Modification of the Dynamics Characteristics using a Reanalysis Procedures Technique

The present paper deals with the problem of dynamic improving characteristics for a sub-structure (bucket wheel excavator) of a complex mining structure. The procedure used in this paper is concerned with the analysis of the distribution of potential and kinetic energy in every element of structure, which gives prediction for which elements need reanalysis. Reanalysis technique can be done for the structure using finite element methods. Therefore, some information like material, size, and boundary conditions should be prepared before FE model is constructed. Because the optimum structure design has high natural frequency, the main aim of dynamic modification is to increase natural frequencies and to increase the difference between them

Universal modular device for electrochemical syntesis of the disinficant

For the water disinfections practically four different technologies (chlorine, ozone, hypochlorite, chlorine dioxide) are used nowadays in the world. The oldest and the most exploited one, so called conventional, is the disinfections with gaseous or liquid chlorine. The biggest producers of the equipment for the water treatment in the world mainly possess all mentioned technologies for water disinfections. It is easy to concluded that the technology of water disinfections with the hypochlorite solution produced by the electrolysis of 3% solution of sodium chloride on the site of water chlorination is not only the most convenient from the point of economical aspects, but also from the point of the ecological aspect

Kinetics of the electrolytic hydrogenation of glucose

U doktorskoj disertaciji je proučavana kinetika i mehanizmi paralelnih reakcija izdvajanja vodonika i redukcije glukoze na elektrodi od amalgamisanog cinka u neutralnim i slaboalkalnim rastvorima Na2SO4, pri različitim koncentracijama glukoze. Na osnovu eksperimentalnih i simuliranih podataka mogu se izvesti sledeći zaključci o kinetici reakcija izdvajanja vodonika i elektrohemijske redukcije glukoze: U prisustvu i odsustvu glukoze u rastvoru, reakcija izdvajanja vodonika se odigrava preko dva paralelna mehanizma . Prema prvom mehanizmu , reakcija se odigrava preko tri konsekutivna elementarna stupnja a heterogeni hemijski stupanj kontroliše ukupnu brzinu reakcije. Navedeni mehanizam je dominantan u oblasti potencijala od potencijala otvorenog kola pa do potencijala gde se javlja granična struja. Aktivna mesta za reakciju izdvajanja vodonika u predloženom mehanizmu su površinski oksidi metala. Granična struja je heterogena reakciona granična struja. Na negativnijim potencijalima reakcija izdvajanja vodonika se dominantno odigrava na metalnoj površini preko Folmer-Heirovski reakcionog puta u kome Folmerov stupanj kontroliše ukupnu brzinu reakcije, pri veoma malim stepenima pokrivenosti sa Hads reakcionim intermedijerom. Elektrokatalitička hidrogenacija glukoze se odigrava u oblasti potencijala gde se jednovremeno odigrava reakcija izdvajanja vodonika dominantno prema prvom predloženom mehanizmu. Heterogeni hemijski stupanj u mehanizmu izdvajanja vodonika je . u kompeticiji sa elementarnim stupnjem hemijske katalitičke hidrogenacije glukoze u kome se odigrava reakcija između adsorbovanog vodonika i adsorbovanih molekula glukoze na površini katalizatora. Predložen je kinetički model koji dobro fituje krive polarizacije i spektre impedancije. Model sadrži jednačine za brzinu svih elementarnih stupnjeva sa odgovarajućim vrednostima konstanti brzina, kao i Lengmirove adsorpcione izoterme za vodonik i glukozu. Kinetički model izuzetno dobro fituje eksperimentalno određene vrednosti za brzinu dobijanja sorbitola u zavisnosti od koncentracije glukoze, gustine struje i temperature i u tom smislu predstavlja značajno poboljšanje postojećih poluempirijskih jednačina za brzinu koje nisu mogle uzeti u obzir uticaj sporednih reakcija na iskorišćenje struje. Ograničenja koja imaju empirijski pristup su prevaziđena u predloženom kinetičkom modelu uključivanjem odvojenih izraza za brzine reakcije elektrohemijske redukcije glukoze i izdvajanja vodonika. U radu su takođe napravljena značajna poboljšanja postojećih karakteristika elektrokatalizatora, što otvara realnu mogućnost primene amalgamisanog cinka kao elektrodnog materijala za industrijsku proizvodnju sorbitola elektrokatalitičkom hidrogenacijom D-glukoze.In this PhD Thesis, the kinetics and mechanism of the hydrogen evolution reaction and glucose reduction to sorbitol were studied on amalgamated zinc electrode in neutral and slightly alkaline solutions of Na2SO4 with various concentration of glucose. On the base of all the experimental and calculated data the following information concerning the kinetics of hydrogen evolution and glucose reduction can be summarized: • In both the presence and absence of glucose, hydrogen evolution reaction proceeds via two parallel mechanisms. The first mechanism is considered to be the consecutive combination of the three steps with the heterogeneous chemical step as the rate controlling one. This mechanism is dominant in the potential range from the open circuit potential (OCP) up to the potentials where limiting current appears. The active sites for hydrogen evolution reaction in the proposed mechanism are surface oxides. The limiting current is a heterogeneous reaction limiting current. • At very high negative potentials the hydrogen evolution takes place dominantly on a metallic surface through the Volmer-Heyrovsky route with the Volmer step being rate controlling one and at a very low surface coverage with Hads. • Electrocatalytic hydrogenation of glucose takes place in the potential range where the first mechanism for hydrogen evolution is operable the heterogeneous chemical step for the hydrogen evolution occurs in conjuction with the chemical catalytic hydrogenation of glucose. • A kinetic model for the prediction of polarization curves and impedance spectra was formulated. The model contains rate equations for the individual reaction steps, a Langmuir adsorption isoterms for hydrogen and glucose. Theoretical current density - potential predictions were in excellent agreement with the data obtained from polarization experiments. • The kinetic model accurately predicted experimental sorbitol production rates , in this regard, in a significant improvement over semiempirical rate equations which cannot account for current efficiency losses by an unwanted side reaction. • The limitation of the empirical approach was overcome in the present theory by including separate rate expressions for glucose reduction and hydrogen evolution reaction. • The significant improvement of electrocatalyst design was made, which makes possibility of its application in the industrial production of sorbitol by electrolytic hydrogenation of D-glucose

Formation of the separation layer in the production of tools by electroforming

U ovom raduje optimizovana tehnika dobijanja razdelnog sloja u procesu dobijanja alata za oblikovanje plastičnih masa postupkom elektroformiranja. Cilj je bio da se dobije što tanji sloja koji najmanje utiče na tačnost reprodukovane kopije. Ispitane su dve tehnike dobijanja razdelnog sloja i to: hemijska pasivacija u 2% bihromatu i nanošenje koloidnog sloja u 5% rastvoru albumina u etanolu. Dobijeni su zadovoljavajući rezultati, jer su dobijene kopije sa tačnošću od oko 50 nm u odnosu na model na kome se obavlja taloženje.The procedure for the formation of the separation layer in the production of tools by electroforming is optimized. The goal was to make very thin layer in order to achieve high precision in reproducing of the model. Two techniques for preparation of the separation layer were investigated chemical passivation in 2% bichromate solution and deposition of the colloid layer in 5% solution of albumin in ethanol. The precision of the copies obtained in this work was about 50 nm, what is considered to be acceptable

Formation of the separation layer in the production of tools by electroforming

U ovom raduje optimizovana tehnika dobijanja razdelnog sloja u procesu dobijanja alata za oblikovanje plastičnih masa postupkom elektroformiranja. Cilj je bio da se dobije što tanji sloja koji najmanje utiče na tačnost reprodukovane kopije. Ispitane su dve tehnike dobijanja razdelnog sloja i to: hemijska pasivacija u 2% bihromatu i nanošenje koloidnog sloja u 5% rastvoru albumina u etanolu. Dobijeni su zadovoljavajući rezultati, jer su dobijene kopije sa tačnošću od oko 50 nm u odnosu na model na kome se obavlja taloženje.The procedure for the formation of the separation layer in the production of tools by electroforming is optimized. The goal was to make very thin layer in order to achieve high precision in reproducing of the model. Two techniques for preparation of the separation layer were investigated chemical passivation in 2% bichromate solution and deposition of the colloid layer in 5% solution of albumin in ethanol. The precision of the copies obtained in this work was about 50 nm, what is considered to be acceptable

Morphological, microstructural and magnetic characteristics of electrodeposited Ni-Fe-WCu alloy powders

Nanostructured Ni-Fe-W-Cu alloy powders were electrodeposited from an alkaline ammonium citrate solution on a titanium cathode. Powder particles were dendrite- and cauliflower-shaped. The dendritic particles had a high density of branches made up of interconnected globules. XRD analysis showed that the powder contained an amorphous matrix and FCC nanocrystals of the solid solution of Fe, W and Cu in Ni. As the deposition current density increased, the mean nanocrystal size decreased, and the mean value of internal microstrain and the total weight percent of Fe and Ni in the alloy increased. The powders deposited at higher current densities exhibited higher magnetization. During annealing at temperatures up to 460°C, the powders underwent short-range ordering, which caused an increase in magnetization, whereas at temperatures above 460°C, the magnetization decreased due to the formation of large FCC crystalline grains

SISTEM ZA PREČIŠĆAVANJE PIJAĆE VODE SA POVEĆANOM TVRDOĆOM I KONCENTRACIJOM AMONIJAKA, GVOŽĐA, MANGANA

Water is one of the most important universal solvents for gerat number of substances. Despite the fact that it is found in nature in huge quantities, there is almost no completely clean water in nature. The purest water in the nature is in glaciers, snow and possibly rainwater, although this water contains also a certain amount of impurities. Water in natural springs (underground and surface springs) is more or less loaded with minerals that can be non-toxic or very toxic. In order to use it as drinking water, it is necessary that such water (chemically and bacteriologically) be in accordance with the standards and Guidance which defines the maximum allowed concentrations of certain mineral compounds and bacteria in drinking water.Publishe

Innovative system for electrochemical active chlorine production in coaxial and cabinet-type reactors, International scientific and professional conference

Drinking water, whether previously purified or not, even if entirely clear, can often be contaminated with bacteria, viruses, or harmful microbes, necessitating disinfection. Disinfection serves as the final and sometimes the sole process in preparing drinking water. This paper presents a solution for the on-demand production of active chlorine (sodium hypochlorite) without the need for storage, aiming to prevent its degradation and ensure the safety of workers during handling

Razvoj titanskih RuO2/TiO2 anoda i uređaja za in situ proizvodnju aktivnog hlora

Chlorine is used worldwide for water disinfection purposes. However, due to its toxicity the EU has imposed a set of standards that must be applied when transporting and storing chlorine. In Serbia, numerous studies have been conducted attempting to develop the technology for the generation of active chlorine disinfectant but with a non-toxic aqueous solution of sodium chloride as the raw material. This study provides an overview of the titanium anodes activated by thermally obtained solid solution of ruthenium and titanium oxide development. It also presents new findings on the effect of the temperature of thermal treatment, the composition, the thickness of an active coating on its microstructural properties, and consequently on the catalytic activity, ion selectivity, and corrosion stability during active chlorine generation through the electrolysis of dilute sodium chloride solutions at room temperature. The study also evaluates the effect of the kinetic and operational parameters of the electrochemical process of active chlorine generation on both current and energy efficiencies. The results obtained were used to determine optimal values of technological parameters of the production process. This comprehensive research resulted in the construction of different types of remote-controlled and fully automated active chlorine generating plants.U radu je dat pregled razvoja aktivnih titanskih anoda za reakciju oksidacije hloridnih jona u istraživačkim laboratorijama u Srbiji. Prikazani su i novi rezultati istraživanja efekta temperature termičke obrade, sastava i debljine aktivne RuO2/TiO2 prevlake na titanu na njena mikrostrukturna svojstva i odraz ovih svojstava na katalitičku aktivnost, jonselektivnost i korozionu stabilnost u procesu dobijanja aktivnog hlora. Ustanovljen je i efekat kinetičkih i operativnih parametara procesa elektrolize razblaženih rastvora natrijum-hlorida na iskorišćenje struje i energije po aktivnom hloru. Na osnovu ovih ispitivanja konstruisana je ćelija za elektrolizu i utvrđene su optimalne vrednosti tehnoloških parametara procesa proizvodnje aktivnog hlora. Sveobuhvatna istraživanja rezultirala su konstrukcijom različitih tipova postrojenja za in situ proizvodnju aktivnog hlora

Characteristics of the citrate-based zinc-polyaniline secondary cell with supercapattery behavior

The electrochemical characteristics of zinc–polyaniline (PANI) secondary cell in the electrolyte containing 0.8 M Na citrate, 0.3 M NH4Cl and 0.3 M ZnCl2 is investigated. Based on the measurements of potentials and voltage of the cell during charge/discharge for the currents in the range of 18 to 45 mA, the specific electrode capacity of 85 to 55 mA h g-1, the specific energy of 60–40 mW h g-1 and the specific power of 150–350 mW g-1, is determined. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON172046: Electrochemical synthesis and characterization of nanostructured functional materials for applications in new technologies