Comparative review of the sequential analysis and other models for evaluating school classes

U ovom radu imamo za cilj da uporedimo i prikažemo prednosti postupka sekvencijalne analize (Ivić, Pešikan, Antić 2001) u odnosu na druge iz literature poznate instrumente za psihološko-didaktičku analizu časa. U instrumente sa kojima poredimo sekvencijalnu analizu uvrstili smo sledeće: Flanders Interaction Analysis Categories (Flanders 1970), Mesner-Fuglisterova skala (Mesner, Fuglister 1973), ETH Wiss - 92 instrument (Educational Development and Technology, 2007) i CLASS sistem (Pianta, La Paro, Hamre 2007). Rad se sastoji iz dva dela. U prvom delu rada predstavljamo odabrane instrumente, dok u drugom delu ove instrumente poredimo na osnovu četiri kriterijuma - odnos između instrumenta kao istraživačke tehnike i nastave kao predmeta analize, priroda jedinice za analizu školskog časa, sadržaj jedinice za analizu školskog časa, postupak globalne procene časa.The goal of this paper is to highlight the advantages of the sequential analysis (Ivić, Pešikan, Antić 2001) compared to other existing instruments for psychological-didactical analysis of school classes-Flanders' Interaction Analysis Categories (Flanders 1970), Füglister-Messner scale (Füglister, Messner 1973), ETH Wiss-92 instrument (Educational Development and Technology 2007) and CLASS system (Pianta, La Paro, Hamre 2007). The paper consists of two parts. In the first part the aforementioned methods are presented, while in the second these methods are compared on the basis of four criteria-the relationship between the instrument as a research technique and teaching as the object of the analysis; the nature of the smallest element of a school class analysis; the content of the smallest element of a school class; the procedure of the global evaluation of a class. The conducted analyses allow us to put the sequential analysis on one side and the other evaluative instruments on the other, as two different categories of evaluative instruments. The sequential analysis is in both technical and practical sense conceived in such a way that preserves the psychological essence of teaching as a process based on interaction. On the other side, the other instruments represent analytical procedures that reduce psychological and didactic value of the evaluation of a class. Therefore these instruments and their results do not have sufficient theoretical and practical value when it comes to psychological-didactical evaluation of school classes

Formation of niobium oxides by electrolysis from acidic aqueous solutions on glassy carbon

In this study niobium oxide films were formed without peroxo-precursors from three different mixed acidic aqueous solutions on glassy carbon. Linear sweep voltammetry and potential step were techniques used for electrochemical experiments. The simultaneous and consecutive electrochemical reduction of water, nitrate and sulphate ions provided an alkaline environment with oxygen in the near vicinity of the working cathode, which in combination with the present niobium ions, produced niobium oxides and/or oxyhydroxides on the glassy carbon substrate. The formed deposits were analyzed using scanning electron microscopy and energy dispersive spectroscopy and appear to consist of NbO, NbO2 and Nb2O5. Both the niobium and acid concentration of the electrolytes used influenced the morphology and particle size of the deposits. The formation of niobium-fluoride and hydrogen-niobiumoxide complexes is addressed

Morphology of aluminium electrodeposited on aluminium from AlCl3+urea solvate ionic liquid

The ionic liquid, made of urea and AlCl3, known as deep eutectic solvent (DESs) has already shown to be low‐cost electrolyte suitable for aluminum electrodeposition. By applying appropriate potentiostatic or galvanostatic electrolysis regime, aluminium is successfully electrodeposited from the deep eutectic solvent onto aluminium substrate at nearly room temperatures. Morphologies of the produced deposits were characterized by scanning electron microscopy (SEM) and chemical composition by energy-dispersive X-ray (EDX) analysis. The electrodeposited aluminium displayed different morphology depending on the deposition conditions applied

Electrochemical Deposition of Aluminium on Aluminium from Ureabased Electrolyte

Electrochemical deposition/dissolution of aluminium to/from aluminium in deep eutectic solvent (DES), made of the AlCl3+urea, at temperatures of 25 to 60°C have been investigated. The depositions were performed in potentiostatic modes. The morphology of the obtained deposits was characterized using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Critical overpotential of aluminium deposition increased from around – 0.120 V at 25°C to around – 0.050 V at 50°C. All recorded currents were generally speaking small, but would substantially increase with increasing working temperature (from 0.01 mA cm-2 up to 0.25 mA cm-2). Current/time transients recorded at overpotentials over – 0.100 V vs. Al indicate continuous three-dimensional nucleation and growth. Epitaxial growth over aluminium substrate was not observed under applied experimental conditions. Electrodeposition/dissolution processes of aluminium under chosen conditions were reversible, reproducible and slow (relatively small current densities, bellow 0.3 mA cm-2). Polarization curves recorded noticeable dependence of aluminium deposition/dissolution reversible potential on temperature applied. The deposits obtained showed variety of morphological shapes (needles, rods, flakes, Fig.1) depending on the working temperature and potential applied. All the deposits were made of crystallites grouped randomly into more or less separate agglomerates which were positioned over lower layer of densely populated much smaller crystallites. Lower layer showed good adherence to the substrate and exhibited high surface area. Density of the crystallites distribution over the substrate and complicity of the crystal forms increased with the potentials applied

Electrochemical investigation of 2-thiohydantoin derivatives as corrosion inhibitors for mild steel in acidic medium

Four 2-thiohydantoin derivatives were synthesized and their corrosion inhibition properties on mild steel (MS) in 0.5M HCl solution was evaluated using usual gravimetric and electrochemical methods (weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS). Morphology of the metal surface was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The study has shown that these compounds provide good protection for mild steel against corrosion in the acidic medium

Electrochemical study of Nd and Pr co-deposition onto Mo and W from molten oxyfluorides

Electrodeposition processes of neodymium and praseodymium in molten NdF3 + PrF3 + LiF + 1 wt.%Pr6O11 + 1 wt.%Nd2O3 and NdF3 + PrF3 + LiF + 2 wt.%Pr6O11 + 2 wt.%Nd2O3 electrolytes at 1323 K were investigated. Cyclic voltammetry, square wave voltammetry, and open circuit potentiometry were applied to study the electrochemical reduction of Nd(III) and Pr(III) ions on Mo and W cathodes. It was established that a critical condition for Nd and Pr co-deposition in oxyfluoride electrolytes was a constant praseodymium deposition overpotential of ≈−0.100 V, which was shown to result in co-deposition current densities approaching 6 mAcm−2 . Analysis of the results obtained by applied electrochemical techniques showed that praseodymium deposition proceeds as a one-step process involving exchange of three electrons (Pr(III)→Pr(0)) and that neodymium deposition is a two-step process: the first involves one electron exchange (Nd(III)→Nd(II)), and the second involves an exchange of two electrons (Nd(II)→Nd(0)). X-ray diffraction analyses confirmed the formation of metallic Nd and Pr on the working substrate. Keeping the anodic potential to the glassy carbon working anode low results in very low levels of carbon oxides, fluorine and fluorocarbon gas emissions, which should qualify the studied system as an environmentally friendly option for rare earth metal deposition. The newly reported data for Nd and Pr metals co-deposition provide valuable information for the recycling of neodymium-iron-boron magnets

Electrodeposition of Nb and Al from chloroaluminate melt on vitreous carbon

Niobium and aluminium were electrodeposited at 200 °C under argon atmosphere onto vitreous carbon from inorganic chloroaluminate melts (AlCl3+NaCl) with added niobium. Niobium was introduced into the electrolyte by anodic dissolution of metallic niobium or by chemical dissolution of Nb2O5 in a melt of equimolar AlCl3+NaCl mixture. The processes of deposition/dissolution onto/from vitreous carbon were investigated by cyclic voltammetry and chronoamperometry. Characterization of the obtained deposits was done by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The only observed reduction processes on the working electrode in the potential window from 1.000 V to – 1.000 V vs. Al, were individual niobium deposition and codeposition of niobium and aluminium with Al-Nb alloys formation. Electrodeposition of niobium from the chloroaluminate melt with added niobium (V) oxide seems to start at around – 0.100 V vs. Al and at about – 0.200 V vs. Al aluminium starts codepositing. During the codeposition Nb-Al alloys were formed. Niobium deposition starting potential from the electrolyte with niobium added by anodic dissolution starts at 0.100 V vs. Al, and aluminium codeposition starting potential was at around – 0.025 V vs. Al, followed by Nb/Al alloy formation

Elektrohemijsko taloženje Nd i Pr na W iz fluoridnih rastopa

Electrodeposition of neodymium and praseodymium metal from molten NdF3+PrF3+LiF+ 0.5wt.%Pr6O11+0.5wt.%Nd2O3 electrolytes on W was investigated using voltammetry at 1050 °C. The square wave voltammetry confirmed that Nd electrodeposition is a two-step reduction process: first, involving one electron exchange (Nd(III)→Nd(II)) and second, involving two electrons exchange (Nd(II)→Nd(0)). However, praseodymium deposition proceeds as an one-step process involving exchange of three electrons (Pr(III)→Pr(0)). Nd and Pr metals were electrodeposited applying potentiostatic mode. The working electrode surface was analyzed by X-ray diffraction after Nd and Pr co-deposition.Elektrohemijsko taloženje neodijuma i prazeodijuma iz fluoridnog NdF3+PrF3+LiF+ 0.5wt.%Pr6O11+0.5wt.%Nd2O3 rastopa na W radnoj elektrodi ispitivano je pomoću voltametrijskih tehnika na 1050 °C. Voltametrija sa pravougaonim talasima (SWV, square wave voltammetry) potvrdila je da je elektrohemijsko taloženje Nd proces koji se odvija u dva koraka: prvi, uključuje razmenu od jednog elektrona (Nd(III) → Nd(II)) i drugi korak, uključuje razmenu dva elektrona (Nd(II) → Nd(0)). Međutim, taloženje prazeodijuma uključuje izmenu tri elektrona (Pr(III) → Pr(0)) u jednom koraku. Nd i Pr su elektrohemijski taloženi primenom potenciostatskog režima. Nakon elektrohemijskog taloženja Nd i Pr površina radne elektrode analizirana je rengensko-difrakcionom tehnikom.XII YuCorr International Conference, September 13-16, 2021, Tara Mountain, Serbia, http://sitzam.org.rs/YUCORR

Electrochemical deposition of neodymium and praseodymium on molybdenum from molten fluoride

Neodymium and praseodymium were electrochemically co-deposited onto Mo cathode applying constant potential, from fluoride-based molten salts containing the corresponding rare earth oxides. According to the recorded voltammograms, it appears that in the investigated system, the electrodeposition of neodymium proceeds as a two-step reduction process: Nd(III)→Nd(II) and Nd(II)→Nd(0), whilst the praseodymium deposition proceeds as an one-step reduction process: Pr(III)→Pr(0). However, it was also recognized that at the same time a substantial amount of NdF2 was formed as a result of the disproportionation reaction between the electrodeposited Nd metal and Nd(III) present in the electrolyte. The deposit on the working electrode surface was recorded by optical microscopy and analyzed by X-ray diffraction (XRD). The analysis made upon the applying the potentiostatic deposition regimehas shown Nd/Pr metals present on the molybdenum cathode

Influence of Rare Earth Oxide Concentration on Electrochemical Co-Deposition of Nd and Pr from NdF3-PrF3-LiF Based Melts

The impact of rare earth oxide (REO) concentration on the deposition process and selective recovery of the metal being deposited from a molten fluoride salt system was investigated by applying deposition of Nd and Pr and varying the concentration of REO added to the electrolyte. A ternary phase diagram for the liquidus temperature of the NdF3-PrF3-LiF system was constructed to better predict the optimal electrolyte constitution. Cyclic voltammetry was used to record three redox signals, reflecting the processes involving Nd(III)/Nd and Pr(III)/Pr transformations. A two-step red/ox process for Nd(III) ions and a single-step red/ox process for Pr(III) ions were confirmed by square-wave voltammetry. The cyclic voltammetry results indicated the possibility of neodymium and praseodymium co-deposition. In order to sustain higher co-deposition rates on the cathode and to avoid increased production of PFC greenhouse gases on the anode, a low-overpotential deposition technique was used for Nd and Pr electrodeposition from the electrolyte with varying Nd2O3 and Pr6O11 concentrations. Co-deposited neodymium and praseodymium metals were characterized by electron probe microanalysis (EPMA) and X-ray diffraction (XRD) analysis. After electrodeposition, concentration profiles of neodymium and praseodymium were recorded, starting from the cathode surface towards the electrolyte bulk. The working temperature of 1050 °C of the molten fluoride salt basic electrolyte, in line with the constructed phase diagram, was validated by improved co-deposition and led to a more effective deposition process