Transfer Coefficient Research Articles

Electrochemical determination of glutathione in hemolysed erythrocytes

The physiological significance of determining glutathione (GSH) and its oxide form is obvious from their applications in clinical practices such as diagnostic experiments for diabetes, Parkinson’s disease, and cancers. Such an important detemination still needs the development of certain experimental procedures that are easy, fast, and cheap enough to implement. These procedural advantages can be provided through electrochemical methods. Therefore, in this study, at the surface of a glassy carbon electrode (GCE), a composite of functionalized multi-walled carbon nanotubes (MWCNTs) and formazon was used as a mediator to determine GSH electrochemically. The results indicated that this modified GCE is electrocatalytically very active for glutathione oxidation. Several techniques including cyclic voltammetry (CV), scanning electron microscopy (SEM), and differential pulse voltammetry (DPV) were used to characterize the electrode. Also, such kinetic parameters as the charge transfer rate constant and the transfer coefficient were calculated. In optimized conditions, there was a linear relationship between the DPV peak current of GSH oxidation and GSH concentration in the ranges of 1.0-100.0 and 100.0-800.0 µM at pH 7.0. As for the detection limit, it was found to be 0.73 µM.

Numerical Simulation of the Temperature Fields in a Single-Phase Flow in an Asymmetrically Heated Minichannel

The heat transfer in the single-phase flow of a liquid in an asymmetrically heated horizontal minichannel was investigated. Thermograms of the surface of a heater in the minichannel and the surface of its adiabatic part have been obtained with the use of an infrared camera, and they were used to construct temperature profi les for these surfaces. Stationary temperature distributions in the insulating foil, the heater surface, and the liquid fl ow in the minichannel have been obtained, respectively, with the use of the Laplace equation, the Poisson equation, and the energy equation involving the frictional heat losses. The solution of the system of these differential equations with special boundary conditions has culminated in the solution of three sequential inverse problems on the heat conduction in the indicated adjacent regions having different physical parameters. These problems were solved using the Trefftz method, and the temperature of the liquid flow in the minichannel was calculated by the Picard–Trefftz method. The temperature distributions obtained for the liquid flow and the heater surface were used to determine the heat transfer through the liquid–heater interface. The Trefftz and Picard–Trefftz methods yielded similar local heat transfer coeffi cients and temperature distributions.

Complex Modeling and Design of Catalytic Reactors Using Multiscale Approach—Part 1: Diffusion in Porous Catalyst

The presented work is dedicated to the modeling of catalytic reactors using a multiscale approach, based on the combination of cellular automata and Computational Fluid Dynamics (CFD). This work describes the first step in the development of a complex model of catalytic reactors and considers the diffusion of components inside a porous structure of an aluminosilicate catalyst. Various cellular automata were used to generate virtual porous structures of catalysts with specific surface areas equal to 250, 500, and 700 m2/g and to calculate the effective diffusion coefficient for the substance transfer inside the catalysts. The obtained effective diffusion coefficient was included in the CFD model of a laboratory scale reactor simulating extraction of aniline from the catalyst with methanol. Results of numerical experiments carried out using the CFD model were compared with the corresponding experimental data. It is shown that the proposed approach is suitable for describing macroscopic and microscopic mass transfer phenomena on consideration of the catalyst’s structure.

Frequency drift insensitive broadband wireless power transfer system

The resonant frequency of coils in a four-coil magnetic coupling resonance wireless power transfer (MCR-WPT) system has a direct impact on transfer coefficient. For efficient power transfer, most of the systems operate at high-Q resonant state, causing a narrow bandwidth and reducing the system tolerance to resonant frequency deviation. To deal with the problem, a four-coil MCR-WPT system characterized with broadband performance is investigated. Based on the equivalent circuit, the transfer coefficient and the input impedance are firstly calculated. The transfer characteristic at different resonant frequency under different transfer distances is discussed. By comparing the number and variance of the extreme values of transfer coefficient under different resonant frequencies, the resonant frequency for excellent broadband transmission is determined. To validate the broadband performance, frequency drift caused by capacitance variations is investigated at the resonant frequency of 19 MHz under the transfer distance of 45 mm. The results indicate that the MRC-WPT system generally maintains broadband transmission and the transfer coefficient at the excitation frequency of 19 MHz remains above 0.9 when the resonant frequency is deviated. Experiments have been performed to validate the excellent broadband performance. The results are generally consistent with the simulation analysis.

Electroreduction of Holmium Chloride in the Equimolar NaCl–KCl Melt

Rare-earth metals and their alloys are widely used in various engineering fields due to their unique physical and chemical properties. To prepare rare-earth-containing coatings, data on the kinetics of electrode processes with the participation of the rare-earth metals in salt molten media should be available. These problems are poorly understood for rare-earth metals. In the present study, the kinetic parameters of the cathode reduction (transfer coefficient, heterogeneous charge transfer rate constants) of holmium ions in the equimolar NaCl–KCl melt are determined in a temperature range of 1073–1173 K in a holmium chloride concentration range of 1–10 wt % using chronopotentiometry and chronovoltammetry. The dependences of the kinetic parameters on the temperature and concentration of rare-earth metal chloride are determined. The following reduction mechanism of complex ion in the aforementioned melts is suggested: $${\text{HoCl}}_{6}^{{3 - }}$$ = $${\text{HoCl}}_{4}^{ - }$$ + 2Cl–, $${\text{HoCl}}_{4}^{ - }$$ + e → $${\text{HoCl}}_{4}^{{2 - }}.$$

Portfolio turnover when IC is time-varying

We develop new formulas for the turnover and leverage of mean–variance optimal long–short market neutral portfolios, where active weights are obtained using a factor model conditional mean forecast and a conditional forecast error covariance matrix that reflects strategy risk. We show that for eight commonly used quantitative factors, the turnovers and leverages derived using our long–short formulas are quite close to what the practitioners actually implement. We further carry out extensive simulations for long-only active portfolios and develop a highly accurate empirical formula that relates long-only turnover to long–short turnover, a transfer coefficient, portfolio target tracking error, strategy risk and a benchmark choice coefficient. Our result shows that when the proper risk model is used in factor investing, the optimal portfolio’s turnover and leverage are well within reasonable practically implementable ranges even if no additional constraints are imposed.

Effect of Oxygen Content on Heat Transfer in Steam-Generating Tubes in Transverse Flow of Heavy Liquid-Metal Coolant

A series of works was conducted on determining the coefficient of heat transfer in a bundle of heat-exchange tubes in transverse flow of lead in the base oxygen regime and with oxygen concentration on the saturation line. The object of investigation was an experimental model consisting of a horizontal bundle of six rows of smooth tubes with four tubes per row. The investigation was conducted with sub- and supercritical pressure in the water loop. It was confirmed that the oxygen content in lead significantly affects the coefficient of heat transfer. In the experimental range of velocities up to 0.3 m/sec, the coefficients of heat transfer in the base oxygen regime are two to three times higher than for lead with oxygen concentration on the saturation line. In agreement with other studies, it was found that for lead with oxygen concentration on the saturation line the coefficient of heat transfer is velocity-independent in a narrow section.

Fabrication and Electrochemical Behavior Investigation of a Pt-Loaded Reduced Graphene Oxide Composite (Pt@rGO) as a High-Performance Cathode for Dye-Sensitized Solar Cells

A platinum-reduced graphene oxide thin film composite (Pt@rGO, 100 nm) was prepared on a fluorine-doped tin oxide- (FTO-) coated glass substrate by a screen printing method using a Pt@rGO screen printing paste (0.12% Pt;Pt/rGO=1.5 w/w). The as-prepared electrode (denoted as Pt@rGO/FTO) was used as the cathode for the assembly of dye-sensitized solar cells (DSSCs). It showed a well-dispersed and high loading of Pt on rGO surface with a particle size distributed around 10 nm. The redox behavior of ferrocene was performed at Pt/FTO, Pt@rGO/FTO, and rGO/FTO electrodes by a cyclic voltammetry (CV) method. The kinetic parameters, in particular, the standard reduction potential (E0, V), the transfer coefficient (α), the heterogeneous rate constant (k0, cm·s-1), and the diffusion coefficient (D, cm2s-1), were determined by CV data treatment using convolution-deconvolution and fitting methods. The values ofE0,α,k0, andDat Pt@rGO/FTO electrode were, respectively, 326 mV, 0.471, 3.33 cm·s-1, and 4.19 cm2·s-1, equivalent to those of Pt/FTO electrode (340 mV, 0.474, 3.18 cm·s-1, and 4.19 cm2·s-1). The Pt@rGO/FTO electrode exhibited excellent electrocatalytic activity compared to that of Pt thin film (Pt/FTO electrode) prepared from Pt commercial paste. The heterogeneous electron transfer rate constantk0(cm·s-1) for I3-/I-at Pt@rGO/FTO is 1.3 times faster than that at Pt/FTO. The energy conversion efficiency of the DSSCs assembled from Pt@rGO-DSSC cathode reached 7.0%, an increase of 20.7% over the commercial Pt-based cathode (Pt-DSSC, 5.8%). The rGO component in the Pt@rGO composite plays two important roles: (i) facilitating the electron transfer between Pt NPs catalyst and the FTO substrate via the bandgap effect and (ii) the enlargement catalytic surface area of Pt NPs via the loading effect. The rGO material has, therefore, potential to replace the Pt content and improve the performance of the DSSC device.

A glassy carbon electrode modified with carbon nanoonions for electrochemical determination of fentanyl.

Fentanyl is a pain reliever stronger and deadlier than heroin. This lethal drug has killed many people in different countries recently. Due to the importance of the diagnosis of this drug, a fentanyl electrochemical sensor is developed based on a glassy carbon electrode (GCE) modified with the carbon nanoonions (CNOs) in this study. Accordingly, the electrochemical studies indicated the sensor is capable of the voltammetric determination of traces of fentanyl at a working potential of 0.85 (vs. Ag/AgCl). To obtain the great efficiency of the sensor some experimental factors such as time, the potential of accumulation and pH value of the electrolyte were optimized. The results illustrated a reduction and two oxidation peaks for fentanyl in phosphate buffer (PB) with pH=7.0 under a probable mechanism of electrochemical-chemical-electrochemical (ECE). The differential pulse voltammetry (DPV) currents related to the fentanyl detection were linear with an increase of fentanyl concentrations in a linear range between 1μM to 60μM with a detection limit (LOD) of 300nM. Furthermore, the values of the diffusion coefficient (D), transfer coefficient (α) and catalytic constant rate (kcat) were calculated to be 2.76×10-6cm2s-1, 0.54 and 1.76×104M-1s-1, respectively. These satisfactory results may be attributed to utilizing the CNOs in the electrode modification process due to some of its admirable characterizations of this nanostructure including high surface area, excellent electrical conductivity and good electrocatalytic activity. Consequently, these finding points the achieving a simple sensing system to measure of the fentanyl as an important drug from the judicial perspective might be a dream coming true soon.

Collective effects in a dusty plasma with a magnetic field irradiated by hard radiation

The transfer coefficients of a rarefied low-temperature plasma (hereinafter referred to as LTP) with a condensed dispersed phase (hereinafter referred to as CDF) were calculated for characteristic temperatures T = 50 – 100 K in weak external magnetic fields (B = 10–6 – 1 Gauss). These effects of irradiation of LTP CDF plasma with X-ray and γ-ray fluxes, highenergy charged particles (electrons, positrons, protons and α-particles) are shown. For systems of positively charged monodisperse nanoparticles, new frequencies of collective MHD oscillations are determined. Significant physical differences between such interacting systems and their influence on the redistribution between the kinetic energy of particle flows and (also the energy of incident quanta of hard radiation) to magnetic and vice versa are shown. In this regard, the degree of dissipative scattering of energy entering the system is relevant for the interpretation of experimental spectroscopic data on scattering. The effects of such scattering are considered on specific examples. By its nature, the first type of scattering of the energy entering the physical systems under consideration consists in local energy losses due to pair interactions with atoms, molecules, and CDF of the medium. The second type of interactions considered is the scattering of charged particle flows and turbulent (like cyclonic vortices) LTP structures with CDF located in an external magnetic field. Comparison of these two mechanisms of dissipative losses shows their comparability.For the physical systems considered above, the transfer coefficients we are received. The relaxation times–τand gyrofrequencies– ω for a two-component electron gas during its interaction with CDF and ions of atoms and molecules in an external magnetic field are shown.For this multicomponent plasma, based on the Braginsky criteria (ωτ≫1, or ωτ≪1), for applying the previously obtained relations for the transfer coefficients between various plasma components are shown. It was found that the thermal, low-energy electronic component of the LTP is responsible for the recombination of atomic ions and the discharge of CDFs. The high-energy electrons Auger component leads to large temperature gradients and, as a consequence, significant heat fluxes. In turn, it has been shown that large temperature gradients cause significant currents of the charged component of NTP (electrons, atomic and molecular ions, CDF). It is shown that, in turn, the plasma generates local magnetic fields. The magnetic Reynolds number ea ≫ 1who was calculated in this work are shown that the plasma becomes turbulent. The main conclusion of the work is the proof that a charged monodisperse ultra-low density CDF in the field of hard radiation and an external magnetic field is almost always turbulent.

Study on non-stationary heat exchange in combined packages of water-resistant protective clothing of firefighters

The results of research of non-stationary heat exchange in combined packages intended for creation of special water- and heat-resistant protective clothing of firefighters from dangerous and harmful factors during emergency rescue and other urgent works, with participation of non-toxic substances, acid solutions, alkalis, oil and petroleum products, liquid toxic substances, as well as during operation in water with temperature from 0 to 70 °С are presented. The stability of clothing material packs has been investigated as a transient heat exchange process in a multilayer plate with ideal thermal contact at the joints of the layers. The unlimited plate is heated on both sides under different heat exchange conditions according to Newton’s Law, with constant action of the heat source on one of the surfaces of the hot liquid contacting through the waterproof thin surface. Second surface of the plate interacts with external medium, temperature of which varies according to linear law. At solving the equation of non-stationary thermal conductivity with nonlinear transport coefficients, linearization methods are used based on the approximation of nonlinear coefficients, such that nonlinear equations become approximately linear. The entire heat transfer process is divided into a plurality of small-time intervals within which the transfer coefficients are constant. The zonal method of investigation of non-stationary thermal conductivity in clothing packages establishes equations for calculation of temperature, densities of thermal flows, distribution of temperature across thickness of clothing packages. It has been shown that under accepted calculation simplifications, parameter values are well consistent with the experiment. The composition of the clothing package is proposed, which meets the technical requirements of TУ BY 101114857.082-2015 “Personal Protective Kits”.

On the extent of fracture toughness transfer from 1D/2D nanomodified epoxy matrices to glass fibre composites

In this study, the effects of adding nanofillers to an epoxy resin (EP) used as a matrix in glass fibre-reinforced plastic (GFRP) composites have been investigated. Both 1D and 2D nanofillers were used, specifically (1) carbon nanotubes (CNTs), (2) few-layer graphene nanoplatelets (GNPs), as well as hybrid combinations of (3) CNTs and boron nitride nanosheets, and (4) GNPs and boron nitride nanotubes (BNNTs). Tensile tests have shown improvements in the transverse stiffness normal to the fibre direction of up to about 25% for the GFRPs using the ‘EP + CNT’ and the ‘EP + BNNT + GNP’ matrices, compared to the composites with the unmodified epoxy (‘EP’). Mode I and mode II fracture toughness tests were conducted using double cantilever beam (DCB) and end-notched flexure (ENF) tests, respectively. In the quasi-static mode I tests, the values of the initiation interlaminar fracture toughness, G_{text{IC}}^{text{C}} , of the GFRP composites showed that the transfer of matrix toughness to the corresponding GFRP composite is greatest for the GFRP composite with the GNPs in the matrix. Here, a coefficient of toughness transfer (CTT), defined as the ratio of mode I initiation interlaminar toughness for the composite to the bulk polymer matrix toughness, of 0.68 was recorded. The highest absolute values of the mode I interlaminar fracture toughness at crack initiation were achieved for the GFRP composites with the epoxy matrix modified with the hybrid combinations of nanofillers. The highest value of the CTT during steady-state crack propagation was ~ 2 for all the different types of GFRPs. Fractographic analysis of the composite surfaces from the DCB and ENF specimens showed that failure was by a combination of cohesive (through the matrix) and interfacial (along the fibre/matrix interface) modes, depending on the type of nanofillers used.

Electrochemical Mechanism of Trivalent Chromium Reduction in ChCl-EG Deep Eutectic Solvents Containing Trivalent Chromium

In this work, the cyclic voltammetry (CV) was used to investigate the redox process of Cr(III) on glassy carbon electrode (GC) in deep eutectic solvents (DESs), prepared using choline chloride (ChCl) and ethylene glycol (EG). The anode and cathode branches of the CV curve meant the process of deposition/dissolution equilibrium of trivalent chromium. The equilibrium potential (Eeq) of Cr(III)/Cr(0) was −0.964 V (vs Ag QRE). The analysis of the potentiostatic current density transient (chronoamperometry (CA)) results showed that the electrodeposition process of Cr(III) involved multiple processes, mainly jad, j3D and jWR. By calculating the amount of charge (Qad%, Q3D%, and QWR%) in each process, it can be found that the contribution rate could be controlled by the potential to increase Q3D%. The kinetic parameters of Cr nucleation/growth rate were determined from the standard model of 3D nucleation of diffusion-control, such as nucleation rate (A), active centre number density (N0), and diffusion coefficient (D). The ln(A) and η were used to calculate the nucleated Gibbs free energy (Δ∼G(nc)), the critical core size (nc), the current exchange density (j0), the transfer coefficient (α), and the surface tension (σ). The chromium coating was constituted by particles of Cr(0), Cr2O3 and Cr(OH)3.

Translocation and accumulation of heavy metals in Ocimum basilicum L. plants grown in a mining-contaminated soil

The evaluation of the ecotoxicity effects of some heavy metals on the plant growth and metal accumulation in Ocimum basilicum L. cultivated on unpolluted and polluted soils represented the objective of the present study. The basil aromatic herb was evaluated in a laboratory experiment using soil contaminated with Cd, Co, Cr, Cu, Ni, Pb, and Zn, similar to the one from a mining area. The soils and different organs of the basil plants were analyzed, the total contents of the added elements being determined using inductively coupled plasma optical emission spectrometry. The ability of basil plants to accumulate metals from soil and to translocate them in their organs was evaluated by transfer coefficient, translocation factor, enrichment factor, and geo-accumulation index determinations. The basil plants grown in the metal-polluted soil showed stimulation effects comparing with the plants from the control soil. At the end of the exposure period, the plants had a visible increase of biomass and presented inflorescences and the leaves’ green pigment was intensified. The metals gathered differently in plant organs: Cd, Co, Cr, and Pb were accumulated in roots, while Cu, Ni, and Zn in flowers. Cr and Pb exceeded the toxic levels in roots. Also, the heavy metal intake depends on the plant development stages; thus, Cd, Cr, and Pb were accumulated more in mature plant leaves. The Cd and Pb contents were higher than the World Health Organization and European Commission permissible limits. The experimental results revealed that the basil plants exposed to a mixture of heavy metals have the potential to reduce the metal mobility from soil to plants. Translocation process from roots to flowers and to leaves was observed for Cu, Ni, and Zn, emphasizing a competition between metals. The calculated bioaccumulation factors were insignificant, but Cd and Pb concentrations exceeded the legal limits in the mature plants, being restricted for human or animal consumption.

Establishing material hygrothermal characteristics via long-term monitoring and best-fit numerical models

Numerical models of heat and moisture transfer for performance forecast of lightweight insulating assemblies require many inputs. These include exterior climate data (i.e. temperature, relative humidity, solar radiation), interior climate data or standard models, transfer coefficients, correct initial conditions, etc. Most importantly, one needs reliable material models. A material model includes porosity, density, heat capacity, but also non-constant properties, such as thermal conductivity, vapor/liquid water diffusivity, sorption curves. These are, in general, difficult to determine, and material database entries often are incomplete, or simply non-existent. However, if one performs long-term monitoring of temperature and relative humidity dynamics within building envelopes, there is a way to determine hygrothermal curves and properties of the underlying materials. This can be done by performing simulations and finding the set of optimal hygrothermal curves and coefficients such that the experimental data is matched sufficiently well. Despite the appeal, this best-fit model approach is fraught with perils due to many unknowns and must be used carefully. In this article, we demonstrate the application of this method to insulating assemblies for which 6+ years' worth of experimental data is available, and showcase our results obtained using WUFI Pro 6.3 and the derived and verified material models.

Experimental and numerical analysis of soil desiccating cracks in compacted and non-compacted specimens

This paper presents the results and analysis of two cracking tests carried on specimens of silty clay. One specimen was prepared in slurry conditions without applying energy and the other specimen was compacted. They were dried in an environmental chamber at a constant temperature and relative humidity to study the effect of the initial consistency on the cracking behaviour. Weight measurements and photographic images taken at regular intervals documented the evolution of the specimens. THM models were then carried to capture the unsaturated flow in the porous medium due to evaporation, and its resulting shrinkage. All the numerical analyses were coupled, incorporating the effect of porosity change on the balance equations and the constitutive model. The transfer coefficients in the imposed drying boundary condition were based on calculations of aerodynamic surface resistances, taking into consideration the new fronts for evaporation created by the cracks. The constructed numerical model results capture the gravimetric water content loss and the occurring shrinkage for both specimen conditions.

Computed tomography findings as determinants of pulmonary function tests in fibrotic interstitial lung diseases-Network-analyses and multivariate models.

The aim was to evaluate the impact of multiple high-resolution computed tomography (HRCT) features on pulmonary function test (PFT) biomarkers in fibrotic interstitial lung disease (FILD) patients. HRCT of subsequently ILD-board-discussed FILD patients were semi-quantitatively evaluated in a standardized approach: 18 distinct lung regions were scored for noduli, reticulation, honeycombing, consolidations, ground glass opacities (GGO), traction bronchiectasis (BRK) and emphysema. Total lung capacity (TLC), forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), FEV1/FVC, diffusion capacity for carbon monoxide (DLCO) and transfer coefficient (KCO) were assessed. Interactions between each PFT biomarker and all HRCT scores were visualized by network analyses, modeled according to the Schwarz Bayesian Information Criterion and incorporated in uni- and multivariate stepwise regression analyses. Among 108 FILD patients (mean age 67 years, 77% male), BRK extent was a major significant uni- or multivariate determinant of all PFT analyzed. Besides that, diffusion-based variables DLCO and KCO showed a larger dependency on reticulation, emphysema and GGO, while forced expiratory volume-based measures FEV1, FVC and FEV1/FVC were more closely associated with consolidations. For TLC, the only significant multivariate determinant was reticulation. In conclusion, PFT biomarkers derived from spirometry, body plethysmography and diffusion capacity in FILD patients are differentially influenced by semi-quantified HRCT findings.

Boiling Heat Transfer and Critical Heat Flux Enhancement Using Electrophoretic Deposition of SiO2 Nanofluid

The electrophoretic deposition (EPD) technique was used to create a uniform SiO2 thin film coating on boiling plates, 4 mm in width and 9 mm in length. Significant enhancement in critical heat flux (CHF), for the hydrophilic surfaces generated by this anodic EPD method, has been observed. In order to increase the coating strength, the plates were sintered at various temperatures. To find the thickness and uniformity of the coatings, the SEM images were captured. The captured images showed that the coating thickness uniformly increased up to 90 nm for 0.5% nanofluid percentage by the EPD method. The results show that the hydrophilic and super-hydrophilic surfaces have different boiling heat transfer (BHT) coefficients and CHF behaviors. Also, the results showed an increase of 160% in the CHF value by sintering compared to a bare surface. However, because of the setup simplicity, the shape independency, the particle-coating uniformity, and thickness controllability, the EPD technique can be an appropriate option for modification of the surface and coating on the nuclear fuel cladding.

Моделювання системи керування з регулятором на підставі внутрішньої моделі

Засобами імітаційного моделювання проаналізовано функціонування замкнутих систем керування в умовах зміни властивостей інерційного об'єкта керування. Порівняли роботу таких систем: одноконтурної з ПІД регулятором, багатоконтурних з ПІ-ПД керуванням та систем із зовнішнім регулятором на підставі внутрішньої моделі. Серед систем керування із внутрішньою моделлю одна побудована на підставі моделі об'єкта керування. Ми запропонували іншу система, в якій структура зовнішнього регулятора реалізована на базі внутрішньої моделі замкнутого внутрішнього контуру з ПД регулятором. Для спрощення процедури налаштування зовнішнього регулятора вибрано наближену модель об'єкта керування у вигляді послідовно з'єднаних аперіодичної ланки першого порядку та ланки запізнення. Знайдено наближену внутрішню модель зустрічного паралельного з'єднання об'єкта керування та ПД регулятора та отримано наближену обернену модель. Встановлено, що в умовах зміни властивостей об'єкта керування запропонована система зберігає достатній запас стійкості і порівняно з іншими досліджуваними системами має переваги. Так, зі збільшенням коефіцієнта передачі об'єкта керування у 2 рази та збільшенням інерційності на 30 % перехідні процеси каналом заданого значення мають найменший час регулювання. Окрім цього, каналом збурення така система забезпечує найменше динамічне відхилення для всіх варіантів дослідження.

Kinetics of active zinc dissolution in concentrated KOH solutions

The kinetics of zinc dissolution in concentrated potassium hydroxide solution were determined as a function of KOH concentration, amount of added ZnO, and temperature through linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The measurements were evaluated with a simplified reaction scheme in which an intermediate ZnI species is formed on the electrode surface that subsequently reacts to a soluble ZnII species. Analysis of the LSV data with a two-step Butler–Volmer kinetics showed that the transfer coefficients and the surface coverage of the intermediate are approximately constant in the entire range of operation conditions, whereas the exchange current density for the first reaction step is about five times larger than for the second step. Analysis of the dynamic EIS measurements resulted in very similar current densities than obtained from the quasi-stationary LSV method. For the first time, activation energies describing the temperature dependence of the exchange current density were also determined.