bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of Process Rolling Plates from Alloy of Al-Mg System Economically Doped with Scandium
Authors: Sidelnikov Sergey , Dovzhenko Ivan , Belokonova Irina
Published: April 2021

The modes of hot and cold rolling of plates from an alloy of the Al-Mg system alloy, doped with scandium in the range of 0.10-0.12%, are modeled. At the first stage of work, using the DEFORM-3D software package, we simulated the process of hot sheet rolling at the Quarto 2800 mill, in order to obtain a billet for further cold rolling. Analysis of the simulation data showed that with the adopted compression mode, the metal forming and temperature conditions of rolling make it possible to obtain plates up to 45 mm thick, without defects, with rational power loading of the equipment. Further modeling of the regime of cold rolling of plates with a thickness of up to 31.5 mm showed that cold rolling can be carried out in 4 passes, provided that the stress and rolling force do not exceed the permissible values. At the second stage of work, we conducted an experimental verification of the obtained simulation results both in industrial and in laboratory conditions. It was found that the value of the total compression leading to the destruction of the samples, depending on the rolling conditions, should not exceed 21-30%. At this degree of deformation, the rolled metal from the alloy under study has high strength and plastic properties. Subsequent industrial verification of the research results confirmed that this alloy is quite advanced technologically, while it has high deformability, both during hot and cold rolling, which allows us to recommend it for sheet deformed semi-finished products in the manufacture of structural products for various purposes.
Specific Features of Statistical Analysis for Grain Nanostructures Formed by Solid-State Diffusion at Annealing
Authors: Stolbovsky Alexey V.
Published: April 2021

Analysis of structure of Nb3Sn layers, formed by solid-state diffusion in Nb/Cu-Sn composites, has been carried out, using statistical analysis methods. The three different statistical models of grain size distributions, which consist of both a single logarithmic standard distribution and a combination of a logarithmic and a standard distribution with scale factors were considered. It was shown that, during the formation and further evolution of the structure by solid-state diffusion processes, there is a strong correlation between the average crystallite sizes and their deviations from mean values. The dependence of the standard deviation on the average crystallite size, calculated from parameters of logarithmic distribution, falls on the straight line with small deviations. Taking into consideration the relationship between the parameters of grain size distribution, one can conclude that an approximation with the model which involves the dependence between standard deviation of the standard distribution and the logarithmic one provides better accuracy, despite a little bit worse fitting quality of the experimental distributions.
Synthesis and Catalytic Properties of CoFe2O4/Fe2O3 Nanosized Composite Material
Authors: Shabelskaya N.P. , Egorova M.A. , Vasilieva E.V.
Published: April 2021

The present research is devoted to the formation process of a nanoscale composite material with the composition of CoFe2O4/α-Fe2O3. The synthesized material has been studied by the following methods: x-ray phase analysis and scanning electron microscopy. The produced sample is analyzed to be a CoFe2O4 cabic spinel with a unit cell parameters of a = 0.8394 nm and α-Fe2O3. The average crystallite size of the resulting samples, determined by the Debye-Scherrer equation, is 4.8 nm for the cobalt (II) ferrite and 7.9 nm for α-Fe2O3. Reaction rate increase is determined by the incease in hydrogen peroxide amount in the solution. The synthesized composite material is found to exhibit increased catalytic activity in the oxidative degradation reaction of organic dye by hydrogen peroxide. The catalytic activity is established to be particularly high, when the process is occurring in acidic medium. The obtained samples have a highly developed surface and may be of interest as catalysts, adsorbents.
Development of Arc Welding Technology with Support of Stability of Electrode Melting Process
Authors: Sidoruk V.S. , Maksimov S.Yu. , Krazhanovskyi D.N.
Published: April 2021

Mechanized arc welding is divided into two main varieties: with self-regulation of the electrode melting process and with automatic process control. The common thing between self-regulating mechanized arc welding and manual arc welding is that in the welding equipment there are no means for automatic control with feedback from the arc. The difference between them is that stabilization of the electrode melting process in mechanized welding is carried out by the source itself, which has a particular volt-ampere characteristic (CVC), by a corresponding spontaneous reaction to a change in the situation in the arc. This method is significantly inferior to the method with automatic process control in precisely maintaining the specified parameters and has a limitation on the minimum current density on the electrode. The method of pulse self-regulation of the electrode melting process proposed in the E.O.Paton EWI removes this problem. However, it requires the use of power sources with a complicated, multi-link CVC curve. Further improvement is revealed through the use of digital controlled, programmable power supplies that have an automatically generated CVC. The combination of automatic source control and self-regulation by the spontaneous reaction to the situation in the arc creates a new hybrid way to stabilize the process of arc welding with a consumable electrode and other related arc processes (surfacing, soldering, re-melting).
Researching of the Efficiency on the Application for Complex Processing in Obtaining the Different Types of Surfaces
Authors: Inozemtcev Vitaliy E. , Kulikov Mikhail Yu. , Evseev Dmitry G.
Published: April 2021

The influence of the effect of combining different types of processing based on the physical force acting on the surface of conductive materials and the electrochemical active action of electrolytes acting as a cutting fluid is considered. The experiments carried out and show a significant effect of these types of processing on the surface quality and the provision of the initial various physical and mechanical properties of the processed materials. The article presents various dependencies of qualitative parameters for the implementation of shaping processes using such blade processing operations as turning, threading in holes of small diameter and expanding the holes. With combined processing methods, the process of forming the finish surface is due to the combined action of the cutting tool and the anodic dissolution of the metal under the influence of an electric current in the electrolyte solution. The application of this method allows obtain higher quality parameters when machining aluminum and copper alloys, the surface formed during processing, including the preservation of such special characteristics of certain materials, such as porosity.
Research of Mechanochemical Corrosion of Steels С1020 and А516-55
Authors: Tyusenkov A.S. , Nasibullina O.A.
Published: April 2021

During operation many metal structures are under conditions of combined impact of aggressive media (natural and/or technological) and mechanical loads. At the same time, the damage caused by the combined effect of corrosion and stress is often more significant than with simple "superimposing" of damage caused by mechanical load and influence of aggressive medium acting separately. When carrying out destructive tensile tests of equipment materials, there is a possibility of inaccuracy of results for determination of mechanical characteristics of this material due to actual operation of the material under conditions of aggressive environment. This, in turn, can lead to an erroneous calculation of the strength and life of the equipment. In this regard, it is particularly relevant to study the behavior of materials under the influence of various mechanical loads in aggressive media, as well as to determine the limit state of the metal based on the results of measurement of its electrode potential.
Electrochemical Processing of Metal Wastes of Rhenium-Containing Heat-Resistant Nickel Alloys
Authors: Agapova L.Ya. , Kilibayeva S.K. , Zagorodnyaya A.N.
Published: April 2021

The paper presents the results of studies of electrochemical processing of large pieces of metal wastes of rhenium-containing heat-resistant nickel alloys (HRNA) with subsequent processing of the products of electrolysis. It shows the possibility of electrochemical processing of large (up to 2 kg) scrap pieces, without preliminary grinding, in sulfuric acid solution with nitric acid addition, under the current density of 500-1000 A/m2, with a temperature of 30-40о С. Up to 80-90% of rhenium and over 90% of nickel, cobalt, chrome and aluminum can be converted into the solution. Tungsten, tantalum and hafnium remain in the anode slime almost completely. Rhenium, nickel and cobalt remaining in the anode slime can be transferred to the solution, when the slime is chemically processed in sulfuric acid solution with nitric acid addition. The cake remaining after chemical decomposition of anode slimes represents a concentrate of refractory rare metals, containing up to 42% W; 18% Ta; 4% Hf. Rhenium is extracted from the combined solutions from anodic decomposition of HRNA wastes, and chemical dissolution of anode slimes, by the known extraction method in the form of the crude ammonium perrhenate (68,9 mас. % Re). After rhenium extraction the raffinate contains considerable quantities of nickel and cobalt, which can be precipitated by the alkali solution in the form of hydroxides to the nickel-cobalt concentrate, containing 31.5% Ni and 4.8% Co.
Processing Technogenic Raw Materials-Phosphorus Slags with the Production of Precipitated Nanosilica and Simultaneous Recovery of Valuable Components
Authors: Bochevskaya Yelena G. , Karshigina Zaure B. , Sharipova Aynash S.
Published: April 2021

The paper provides a flow sheet of the phosphorus slag processing to produce precipitated silica (white soot). The process conditions for opening phosphorus slag at the I stage of leaching have been selected: the nitric acid concentration is 3.5 mol/dm3; the ratio S:L = 1:3.5; the temperature is 60 oС; and the process duration is 1 hour. The parameters of the white soot production II stage have been determined: the HNO3 concentration is 6.5 mol/dm3; the ratio S:L = 1:3.5; the temperature is 50 oС; and the process duration is 1 hour. The temperature effect on the white soot structure and the specific surface have been established. At optimal process parameters, the white soot batches have been obtained with the main SiO2 component content of 88.2 and 90.5 %, and a specific surface of 170 and 182 m2/g, respectively. The through recovery of silicon into a commercial product is 98.0 % of its initial content in slag.
Processing of Hydro-Mineral Lithium Raw Material of Kazakhstan Using Inorganic Sorbents
Authors: Karshigina Zaure B. , Abisheva Zinesh S. , Bochevskaya Yelena G.
Published: April 2021

The article presents the results of studies on recovery of lithium from reservoir brines using both commercial and synthesized aluminum hydroxide and hydrated manganese oxide as sorbents. The research results showed that, when using commercial aluminum hydroxide and synthesized hydrated manganese oxide as sorbents, lithium recovery from brine was 21.8 and 20.1%, respectively. Studies were conducted on lithium chemisorption on freshly precipitated aluminum hydroxide, which was obtained by adding aluminum chloride solution and tri-calcium hydro-aluminate to the brine. Chemisorption of lithium was carried out under the following conditions: T = 50 °C; AlCl3 solution concentration - 120 g/dm3; molar ratio Li/Al = 7; pH equal = 8.0-8.8; holding time with stirring 1 h. The degree of lithium extraction from brine was 71%; lithium capacity of freshly precipitated Al (OH)3 was 5.9 mg/g. During calcareous leaching of lithium-aluminum precipitate, lithium was extracted into a solution by 74.7%.
Thermodynamics of Copper Arsenious Raw Materials Dissolution in Nitric Acid
Authors: Dizer Oleg A. , Rogozhnikov Denis A. , Naboichenko Stanislav S.
Published: April 2021

This article describes thermodynamic study of hydrometallurgical method for processing of copper arsenious gold-containing raw material. Chemical and phase composition of the material were researched. Calculations of the Gibbs energy change were conducted for possible reactions of the main minerals, present in the raw material, with nitric acid. Eh-pH diagrams and solid/liquid equilibrium distribution diagrams, which were constructed in order to confirm the possibility of obtaining the required reaction products through nitric acid leaching of the studied raw material.
The Study of Destructible Annealed Anode Paste in the Current CO2
Authors: Belousova Olga V. , Kostina Ksenia V.
Published: April 2021

The article is devoted to the study of destructibility of the annealed anode paste of different composition in the CO2 current. It is shown that the destructibility of CO2 current of petroleum coke is much less than that of pitch coke. The comparison of the qualitative characteristics of the anode paste on the basis of pitch coke and petroleum coke revealed the advantage of petroleum coke, due to its low sodium content. The average destructibility of the anode paste on the basis of different grades of cokes in the CO2 current is determined. The conducted semi-industrial tests were in good agreement with the laboratory studies.
The Study of the Melting of Waelz Oxide with an Increase in the Temperature of the Calcination Process
Authors: Ryazanov A.G. , Senin A.V. , Nasonov V.D.
Published: April 2021

Waelz-oxide is a raw material for the production of metallic zinc. Waelz-oxide contains impurities of zinc and lead chlorides and fluorides. Halides have a negative effect on the process of zinc electrolysis. Halides have a relatively low boiling point; therefore, they are removed into the gas phase by calcining Waelz-oxide at 800–850 °С. To intensify the process, calcination is sometimes carried out at elevated temperatures of 1100–1250 °С. However, an increase in temperature leads to partial melting and granulation of the calcined product. In the present work, the chemical and phase composition of the initial and calcined Waelz-oxide was studied. Thermodynamic modeling of phase and chemical transformations of Waelz-oxide components during heating has been performed. Experiments on calcination of Waelz-oxide in laboratory conditions at temperatures of 600–1250 °C were carried out. It was found that partial melting and granulation of Waelz-oxide is the result of the formation of fusible eutectics containing lead oxide. Lead oxide is formed as a result of decomposition of lead sulfate when heated above 1100 °C. A similar effect is not observed at a standard calcination temperature of 850 °C.
Determination of Properties of Wear-Resistant Coatings of Metal Forms
Authors: Gavariev Renat V. , Savin Igor A. , Gavarieva Ksenia N.
Published: April 2021

Among the many different ways to improve the performance of molds for injection molding, there are those that are based on the application of thin multi-layer wear-resistant coatings by cathode-ion bombardment. However, due to the relatively small thickness of the applied coatings, measuring their parameters is a difficult task. Therefore, the article considers methods for determining the main parameters of thin multilayer coatings, such as: microhardness, separation and crack resistance coefficients, Young's modulus. The results of measurements of several coatings of different compositions are presented.
Influence of Contact Efforts on the Surface Quality of Difficult Profile under Finishing Hardening Machining
Authors: Sukhochev Gennady A. , Sokolnikov Vasiliy N. , Nekrylov Andrey M.
Published: April 2021

This work presents the research and development data in the field of finishing and hardening processes for parts with complicated shape surface. The comparable effectiveness of different surface finishing and hardening processes were studied, and intensification possibilities of processes of vibration finishing - hardening machining of narrow ducts by means of combined methods with metal anodic dissolution were shown. The results of experimental researches of influence of extrusion conditions of granular media on the surface layer quality are presented.
Alumo Matrix Composite Materials for Electro Spark Deposition on Carbon Steel
Authors: Nikolenko Sergey V. , Khimukhin Sergey N. , Gordienko P.S.
Published: April 2021

The article presents the research results on the problem of the influence of the electric spark discharge parameters and electrode alloys, based on metal matrix materials, used for electro spark deposition (ESD) on the physicochemical and operational characteristics of the coating layer. Experimental dependences of the cathode weight gain, erosion resistance of the anode materials, mass transfer coefficient, wear resistance of the coating, and their mathematical expressions with a reliability criterion of at least R2> 0.9044, are obtained. It is established that, after steel 45 sample has been treated by ESD with metal-matrix materials, the hardness of its surface increases 6 times on the average and the wear resistance – 2 times. The best values of wear resistance at all the modes under investigation have been obtained for the anode material NiO-Zr-TiO2-Al. Data series of cathode weight gain (ƩΔc), erosion resistance of anode materials (ƩΔа), mass transfer coefficient Кmt, coating wear resistance after ESD (Ʃcwr), coating formation efficiency (γcfe), ESD energy efficiency (γeef), are also obtained. These data can be recommended for achieving the required parameters of the ESD on steels using metal-matrix materials.
A Study of Reactivity of Model Compounds of Lignin Biopolymer
Authors: Karimov Oleg Kh. , Kolchina Galina Yu. , Movsumzade Eldar M.
Published: April 2021

In the framework of method of the B3LYP hybrid density functional and the restricted Hartree-Fock method, quantum-chemical calculations of model compounds of lignin, i.e. derivatives of p-hydroxycinnamic alcohol were carried out. The structures and reactivity of coumaric, coniferyl and synapol alcohols were studied. Quantitative characteristics of the reactivity of these acids are given. It is found that the electronic structure of lignin is determined primarily by the charge distribution in its structural phenylpropane unit. In the molecules of all model compounds of lignin, the center for nucleophilic attack is the carbon of aromatic ring (E-ring) with a hydroxyl group, and in the molecule of synapol alcohol, this center is also the carbon of the aromatic ring (E-ring) with a methoxy group. In all three compounds, a center with an increased electron density appears on the Сβ carbon atom.
Coatings and Lubricant to Forming Surfaces of Molds for Casting under Pressure
Authors: Gavariev Renat V. , Soldatkina Elena N. , Gavarieva Ksenia N.
Published: April 2021

The article considers the main points for choosing lubricants, taking into account the specifics of the injection molding process. The main drawbacks of modern lubricant compositions are identified, and based on them, the main requirements for lubricants for injection molding are determined. The most critical parameters of lubricants are specified, depending on the melt to be filled. The methods of applying lubricants are considered, and the most optimal ones are selected.
Development and Research of Copper Covering for Intensification of Cold Stamping of Products from Stainless Steels
Authors: Karzhavin Vladimir V. , Maltsev Lev V. , Bakina Viktoriya V.
Published: April 2021

The copper covering put in fused salts of chlorides at temperature of 450-500cC and preventing scuffs on the surface of steel of type 12X18H10T at cold stamping of case products and fixture was investigated. Metallurgical surveys have shown: 1) except cover zone and zone of base metal there is also transition zone, representing substitution type of solution; 2) in the course of application there is superficial alloying, due to penetration of atoms of copper deep into metal and diffusions of doping steel elements in coating material under the influence of melts's high temperature. The schedule of change of concentration of copper in diffusion zone allows to conclude that the copper covering consists not of pure copper, and that the alloy contains only 94% of copper; other 6% represent the chrome and the titanium diffusing in copper covering. It is established also that, despite strong cohesion with basis, the covering is completely removed from surface of the stamping details being dissolved in standard sulphuric acid solution.
Experimental and Numerical Study of the Hybridisation Effect on the High-Velocity Impact Resistance of Thermoplastic Composites Based on Aramid Fabrics
Authors: Zhikharev Mikhail V. , Kudryavtsev Oleg A. , Ignatova Anastasia V.
Published: April 2021

One of the urgent tasks of the development of new protective structures is to improve the ballistic performance of thermoplastic composites reinforced with synthetic high-strength fibres. Hybrid composites based on various types of fibres or fabrics with different weaving could be a possible solution to this problem. This paper presents the results of computational and experimental studies of hybrid composites based on aramid fabrics with satin and plain weave structures. Numerical modelling based on the reduced ply-level approach was used for the design of hybrid composites. The results obtained during calculations were in good agreement with validation experiments.
Transformation of Chemical and Phase Composition in Al/FeAl3(Cr,Ni)/Fe2Al5(Cr,Ni) Laminated Coating at High Temperature Heating
Authors: Shmorgun Victor Georgievich , Kulevich Vitaliy P. , Kharlamov Valentin O.
Published: April 2021

The effect of thermal action at 1100 °C on the kinetics of phase transformations in the coating, obtained by hot-dip aluminizing of 12Cr18Ni10Ti steel, is studied. It was shown that, after 500 h of exposure, the chemical composition is leveled over the entire volume of the sample. Moreover, the predicted retention time of the heat-resistant properties of the coating at 1100 °C is about 2000 h.
About Using Composite Materials when Restoring High-Resource Details with Application of Additive Technologies are Given
Authors: Yatsenko Svetlana N. , Penkov Nikita A. , Krasnov Andrey A.
Published: April 2021

The process of restoration of high-resource parts of equipment for various purposes using AM technologies is considered. This method can save significantly the material of the formed coating, while providing the necessary efficiency in increasing the wear resistance of the restored parts. The causes of the leakage from the resulting coatings are residual stresses. Using a regression analysis apparatus, recommendations for the selection of technological modes from coatings are determined. The kinematic features of the recovery process are taken into account, dynamic relationships for determining stresses in the formed coating are determined. To find the volume of work, a worn surface is scanned. Further creation of the composite coating is carried out, taking into account the degree of wear from each section, separately. The influence of technological parameters on the micro-hardness and thickness of the applied composite coatings is investigated. Recommendations are given on the development of production technology, using 3-D printing of composite metal coatings, that can increase the wear resistance of high-resource parts.
System of Chemical Bonds and Compounds as a Modern Scientific Foundation for Unification of Methods for Controlling the Structure and Properties of Various Substances and Materials
Authors: Sirotkin R.O. , Sirotkin O.S.
Published: April 2021

Modern scientific foundation for the unification of methods of control and analysis of structural features and practically important properties of various metallic and non-metallic polymeric, ceramic materials are considered. Within the framework of improving materials' control and analysis methods through taking into account the effects of chemical elemental composition on their structure and properties, a new fundamental approach was developed. This method, unlike others, is applicable to both metals and non-metals, and implies considering the impact of both the composition and the type of chemical bonding on structure and properties of materials. This was done on the basis of a unified multilevel classification of structure of metallic and non-metallic materials, the use of a unified model and system of chemical bonds and compounds, which allowed evaluating the effect of mixed types of chemical bonds on characteristics of their multilevel structure and properties.
Analysis of Wear-Resistant Materials of Mixer - Pneumosuperchargers Blades Operating under Conditions of Abrasive Wear
Authors: Gabelchenko Natalya , Belov Artem , Kravchenko Artem , Kryuchkov Oleg
Published: April 2021

We conducted comparative tests of the wear resistance of metals operating under abrasive conditions. Samples were cut from the working parts of mixer-pneumosuperchargers. The chemical composition and mechanical properties were determined. To compare samples under abrasive wear conditions, we designed and assembled a carousel installation. The principle of its operation is based on mixing the abrasive medium by the samples being studied with a given speed. Wear resistance was evaluated by weight loss by samples after several test cycles. To determine changes in the structure of the metal during abrasive wear, metallographic studies of the samples were carried out before and after the tests. It is shown that the best complex of service and mechanical properties is possessed by 110G13L steel.
Method for the Determining Metal Mechanical Characteristics Using FEM
Authors: Volokitina Irina , Panin Evgeniy , Tolubaev Kanat
Published: April 2021

In this paper the methods of mechanical testing of metal and the possibility of their implementation, using mathematical modeling by the finite element method in Deform software package, are considered. As the studied parameters, both the strength indicators (yield strength, tensile strength, Brinel micro-hardness), and the plasticity indicator (the number of kinks before the crack is formed), were studied. The values obtained in the simulation have a very high convergence with the real data.
The Use of Fractal Formalism for the Description of Microstructures Engineering Materials
Authors: Bakhracheva Yulia
Published: April 2021

In this paper, the structures of spatial self-organization of steels after thermos-cyclic exposure were studied, using the fractal formalism method. It is shown that the structures, observed after cyclic heat exposure, can be characterized by the presence of the invariance property of their structure at different scale levels.
Determination Coefficient of Stress Concentration Using a Conformed Display on a Circle of a Single Radius
Authors: Shapoval Oleksandr , Savchenko Iurii , Markov Oleg
Published: April 2021

Developed a mathematical model, which makes it possible to optimize, from the point of view of defect formation, the parameters of stress concentration in a deformable elastic body of the materials being processed, destruction is considered as a method for creating defects at a submicroscopic level in various media. Getting expressions of conformal reflection of single circle on an arbitrary area, using a conformal reflection and transformation of Laplace, it is possible to design behavior of a tensely deformed state of solid at the arbitrary loading.
Modeling the Stress-Strain Curve of Elastic-Plastic Materials
Authors: Golovina Natalya Ya.
Published: April 2021

The work is devoted to the formulation of mathematical models of plastic materials without hardening. A functional is proposed, the requirement of stationarity of which made it possible to formulate the differential equation of stress as a function of deformation. On the linear deformation section, a second-order functional is proposed; on the non-linear deformation section, a fourth-order functional is proposed. A range of boundary value problems is formulated, that ensure the continuity of the function at the boundary of the linear and non-linear sections of the deformation curve. The theoretical strain curve was compared with the samples of experimental points for materials: St3sp steel, steel 35, steel 20HGR, steel 08Kh18N10, titanium alloy VT6, aluminum alloy D16, steel 30KhGSN2A, steel 40Kh2N2MA, and showed a good agreement with the experiment. Thus, a variational model is constructed, that allows one to construct curve deformations of various physically non-linear materials, which will allow one to construct further mathematical models of the resource of such materials.
A Study on Chemical Durability of Fiberglass-Reinforced Plastic in NaOH Environment
Authors: Blaznov Aleksey N. , Firsov Vyacheslav V. , Zhurkovsky Maxim E.
Published: April 2021

Here we investigate the durability of glass fiber-reinforced polymer bars that were held for a long time (up to 360 days) at temperatures of 20 ºС, 60 ºС and 80 ºС in a NaOH solution (pH=13). A total of 22 specimen groups, including a control group of initial specimens, were tested. The fracture strength tests were performed by the longitudinal bend technique. The durability of the bars when held in alkali at 60 ºС and 80 ºС for up to 55 days was found to decline gradually and constituted 0.86 and 0.84 of the initial strength (86% and 84 %). After 55 days, the point of inflection occurred, and the durability began to decrease sharply, reaching the values of 0.49 (at 60 ºС) and 0.24 (at 80 ºС) at a residence time of 360 days. The durability diminished gradually at a room temperature of 20−23 ºС to attain the value of 0.91 at a holding time of 360 days. A mathematical model is suggested that approximates test results with reasonable accuracy, R2=0.9967, and the time when the conditions change (inflection of strength-to-time curve) was experimentally found to be 60 days.
Composite Materials with the Coating to Detect Barely Visible Impact Based on the Retroreflective Film
Authors: Buslaeva Olga , Sapozhnikov Sergey B.
Published: April 2021

A new method of indicating contact damage of composite materials, using a polymer retroreflective film (PRF) with micro-prisms, is proposed. Impact contact action leads to deformation of microprisms and with directed lighting allows seeing the place of impact in the form of a dark spot. In experimental studies, using STEF fibreglass as an example, the dependences of the spot diameter on the contact pressure up to 530 MPa were studied. An assessment of the residual strength and stiffness of a composite specimen-beam with a contact defect was obtained with three-point bending. It is shown that, during bending, the strength of STEF with contact defects decreases from 615 to 386 MPa. The data obtained allow to assess the danger of contact pressure by the known diameter of the dark spot on the PRF.
Change of the Elastic Characteristics of a Fiber-Reinforced Laminate as a Result of Progressive Fatigue Damage
Authors: Nikhamkin M.Sh. , Solomonov D.G.
Published: April 2021

It is a widely known fact that the stiffness of polymer composite materials decreases with the accumulation of fatigue damage under cyclic loading. The purpose of this article is to develop a method and obtain experimental data on decrease of the elastic characteristics of a fiber-reinforced laminate, as a result of progressive fatigue damage. The developed technique consists of two stages. At the first one, the natural frequencies and eigenmodes of the samples during their fatigue testing are experimentally obtained. The dependences of the natural frequencies of the samples on the number of loading cycles are found. At the second stage, the four elasticity parameters of the laminate monolayer (two Young modules, the shear module and Poisson's ratio) are identified via the natural frequencies. The inverse numerical/experimental technique for material properties identification is applied. The dependences of the natural frequencies and mentioned elastic characteristics on the relative fatigue life are obtained as experimental results of both modal and fatigue tests. The results can be useful to study the fatigue behavior of the investigated materials and to create methods for calculating fatigue life.
Estimating the Stress-Strain State of Roll by Temperature Gradient in the Course of its Heat Treatment
Authors: Savinov Alexander S. , Andreev Sergey M. , Feoktistov Nikolay A.
Published: April 2021

The paper considers the issue of mathematical simulating the stress-strain state of a roll in the course of its heat treatment. It is shown that a sound heat treatment schedule affects significantly the economic efficiency of a metallurgical enterprise. The mathematical apparatus is provided to estimate the thermal interaction in the casting-furnace system, based on which a program for calculating the thermal state of a roll during heat treatment has been developed. Using this program allows evaluating the thermal stresses occurring in a roll during the heat treatment cycle and reducing the risk of discontinuity in the roll cast billet. Also, using the program developed, allows significant reducing the engineer-technologist man-hours for the design of the process cycle of the casting heat treatment. An example of calculating the thermal state of a roll with a diameter of 930 mm in casting is given. The change in the dynamics of the maximum temperature gradient along the product radius is shown, while correlating it with the furnace setting.
Do sexual gonadic maturity and age determine habitat occupancy ofCanthon cyanellusLeConte, 1859 (Coleoptera: Scarabaeidae)?
Authors: Salomão Renato Portela , Arellano Lucrecia , Huerta Carmen , León-Cortés Jorge Leonel
Published: April 2021

High-quality habitats presumably have the resources required to sustain relatively high rates of survival and reproduction. We assessed how habitat type and local environmental conditions determine the distribution of individuals ofCanthon cyanellus(Coleoptera: Scarabaeidae), an eurytopic dung beetle, according to age category and sexual gonadic maturity. Beetles were surveyed in forest fragments, live fences, and pastures in Mexico. Individuals were categorised into six age categories according to the glandular volumes in males and oocyte number and length in females. Mature females in forest fragments were the most abundant females found among the habitats. Air humidity and soil hardness were positively and negatively related to mature female abundance, respectively. Mature beetles were the most abundant among males, and higher abundance of males occurred in forest fragments than in live fences and pastures. Light quantity was negatively related to the abundance of young males. Compared to forest fragments, females in pastures had larger oocytes. However, sites with higher soil hardness and air humidity had females with lower numbers of oocytes. Our results demonstrate that, althoughC. cyanellusoccurs across a wide range of habitats, forest habitats might host sexually mature individuals, which translates into more effective individual dispersion and potential reproduction.
Immunoreactivities of AR, ERα, ERβ and aromatase in the nuptial pad of Chinese brown frog (Rana dybowskii) during pre-hibernation and the breeding period
Authors: Tang Zeqi , Chen Yuan , Ren Baolong , Wang Xi , Zhang Haolin , Han Yingying , Yuan Zhengrong , Weng Qiang
Published: April 2021

There is a prominent local raised pad called nuptial pad on the forelimb of Chinese brown frog (Rana dybowskii), which is hypothetically concluded as an enhancement of the grip and a spreader of pheromone during the amplexus. In this study, we investigated the immunolocalization and protein expression levels of AR, ERα, ERβ and aromatase in the nuptial pad of R. dybowskii during pre-hibernation and the breeding period. Histologically, the annual development of the nuptial pad in R. dybowskii is manifested as the larger area of specialized mucous gland and the longer length of papillary epidermal projection during the breeding period. AR, ERα, ERβ and aromatase are present in the stratum granulosum, stratum spinosum, stratum basale and the secretory portion of specialized mucous glands during both periods. Western blotting results confirmed that AR, ERα and ERβ protein levels are higher during pre-hibernation than those during the breeding season. These results suggest that nuptial pad is the direct target organ of androgen and estrogen. Androgen may participate in the regulation of annual development and glandular function of nuptial pad, and estrogen may play an endocrine, autocrine or paracrine role during pre-hibernation and the breeding period.
Ischemic stroke in a patient with interatrial block: Is it only a coincidence or a clear relationship?
Authors: Antonopoulos Athanassios , Fiorani Laila
Published: April 2021

Atrial fibrillation (AF) can be detected in nearly 25% of all patients with stroke by sequentially combining different electrocardiographic methods. Prediction of early cardio-embolic stroke remain a permanent challenge in everyday practice. The early identification of an increased risk for atrial fibrillation episodes (which are frequently asymptomatic) is essential for the prevention of cardioembolic events. One of the noninvasive modalities of atrial fibrillation prediction is represented by the electrocardiographic P-wave analysis. This includes study and diagnosis of interatrial conduction block. Our short case report presents a case with ischemic cortico-sottocortical stroke involving capsulo and caudo regions in a woman patient with interatrial block as realized by electrocardiographic P analysis.
Portuguese validation of the credibility/expectancy questionnaire in routine practice
Authors: Silva Sara , Barbosa Eunice , Salgado João , Cunha Carla
Published: April 2021

This study aimed to validate and explore the psychometric properties of the credibility/expectancy questionnaire (CEQ) for the Portuguese population in the context of routine practice. The sample includes 87 clients from a university psychotherapy clinic. All clients completed self-report measures to assess credibility and expectation (CEQ), as well as measures of general mental health, depressive symptoms and therapeutic alliance in session 1 and session 2. The exploratory analysis revealed the existence of two factors in CEQ for the Portuguese population, factor 1 credibility and factor 2 expectation. The measure demonstrated good internal consistency, test-retest reliability and good adjustment in the confirmatory analysis. In terms of convergent validity, no significant correlation was found between credibility and expectation and the therapeutic alliance. The results corroborate the CEQ psychometric qualities for the Portuguese population, also showing its applicability in a context of routine practice.
Management of plantar fasciitis with Raktamokshana and Shamana Chikitsa in Ayurveda
Authors: Solanki Bhawna , Meher Ajaya , Bhatted Santosh Kumar , Dharmarajan Prasanth
Published: April 2021

Observation and Results:

The therapy provided marked improvement in the pain and tenderness. Pain from visual analog scale (VAS) of 8 came to 2, tenderness grading soft tissue scale from 5 came to 2.5, and PF pain/disability scale from 77 came to 2. It is the need of the hour to focus on such therapies which are result-oriented and less expensive. From this study, it can be inferred that this treatment can be effectively adopted in patients of PF.
Ayurveda Perspectives and Research Updates on Factors Influencing the Immunity
Authors: Thakur Rinky , Naik Raghavendra , Mythrey R. C. , Bhat Sulochana
Published: April 2021

The basic concept of immunity is well explained under the heading Vyadhi-kshamatva in classical texts of Ayurveda. A clear and comprehensive understanding of the relationship between immunity and lifestyle such as daily activities, seasonal regimens, diet, emotional factors, and psychological factors is documented in ancient literature. According to Ayurveda, the most important contributing factors for the normal immune functioning of the body include Agni (digestive factors), Ahara (food), Nidra (sleep), Vyayama (physical activity/exercise), Satva (mental stability), and Rasayana (rejuvenators). In the present work, these factors influencing immunity were compiled from classical texts of Ayurveda and presented systematically with the help of published scientific literature. It is observed that good immunity in an individual will be due to effect of active and healthy functioning of the digestive system. It depends mainly on the type of food consumed. Higher diet quality is associated with the positive health of the body. Quality diet, required quantity and balanced food, is the base for the proper digestion and in turn for the development of a strong immune system. Exercises improve metabolic health which in turn provides a good immune system. Even sleep affects the immune system. Good sleep provides strong immune responses; it results in the formation of antibodies which along with white blood cells cellular immune system of body and fight against the disease. A significant relationship is also reported between mental resilience and perceived immune functioning and health. Psychological well-being also can increase living comfort. Rasayana provides a defense mechanism against diseases (Vyadhi) in the body. Proper understanding and application of these concepts in clinical practice can be a preventive strategy for a number of diseases.
Management of lumbar degenerative spondylolisthesis by integrated naturopathy and Yoga therapy
Authors: Thanudhas Sujithra Sreekumari , Narayanasamy Mangairkarasi , Poornachandran Prabu
Published: April 2021

Spondylolisthesis is the forward displacement of a vertebra relative to the vertebra below, and it arises as a result of a pars defect. Lumbar degenerative spondylolisthesis is an established condition, and it classically involves the L4/L5 level with mild degenerative changes; the symptoms vary from lower back pain to lower limb radiculopathy depending on the severity. The present case reported was of a 57-year-old married woman diagnosed with lumbar degenerative spondylolisthesis after an accidental fall; her symptoms began with severe pain and numbness in both legs radiating from her buttock region. This case study was done to investigate the effectiveness of combined Yoga and naturopathy therapy in relieving degenerative pain. The subject received a specific yoga protocol, which includes Yogasanas, Pranayama, and relaxation techniques along with naturopathy treatments, including hydrotherapy, acupuncture, and natural diet therapy for 30 days. According to the findings of the visual analogue scale (VAS) and SF-MPQ-2 scale, the pain symptoms score changed from 9.2 to 1.3 and from 79 to 20, respectively. This result shows that the combined effect of Yoga and naturopathy treatment helps in relieving pain and improves the quality of life in patients with degenerative spondylolisthesis.
A Comparative Study of Coronavirus Cases in Gulf Cooperation Council Countries
Authors: Mohammed Rafiuddin
Published: April 2021

Objectives:

The first outbreak of COVID-19 was recognized in early March in Gulf Cooperation Council (GCC) countries and then accelerated at an exponential rate within a short period. The present study objective is to evaluate the prevalence of COVID-19 in GCC countries.

Methods:

Six countries are Saudi Arabia, Qatar, Kuwait, Bahrain, the United Arab Emirates (UAE), and Oman included in the study. Six parameters of COVID-19 data were collected from various dashboards. Data analyses of all parameters were expressed in frequencies and percentages.

Results:

The highest number of cases was reported in Saudi Arabia (347,282) and least in Bahrain (81,466). The cases in Saudi Arabia, Qatar, and Bahrain have been reported a decrease, while the UAE and Oman reported an increase in the month of October. The recovery rates in Qatar (97.76%) and the UAE (97.19%) showed highest. Saudi Arabia and Oman showed the highest death rate (1.56% and 1.06%), while Qatar lowest death rate (0.18%). Critical cases are more in Saudi Arabia (0.22%). Oman showed the highest number of active cases (8.88%). The highest percentage of COVID-19 infection rates are in Bahrain (4.75%) and Qatar (4.72%). The UAE (132.77%) and Bahrain (101.24%) reported the highest COVID-19-tested percentage, while Oman (7.32%) had the least in their given population.

Conclusions:

The status of COVID-19 in the UAE and Oman showed a slight increase in the cases. The overall outcomes represent the status of COVID-19 in GCC countries reliably under control. The strategies used by these countries played an extremely important role in preventing higher death rate and spread of the virus.
Assessing the Outcome of Implementation of Jigsaw Technique as a Learning Tool and its Effect on Performance of 1st Year Medical Students in Anatomy
Authors: Lalit Monika , Piplani Sanjay
Published: April 2021

Introduction:

Multiple factors in the contemporaneous trends in curriculum and medical education demand changes in teaching–learning methods with a dramatic change in the paradigm of teacher-centered teaching methods to student-centered learning methods. The jigsaw technique is an active learning methodology that involves active participation by the students in the learning process where they learn by teaching one another. It is an excellent potential tool to grasp an outsized load of information in a brief period or shorter time frame. The objective of the present study was to assess the effectiveness of the implementation of the jigsaw method as a learning tool during a graduate medical education setting.

Methodology:

The study was conducted among 150 phase I MBBS students during dissection in the department of anatomy. Two topics were decided and taught by didactic lecture. After taking the pretest, the topics were again taught by the jigsaw technique. After completion of the topic with this technique, students' knowledge regarding the topics was judged by taking a posttest. Pre- and postjigsaw technique assessment scores were calculated. The difference in the mean of pre- and posttests was estimated and compared by applying a paired-t-test to know the effectiveness of teaching methods.

Results:

The difference in the performance of the students in pre- and postjigsaw technique assessment scores test was calculated by applying paired-t-test which was found to be statistically significant (P < 0.001). About 100% of faculty members readily accepted the suggestion of implementing the jigsaw method. About 88% (132) of students showed enthusiasm and interest to take up the activity.

Conclusion:

There was an eloquent difference in the performance of the students in pretest and posttest knowledge scores. The results indicate a better performance by the students when they are involved actively in learning and found this method very helpful, interesting, and motivating.