error rate at reception for the applied modulation format is one of the tools for assessing service performance, that describes the nature of the wireless communication system in the best manner. In order to analytically evaluate the average bit error rate for the applied modulation format, it is necessary to perform the most accurate implementation of the approximation of special functions erfc(x), erf (x), Marcum Q, in the widest input range values. The dissertation will present composite methods of the special functions’ approximations. In addition to the simplicity of realization in approximating the observed functions, the aspect of robustness of approximations absolute and relative error values in a wide range of input parameters values will be considered. The advantages of the proposed solutions will be highlighted by direct comparison with the absolute and relative errors obtained by using the known special functions’ approximations from the literature. Furthermore, when transferring information through fading communication channels, for cases of application of proposed special functions’ approximations, it will be proved that system performance can be determined more easily by applying solutions proposed in the dissertation. In this way, it would be easier to determine the probability of the error of communication systems due to different types of fading existance in the channel. By comparing predicted values of the average bit error rate at reception, when transmitting signals through various communication channels medias, for cases of application of existing, previously proposed special functions’ approximations, with the average bit error rate at reception obtained by calculation based on the proposed approximation solutions, it will be shown that communication performances can be calculated more precisely. Proposed approximations could also be used in the source coding of the signal and could simplify design and realization of the quantizers

Repair of a damaged turbocharger

The turbocharger is among the highest quality assemblies for modern internal combustion engines. Its contribution to engine operation is immeasurable – it increases the power output of the engine while indirectly reducing fuel consumption. Like all devices, turbochargers require quality maintenance as they are susceptible to failure. Faulty turbochargers are either repaired or replaced with new ones. Repair ensures substantial financial savings. The paper presents the consequences of damage to the turbocharger and the process of its repair

BiFeO3 fine powder controlled hydrothermal process synthesis and characterization

From the technological point of view, the mutual control of electric and magnetic properties is an attractive possibility, but the number of candidate multiferroic materials is limited. One of the most studied of them, BiFeO3 , has critical conditions for synthesizing single phase since the phase temperature stability range is very narrow. Bismuth ferrite (BFO) particles were synthesized by controlled hydrothermal process, where the particles of small sizes and high purity were obtained. A fitting refinement procedure using the Rietveld method was performed. Bismuth ferrite crystallizes in the perovskite type structure (α-BiFeO3 ) with rhombohedral space group R3c. The effects of thermal treatment through applied hydrothermal method on the obtained BFO grains morphology were evaluated by SEM and TEM analyses.SEM analysis showed that grains are very well crystallized, with non- fragmented crystal flats. Individual particles HRTEM analysis confirmed the evidence of ultra-fine single crystal particles, with characteristic (012) crystal planes. Furthermore, HRTEM confirmed the existence of twin stacking faults responsible for synthesized fine particles enhanced magnetic properties. The EPR results suggested the existence and participation of electrons trapped by vacancies or defects. It has been proposed that the existence of Fe 3+−OV defect complex could be generated at elevated temperatures followed by formation of Fe 3+ ions, which intensely provide the local 3d moments.IX Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 20-21, 2021; Belgrad

Mikrotalasna tehnika u sintezi 2-piridona i jedinjenja na bazi 2-piridona

2-Pyridones are important heterocyclic compounds that are widely used in medical chemistry, and their various derivatives have significant biological and medical applications. In this paper, the synthesis of 2-pyridones as well as 2-pyridone-based compounds, such as 2-quinolones, using microwave assisted organic chemistry is reviewed. The review is divided in three parts. In the first part, microwave synthesis of 2-pyridones according to the type of condensation is discussed. In the second part, microwave assisted synthesis of 2-quionolones is listed. At the end of the review several examples of microwave synthesis of other 2-pyridone based compounds (ring fused W-substituted 2-pyridones) are given.Aromatična heterociklična jedinjenja predstavljaju veoma značajnu grupu jedinjenja zbog svoje biološke i medicinske primene. Šestočlana heterociklična jedinjenja koja sadrže azot (npr. piridini, piridoni, pirimidini, piperidini, piperazini) se puno koriste u medicini jer poseduju određena farmakološka svojstva, a poseban značaj imaju 2-piridoni i 4-piridoni. Derivati 2-piridona su posebno interesantni jer je 2-piridonska struktura prisutna u mnogim jedinjenjima prirodnog porekla od ko j i h mnoga poseduju biološku aktivnost. Zbog široke primene jedinjenja koja u sebi sadrže piridonsku strukturu razvijen je veliki broj postupaka za njihovu sintezu. Konvencionalni način izvođenja organskih sinteza podrazumeva zagrevanje spoljašnjim izvorima toplote pri čemu se toplota prenosi kondukcijom, što predstavlja spor i neefikasan metod prenosa energije, jer zavisi od toplotne provodljivosti materijala, pa je temperatura reaktora veća od temperature reakcione smeše. Nasuprot tome, mikrotalasno zračenje je efikasan izvor zagrevanja koji direktno prenosi energiju kroz interakciju sa polarnim molekulima prisutnim u reakcionoj smeši. Mikrotalasne sinteze se ubrajaju među metode koje poštuju principe takozvane 'zelene hemije' što predstavlja razlog više za ovakvo izvodjenje sinteza. U okviru rada dat je pregled sinteza 2-piridona i jedinjenja koja sadrže 2-piridonsko jezgro primenom mikrotalasne tehnike. Pregled obuhvata sinteze koje su izvršene kako u savremenim laboratorijskim mikrotalasnim reaktorima tako i one koje su izvršene u komercijalnim mikrotalasnim pećnicama za domaćinstvo. Takođe je ukazano na prednosti mikrotalasne sinteze u odnosu na konvencionalni način zagrevanja

The biosorption potential of waste biomass young fruit walnuts for lead ions: Kinetic and equilibrium study

The biosorption potential of waste biomass young fruit walnuts (YFW) as a low-cost biosorbent, processed from liqueur industry, for Pb(II) ions from aqueous solution was explored. The structural features of the biosorbent were characterized by FTIR spectroscopy, which indicates the possibility that the different functional groups may be responsible for the binding of Pb(II) ions from aqueous solution. The effects of relevant parameters such as pH (2 - 6), contact time (0 - 120 min), biosorbent dosage (2 - 20 g), initial metal ion concentration (10 - 120 mg dm-3), at a temperature of 25(C with stirring (120 rpm) and a constant ionic strength of 0,02 mol dm-3 were evaluated in batch experiments. The sorption equilibrium of Pb(II) ion (when 84 % of metal ions were sorbed at an initial concentration of 15 mg dm-3) was achieved within the pH range 4 - 5 after 50 min. Kinetic data were best described by the pseudo-second order model. Removal efficiency of Pb(II) ion rapidly increased with increasing biosorbent dose from 2.0 to 8.0 g per dm-3 of sorbate. Optimal biosorbent dose was set to 6.0 g per dm3 of sorbate. An increase in the initial metal concentration increases the biosorption capacity. The sorption data of investigated metal ion are fitted to Langmuir, Freundlich and Temkin isotherm models. The equilibrium data were well fitted by the Langmuir isotherm model (R2 ≥ 0.990). The maximum monolayer biosorption capacity of waste biomass YFW for Pb(II) ion, at 25.0 ± 0.5°C and pH 4.5, was found to be 19.23 mgg-1. This available waste biomass is efficient in the uptake of Pb(II) ions from aqueous solution and could be used as a low-cost and an alternative biosorbent for the treatment of wastewater streams bearing these metal ions

Fruit Wines Inhibitory Activity Against alpha-Glucosidase

Background: Fruit wines are well known for their profound health-promoting properties including both enzyme activations and inhibitions. They may act preventive in regard to diabetes melitus and other chronic diseases. Objectives: Potential alpha-glucosidase inhibitory activity of fruit wines made from blueberry, black chokeberry, blackberry, raspberry and sour cherry was the subject of this study. Method: In order to increase the alcohol content due to enriched extraction of total phenolics, sugar was added in the fruit pomace of the half of the examined fruit wine samples. Results: Compared with acarbose used as a positive control (IC50 = 73.78 mu g/mL), all fruit wine samples exhibited higher alpha-glucosidase inhibitory activity. Indeed, blueberry wine samples stood out, both prepared with IC50 = 24.14 mu g/mL, lyophilised extract yield 3.23% and without IC50 = 46.39 mu g/mL, lyophilised extract yield 2.89% and with addition of sugar before fermentation. Chlorogenic acid predominantly contributed to alpha-glucosidase inhibitory activity of the blueberry, black chokeberry and sour cherry wine samples. However, ellagic acid, a potent alpha-glucosidase inhibitor possessing a planar structure, only slightly affected the activity of the blueberry wine samples, due to the lower concentration. In addition to this, molecular docking study of chlorogenic acid pointed out the importance of binding energy (-8.5 kcal/mol) for the inhibition of the enzyme. Conclusion: In summary, fruit wines made from blueberry should be primarily taken into consideration as a medicinal food targeting diabetes mellitus type 2 in the early stage, if additional studies would confirm their therapeutic potential for the control of postprandial hyperglycemia

Effect of increased amounts of organic forms of selenium and vitamin E in fattening broilers on selected parameters of meat quality [Einfluss der Fütterung auf die Qualität von Broilern: Einfluss erhöhter Mengen an organischem Selen und Vitamin e in der B

The paper examined the effects of adding a meal of organic forms of selenium broilers on meat quality of broilers. The experiment was conducted on 150 poultry Hubbard provenance divided into 3 groups. Broilers were fed complete feed mixtures for fattening in broilers various standard and chemical composition. During the experiments the first O-I group of broilers was fed the mixture with added organic selenium in the amount of 0.3 ppm, the second O-II, received the food with the addition of 0.6 ppm, and the third experimental O-III with the addition of 0.9 ppm organic selenium. All groups were fed 100 IU receiving vitamin E. At the end of the experiment was carried slaughter broilers and sampling of 6 of carcass from each group as: white and dark meat, liver and heart for chemical analysis (content of selenium, vitamin E, protein, fat and fatty acids). At the end of the experiment was significantly greater (p lt 0.01) content of selenium in relation to other groups, the O-III group in the breast meat 0.61 mg/kg) in the drumstick (0.54 mg/kg) in liver (0.96 mg/kg) and heart (0.48 mg/kg). Content of vitamin E was significantly (p lt 0.01) higher in liver (4.49 mg/kg) O-II and O-III in relation to the O-I group. In experimental groups with increased content of selenium and 100 IU vitamin E was found significant (p lt 0.01) lower fat content (breast, heart), and higher protein content (p lt 0.01) in the liver. The total amount of saturated and polyunsaturated fatty acids several times was greater in the group with 0.9 mg/kg organic selenium in feed

Arsenic Removal from Water Using Industrial By-Products

In this study, removal of arsenic ions using two industrial by-products as adsorbents is represented. Removal of As(III) and As(V) from water was carried out with industrial by-products: residual from the groundwater treatment process, iron-manganese oxide coated sand (IMOCS), and blast furnace slag from steel production (BFS), both inexpensive and locally available. In addition, the BFS was modified in order to minimise its deteriorating impact on the initial water quality. Kinetic and equilibrium studies were carried out using batch and fixed-bed column adsorption techniques under the conditions that are likely to occur in real water treatment systems. To evaluate the application for real groundwater treatment, the capacities of the selected materials were further compared to those exhibited by commercial sorbents, which were examined under the same experimental conditions. IMOCS was found to be a good and inexpensive sorbent for arsenic, while BFS and modified slag showed the highest affinity towards arsenic. All examined waste materials exhibited better sorption performances for As(V). The maximum sorption capacity in the batch reactor was obtained for blast furnace slag, 4040 μgAs(V)/g

Acid and Temperature Treatments Result in Increased Germination of Seeds of Three Fescue Species

Efficient germination of fescue seeds is essential for successful establishment of meadows and pastures. This research was conducted to ascertain the effects of various acid and temperature treatments on seed germination in three fescue species: Festuca rubra, F (mina, and E pratensis. Seeds from different cultivars, populations, or lots were exposed either to four concentrations of sulfuric acid at three different time intervals (12 treatments) or six different temperatures at three different time intervals (18 treatments). Despite all belonging to the genus Festuca, the seed from different species responded differently to the treatments. The three optimum treatments for E rubra seed involved soaking in a 75% solution of sulfuric acid for 20 minutes (improved the germination rate by 19%), soaking in a 50% solution of sulfuric acid for 30 minutes (improved the germination rate by 18%) and exposure to either 60 degrees C or 70 degrees C for 90 minutes (improved the germination rate by 17%). For F. ovina seed, optimal treatments included soaking seeds for either 10 or 20 minutes in a 50% sulfuric acid solution (both treatments improved germination rates by 13%) or exposing seeds for 30 minutes in a 25% sulfuric acid solution and 80 degrees C for 60 minutes (improved germination rate by 12%). Two optimal treatments were identified for F. pratensis seed. Whereas the first involved soaking the seeds in a 75% sulfuric acid solution for 30 minutes (improved germination rates by 22%), the second involved either exposing the seeds to 90 degrees C for 90 or 60 minutes, or exposing the seeds to 80 degrees C for 90 minutes (improved germination rate by 21%). Our findings indicate that if fescue seed is to be sown during the autumn (two to three months after seed collecting), treating it with acid and temperature can significantly enhance its germination