REGRESSION EQUATION FOR THE ELECTRODEPOSITION PROCESS OF FeS THIN FILMS

Antimony selenide (Sb2Se3), is an excellent photovoltaic absorber due to its high absorption coefficient (> 105 cm–1) at the visible region and 1.17 eV band gap. In recent years, the power conversion efficiency of Sb2Se3 thin film solar cells has gradually enhanced. Therefore, given the great interest in this material, this work is devoted to the study of a mathematical model for the optimization of the preparation of thin Sb–Se films by the electrochemical method. The study was conducted by potentiodynamic, potentiostatic and galvanostatic methods carried out under different conditions at Pt, Cu and Ni elec-trodes. The kinetics and mechanism of the electroreduction of antimony and selenite ions in the tartaric acid were studied separately for the electrochemical deposition. On the basis of cyclic polarization, X-ray phase and SEM-EDX analyses, it is found that Sb–Se thin films are deposited on Pt and Ni electrodes, but not on Cu electrode. The mathematical calculations were performed in the OptimME software package using specially developed software for this process. By studying the effects of various factors (concentration of the initial components, temperature, current density, etc.), the optimal electrolysis mode and electrolyte composition for the co-deposition process were selected. Based on these results, Student and Fisher criteria were assigned for future purposes and regression coefficients were estimated. The obtained regression equation determines the electrolyte content and the electrolysis conditions, which allows precipitating the Sb–Se alloy containing the required amount of Sb. Calculations and experimental results show that the error of the regression equation for obtaining the Sb–Se alloy is =6.4%.

The paper reports the results of mathematical modeling and optimization of the process of obtaining thin films based on Mo-Re alloy by electrodeposition. The study of electrodeposition of Mo-Re alloys was carried out using methods of potentiodynamic, galvanostatic, and cyclic voltammetry under different conditions on a Pt electrode. Studies have been conducted using the method of planning experiments and a regression equation is obtained. Based on the experimental data, the obtained regression equation was analyzed, the Fisher criterion was calculated and the significance of the regression coefficients was estimated. To confirm the experimental results, based on the data obtained, the coefficients of the regression equation were refined, and the criteria of significance and adequacy were calculated. The calculations based on the experimental data indicate that the regression equation adequately describes the process of co-deposition of rhenium with molybdenum.


 
 The analysis of the operating conditions of a typical district heating system, in particular, a hot water gas boiler, was carried out. It is shown that the boiler, as the main control object, operates under conditions of constant change in external heat load, which, due to their random nature, leads to a number of uncertainties. The expediency of the mathematical description of uncertainties using the stochastic method as the most tested in practical conditions is substantiated. According to the results of the passive experiment on the hot water gas boiler KVG6.5-150 of the district heating system of one of the districts of Kharkov, an array of hourly experimental data was obtained, reflecting the main performance indicators of the hot water boiler. As a result of data processing by the least squares method, a mathematical model of the boiler was obtained in the form of a linear regression equation, reflecting the relationship between the temperature of the coolant at the boiler outlet and the ambient air temperature, the temperature of the coolant at the inlet to the boiler and with the flow rates of natural gas and coolant to the boiler. The obtained regression equation was verified by Student's t-test, which confirmed the significance of all coefficients of the regression model. The practical significance of the multiple regression equation was assessed using the coefficient of determination. The quality of the multiple regression equation as a whole was assessed using Fisher's F-test. Since parallel surveys were not conducted, instead of checking the adequacy, the quality of the approximation of the experimental points by the accepted regression equation was assessed, that is, it was checked whether this equation makes sense. Such a test was carried out by comparing the residual variance and the variance relative to the mean. The calculation results showed that the value of the coefficient of determination significantly exceeds the allowable value, and the actual value of the Fisher criterion significantly exceeds the table value. The obtained indicators led to the conclusion that the relationship between the variables in the regression model is significant, and the proposed stochastic method and the multiple linear regression equation can be used to make decisions in the process of synthesizing the technical structure of a computer-integrated control system for objects of a district heating system.
 
 
 
 
 

The importance of this research links to the controversial discussion about the role of the value-added tax (VAT) in the sphere of macroeconomic regulation. The assumption of its neutral influence on economic growth has led to increasing VAT rate in Russia from 18% to 20%. However, the reduction of consumer expenditures, revenues, and profits is a possible negative effect. In addition, people criticize the mechanism of VAT refund for the absence of any impact on export and investment. Thus, the goal of this research lies in verifying the most popular visions on VAT’s influence on Russian macroindicators. The methodology of the research comes from the concepts recognizing taxes as an effective tool. The author applies general scientific and econometric methods (correlation, analysis of variance, and regression analysis) using MS Excel. The author formulates four hypotheses that have shown stable views about VAT’s influence on macroeconomy. They have been tested via six equations of linear regression; the significance of the equations has been estimated via the coefficient of determination, Fisher criterion, the average error of approximation; the significance of the coefficients d — via p-value and Student’s t-criterion. Each equation is statistically significant reliably reflecting the relationship between the resulting and factor. The obtained results have proven the 2nd and 4th hypotheses. Conclusion: VAT is directly related to consumer spending, gross profit and gross mixed income, intermediate consumption, and export. VAT refund stimulates export and investments to capital assets. The results of research could be considered as an arguments of proposals to changing the procedure for calculating and paying VAT in Russia.

Titanium and its alloys form a thin amorphous protective surface oxide when exposed to an oxygen environment. The properties of this oxide layer are thought to be responsible for titanium and its alloys biocompatibility, chemical inertness, and corrosion resistance. Surface oxide crystallinity and pore size are regarded to be two of the more important properties in establishing successful osseointegration. Anodization is an electrochemical method of surface modification used for colorization marking and improved bioactivity on orthopedic and dental titanium implants. Research on titanium anodization using sulphuric acid has been reported in the literature as being primarily conducted in molarity levels 3 M and less using either galvanostatic or potentiostatic methods. A wide range of pore diameters ranging from a few nanometers up to 10 μm have been shown to form in sulfuric acid electrolytes using the potentiostatic and galvanostatic methods. Nano sized pores have been shown to be beneficial for bone cell attachment and proliferation. The purpose of the present research was to investigate oxide crystallinity and pore formation during titanium anodization using a pulsed DC waveform in a series of sulfuric acid electrolytes ranging from 0.5 to 12 M. Anodizing titanium in increasing sulfuric acid molarities showed a trend of increasing transformations of the amorphous natural forming oxide to the crystalline phases of anatase and rutile. The pulsed DC waveform was shown to produce pores with a size range from ≤0.01 to 1 μm(2). The pore size distributions produced may be beneficial for bone cell attachment and proliferation.

Electrodeposition of diamondlike carbon films through oxidation of acetylides (prepared both in situ and ex situ) dissolved in dimethylsulfoxide (DMSO) was carried out at room temperature by potentiodynamic, potentiostatic, and galvanostatic methods onto gold substrates. Diamondlike carbon films (and nanoinclusions of diamond, graphite, and lonsdaleite phases) were prepared from acetylene-saturated liquid ammonia at a temperature of by potentiodynamic, potentiostatic, galvanostatic, and pulsed deposition methods. The films were characterized in situ by electrochemical methods and ex situ by Raman spectroscopy, optical microscopy, transmission electron microscopy, profilometry, and electron diffraction. Films were successfully deposited by both methods. The fastest growth rate was achieved with acetylides prepared ex situ and oxidized in the presence of in DMSO solution. Film thickness was found to increase either by processing at higher values of potential or for longer deposition times. Films of the highest quality and greatest uniformity were prepared by pulsed deposition from acetylene-saturated liquid ammonia. Nanodiamond and lonsdaleite inclusions were obtained by potentiostatic deposition from the same medium.

To avoid the numerous experiments for determining optimal conditions and electrolyte composition at co-deposition of two metals we have cleated the regression equation. Mathematical calculations have been carried out using the Optum ME package program with the study of some factors as current density, concentration of main components, temperature, etc. which effect on the co-deposition process. Three independent variables have been selected. The amount of molybdenum in the deposit has been chosen as the dependent variable. The developed regression equation quite adequately describes the co-deposition process of nickel with molybdenum and can be used at planning the works on obtaining alloys with the required composition by the electrochemical method

Heterogeneous catalysts play an important role in accelerating chemical reactions in order to save energy and cost during the reaction process. Platinum (Pt) has received a great deal of attention for its application in many catalytic processes, but very few studies have evaluated it in the hydrogenation process of acetone. In this study, Pt particles were successfully grown on an indium tin oxide (ITO) coated glass substrate by means of a facile, one-step, and template-free electrodeposition method using a solution containing 2.0 mM H2PtCl6 and 0.5 M H2SO4 at room temperature. Potentiostatic and galvanostatic methods were employed to conduct the electrodeposition process under different potentials, current densities, and deposition times to observe their influence on the morphology of the electrodeposited Pt particles. It was found that the morphology of the particles could be facilely manipulated by adjusting the deposition current and potential by using the galvanostatic and potentiostatic methods, respectively. The potentiostatic method produced a spherical or bayberry-like shape whereas the galvanostatic method produced a flower-like shape. The sharp tips on the surface of the bayberry-like shape are electron-rich sites that can break the C = O bond in acetone, thereby forming C-OH bonds that can generate isopropanol molecules.

The effect of electro-polymerization method on supercapacitive properties of poly (o-Anisidine)/CNT nanocomposites

Linear and geometric regression equations were used to estimate liveweight of two hundred and eighty six semi-intensively managed West African Dwarf (WAD) goats from Chest girth (CG) and Wither height (WH) measurements. CG accounted for 52 and 58% variation in the liveweight of goats using linear and geometric equations respectively, thus showing a curvilinear relationship. WH accounted for 31% variation in liveweight of goats using both equations. CG measurement was found to be more reliable for estimating liveweight of WAD goats than WH measurement. Using linear regression equation, CG and WH estimated the liveweight of females better than males with average increases of 57% and 25% R' values respectively. Using geometric regression equation, CG and WH also estimated the liveweight of females better than males with average increases of 55% and 22% R' values respectively. In essence, CG and WH measurements estimated the liveweighi of does better than bucks using both regression equations. Generally, CG and WH better estimated the liveweight of goats that are greater or equal to 3 years old than goats that are greater than / year but less than 3 years old and goats that are less or equal to 1 year old using both regression equations. Even though, each of the geometric or linear regression equations may be used to estimate liveweight of WAD goats with a high degree of reliability in a specific class of animals, it would be simpler and less cumbersome to use the regression equation obtained from pooled data to estimate liveweight in all animals

The purpose of the article is to determine the development trends and factors of influence of international tourism in the regions, on the basis of correlation and regression analysis, the relationship of dependent variables with other variables is determined, the return on investment in fixed assets is calculated and conclusions are drawn based on the results of correlation and regression analysis. The study analyzed data from UN Tourism, the world leader in the field of tourism, as well as research works by world scientists interested in the rapid development of the tourism industry. The identification of development trends and factors of influence of international tourism in the regions through the multiplicative and synergetic effect of tourism, the achievement of economic development of the country, as well as the effective use of internal resources reveal the relevance of the article. In analyzing the article, the following research methods were used to achieve the results of correlation and regression analysis, to build a dynamic model, a correlation matrix was applied for indicators for the Almaty and East Kazakhstan regions, using correlation and regression analysis, factors with a close statistically significant relationship with dependent variables were identified. Summing up, the authors came to the following conclusion: in the Almaty and East Kazakhstan regions, we achieved a statistically significant and reliable relationship between the performance characteristic and factor characteristics at the same time, the obtained regression equation as a whole and regression coefficients at the appropriate levels of significance. Based on the return on investment and analysis of the obtained parameters of the equation of multilinear regression, the authors believe that an increase in the number of rooms in tourist accommodation at the growth of GRP per capita by 1 thousand tenge and an increase in the number of rooms in accommodation facilities by 1 unit will lead to an increase in the number of services provided related to tourist accommodation facilities.

Introduction/objective. The significant part of young people in the structure of hepatitis C virus (HC/HCV infection) incidence, a lot of latent cases of this infection, and the lack of specific prevention may complicate the epidemic situation regarding this infection in Ukraine in the coming years. The authors developed a mathematical model of the HC epidemiological process to determine the most significant factors in this infection transmission in the country. Materials and methods. The study is based on correlation-regression analysis of the relationship between a dependent (or responding) and explanatory (factorial or predictors) variables. In total, the analysis involved 3 dependent variables y1, y2, y3, corresponding to the annual number of acute and chronic HC cases and the number of HC virus seropositive individuals, and 17 predictors x1 – x17, including patients who received etiotropic treatment; patients with mental and behavioral disorders due to narcotics use, including opioids; patients with sexually transmitted infections; the number of visits to dentists; the number of patients who had dentures placed; the number of surgical operations, blood transfusions, endoscopic examinations, laboratory blood tests, hemodialysis, etc. The number of observations (n) of dependent and explanatory variables was equal to 25, which corresponds to the number of administrative-territorial units in Ukraine (24 regions and Kyiv). The quality of regression models was evaluated using multiple correlation coefficients (R), determination coefficients (R2), and regression coefficients (b0, b1, b2). Statistical significance of R2 was determined by F-statistics, regression coefficients – by standard errors (m), t-test, p-value, and the range of 95% confidence intervals (CI). To compare the degree of influence of factor variables over dependent variables in the two-factor regression model, standardized regression coefficients were calculated. The reliability of regression models was evaluated by the statistics of Durbin–Watson (DW), Breusch–Godfrey (BG), and White (W) tests. The relative risk (RR) of HC infection was retrospectively determined in individuals from behavioral and medical risk groups. Results. In mathematical model of the epidemic process of acute HC, statistical significance was demonstrated for only one variable effect – annual number of dentist visits. The obtained regression equation was as follows: y1 = 0.000021 x5 – 11.353, where y1 = annual number of patients with acute HC; х5 = annual number of dentist visits. Statistical characteristics of the model: R = 0.892, R2 = 0.796; F-test: 89.9 for 1 and 23 degrees of freedom, statistical significance for F: 0.0000000021; regression coefficients: b1= 0.000021 (m = ±0.0000023; t = 9.48, tcrit = 1.71; p = 0.0000000021; 95% CІ [0.000017; 0.000026]), b0 = -11.353 (m = ±3.982; t = 2.85, tcrit = 1.71; p = 0.009; 95% CІ [-19.59; -3.116]). When developing a model of the epidemic process of acute HC taking into account the annual number of seropositive individuals, statistical significance was demonstrated only for two variables: annual number of the sexually transmitted infections and annual number of laboratory blood tests. The analytical relationship of variables in this model had the following mathematical expression: y3 = 4.563 x4 + 0.0058 x15 – 36552.721, where y3 = number of HCV-seropositive individuals; x4 = number of sexually transmitted diseases, x15 = number of laboratory blood tests. Statistical characteristics of the model: R = 0.92, R2 = 0.842; F-test: 58.62 for 2 and 22 degrees of freedom, statistical significance for F: 0.00000000153; regression coefficients: b0= -36552.721 (m = ±10649.1; t = 3.43, tcrit = 1.71; p = 0.0024; 95% CІ [-58637.63; -14467.81]), b1 = 0.0058; m = ±0.00082; t = 7.1, tcrit = 1.71; р = 0.0000004; 95% CІ [0.0041; 0.0075]; b2 = 4.563; m = ±1.526; t = 2.99, tcrit = 1.71; р = 0.0067; 95% CІ [1.4; 7.73]. The Durbin–Watson and Breusch–Godfrey tests did not reveal autocorrelation of residues for both regression models: DWU < DWр < 4 – DWU; BG < χ2. White's test shows no heteroscedasticity for both models: W < χ2. The test results indicate the reliability of both regression models. Conclusions. According to our data, at least 84% of HC virus infection cases in Ukraine occur through sexual contact and during laboratory blood sampling, and the role of the latter route of transmission in the HC virus spread was even more significant (standardized regression coefficients are 0.3 and 0.7, respectively). Almost 80% of acute HC cases are associated with dental interventions. Etiotropic treatment of patients with HC at the current level of treatment coverage can reduce the incidence of complications and the risk of death, but it is ineffective as a measure of influence on the first stage of the epidemiological process (source of infection). Drug users have little effect on the intensity of the HC epidemiological process in Ukraine as a whole, despite the fact that the relative risk of HC among this population is quite significant (RR = 6.5; 95% CI [6.39; 6.63]).

Corrosion rates from low polarization data calculated by a galvanostatic, non-linear curve fitting method

Purpose. Determination of the optimal unit operating parameters and molybdenum content in the coating. To achieve optimal performance and proper physico-mechanical properties, it was necessary to conduct a full factorial experiment. Methods. The chosen factors were: asymmetry coefficient, cathode current density within the range of 20–60 A/dm 2 , and Molybdenum disulfide concentration within the range of 0.2–3.4 kg/m 3 . The resulting function chosen was microhardness. Since preliminary research indicated that the response functions should be nonlinear, the factors had three variation levels. An orthogonal central composite second-order design was used to find the polynomial coefficients. The significance of the regression coefficients was checked using Student's t-test, and the adequacy of the obtained equations was verified using Fisher's F-test. Results. As a result of the conducted experiments and statistical data processing, a regression equation in coded form was obtained, linking the coating's microhardness with the studied parameters. Analysis of the coefficient significance showed that the MoS 2 concentration has the greatest influence on microhardness. The interaction effects of the factors were also statistically significant. The calculated value of Fisher's criterion was F = 3.87, which is lower than the tabulated value (Ftab = 19.4) at a 95 % significance level. Consequently, the obtained regression equation adequately describes the electrodeposition process within the studied region. Conclusion. The method of mathematical experiment planning was successfully applied to optimize the process of electrodeposition of coatings alloyed with Molybdenum disulfide. An adequate second-order regression equation was obtained, linking the coating's microhardness with the asymmetry coefficient, cathode current density, and MoS 2 concentration. The results of the work allow for recommending optimal coating application regimes for their use in conditions of increased wear and corrosion.

Purpose. Detection the relationship between the level of losses of a three-phase transformer and the power of distortion caused by current harmonics.. Methodology. During the research, the methods of determining power losses and additional losses in the elements of the electrical system from higher current and voltage harmonics, the visual programming method, the experiment planning method, and the orthogonal central composite plan method were used. Findings. An analysis of the indicators characterizing voltage and current distortions was carried out, and it was found that these distortions are most fully characterized by the current distortion power and voltage distortion power. These indicators are used to analyze the transmission of electric energy by a transformer of a traction substation. It is noted that the order of harmonics in the distortion power is not eliminated, and higher harmonics are taken into account by the corresponding effective current of higher harmonics. The specifics of the transformer secondary winding connections to the consumer, namely the grounding of one of the secondary winding phases, were taken into account. A number of combinations of current harmonics were used to simulate current distortions. The experiment was carried out using the planning method. The coefficients of the quadratic regression equation that relates power losses to the level of load current harmonics of the third, fifth, and seventh orders are obtaine To determine the significance of the obtained coefficients of the regression equation, the variances and the corresponding values of the Student's criterion were calculated, as a result, factors that do not affect the process and can be excluded from the regression equation were identified. The adequacy of the obtained regression equation was checked by Fisher's criterion. The analysis of the effects and their interaction showed that the standard error of the sample does not exceed 1.66%. As a result of analyzing the combinations of current harmonics that were set during the experiment, it was noted that some of them lead to the same effective phase current, while the power of current distortion is different. The greatest significance of the level of the third harmonic of the current is determined. The constant level of active power on the high voltage side of the transformer is noted, which is due to the absence of voltage distortions on it. Originality. Cases of combinations of current harmonic levels at which the current distortion power index remains unchanged, while the level of transformer power losses caused by current harmonics changes, have been identified. Practical value. This research can be used to assess and reduce the level of power losses in a transformer by filtering certain current harmonics.