bluuebunny/crossref_metadata_2025 huggingface dataset:
Ab initio study of electron and phonon coupling in silicon
Authors: Mliles Mustapha El , Kouari Youssef El , Hajjaji Abdelowahed
Published: November 2020

We have studied electron-phonon coupling in silicon and its relation to hot carriers thermalization. The calculation of electron-phonon and phonon-electron interactions in silicon was obtained from first-principles density functional theory and many-body perturbation theory. Electron and phonon relaxation times were calculated subsequently. Moreover, the results showed that silicon exhibits a relatively wide phononic band gap along the symmetry line X-W, which prevents the Klemens mechanism leading to a phonon bottleneck effect. As demonstrated, phonon-electron interactions can play an important role in mitigating the electron thermalization along this symmetry line. This work shade light on the importance of including the phonon- electron interactions in the ab initio approach for future semiconductor materials engineering.
Design and performance analysis of Rectenna Circuit
Authors: El Batal K. , Chakhchaoui N. , Eddiai A. , Meddad M. , Rguiti M. , Mazroui M. , Cherkaoui O.
Published: November 2020

Radio Frequency Energy harvesting is an extremely important research subject, linked to sustainability, and could be a potential solution to conventional energy supplies. The main idea is to develop battery-free wireless sensors able to capture the available energy into the mentioned bandwidth. In this paper, a 1.8–2.4 GHz wideband rectenna is designed for radio frequency (RF) energy harvesting in the context of wireless sensor nodes (WSN). For this purpose, the agilent Advanced Design System (ADS) was used. This article presents the design and simulation of a high output voltage rectifier. First, we designed a rectifier based on Metelics MSS20-141 Schottky diode using a series topology to convert electromagnetic energy into DC. Then, a low-pass filter was implemented to filter out undesirable harmonics generated by the non-linear Schottky diode. Simulation results show that load resistance, input frequency and input power are important parameters to evaluate the performances of RF energy harvester. Also, the three RF bands, GSM1800, UMTS and Wi-Fi, are considered. Therefore, the designed system has an average RF-to-DC conversion of 18 % for an incident power of -10 dBm for a variation of 20 to 1200 Ω.
PSPICE compact model for power MOSFET based on manufacturer datasheet
Authors: Galadi Abdelghafour
Published: November 2020

In this paper, large signal model for power MOSFET devices is presented. The proposed model includes quasi-saturation effect and describes accurately the electrical behavior of the power MOSFET devices. The large signal model elements will be provided based on the device structure. Furthermore, the model parameters are extracted from measurements considering the voltages depending effect of the nonlinear gate-source, gate-drain and drain-source interelectrode capacitances. Excellent agreements will be shown between the simulated and the datasheet data. Finally, a description of the model will be provided along with the parameter extraction procedure.
Global MPP Tracking for Photovoltaic Panel under Shading Conditions using Robust Numerical Algorithm
Authors: Mesbahi Oumaima , Kandoussi Khalid , otmani Rabie El , Hajjaji Abdeloawahed , Janeiro Fernando M. , Tlemçani Mouhaydine
Published: November 2020

This paper presents a new numerical approach for the modelling of the PV panels under partial shading conditions. It also solves the major drawback of the PV systems, which is the tracking of maximum power point under partial shading conditions where the P-V characteristic has a more complex structure with many local maximums on the graph. This paper aims to resolve this phenomenon using Newton method in order to find the global maximum power point.
Thermal performance of building materials based on feather and polystyrene wastes
Authors: Mrajji Ouahiba , El Wazna Mohamed , Ouhaibi Salma , Sair Said , El Bouari Abdeslam , Cherkaoui Omar , Belouaggadia Naoual
Published: November 2020

The development of composites using renewable resources has received attention of scientists over the last decade, with the aim of manufacturing environmentally friendly composites, reducing cost and the dependence on petroleum resources. This experimental study emphasizes the development of new cost-efficient composite based on feather/cotton nonwoven and polystyrene waste. The microstructure and thermal properties have been determined in each FPS material. Vacuum molding method was adopted for fabricating of the biocomposites with two contents of polystyrene matrix (30% and 50%). As a result, the morphological analysis revealed better compatibility and adhesion between the nonwoven and the polystyrene matrix. The manufactured composites showed an insulating character with thermal conductivity coefficient value of 35.95 and 33.85 mW / (m.K) respectively for the composite reinforced with 30 and 50% polystyrene. The origin of the variation of this property is due to densities and the percentage of the polystyrene matrix. The composites developed with polystyrene showed very high performance, combined with sufficient durability to be potential candidates for the development of new sustainable materials for the building sector.
Techno-economic investigation of electricity and hydrogen production from wind energy in Casablanca, Morocco
Authors: Touili Samir , Merrouni Ahmed Alami , Hassouani Youssef El , Amrani Abdel-illah , Azouzoute Alae
Published: November 2020

The aim of this study is to investigate the technical and economic potential of electricity and hydrogen production in Casablanca, Morocco. For this reason, we simulated the performance of a 4.2 MWp wind turbine if installed in Casablanca. The results show that the electricity and hydrogen production varies greatly through the year due to the high fluctuation in wind speed. The annual electricity and hydrogen production is 29.16 GWh and 555 Tons respectively. As for the levelized cost of production, the LCOE was found to be 0.24 $/kWh and the LCOH2

were equal to 13.52 $/Kg.
Theoretical study and Simulation method for optimizing the performance of advanced Energy Harvesting techniques
Authors: Elhmamsy Y. , Ennawaoui C. , Hajjaji A. , Boughaleb Y.
Published: November 2020

This paper investigates and compares the efficiencies of four different interfaces for vibration based energy harvesting systems. In some cases, the increase in power was found to be in the order of ten times the output power compared to the standard approach to energy harvested by piezoelectric materials. The authors updated the review of synchronous switching techniques used in the conversion of ambient mechanical energy to useful electrical energy using piezoelectric materials is given. The basic concepts involved in the standard energy harvesting approach and synchronous switch harvesting techniques are presented. A comparative analysis of these techniques, highlighting the strengths and limitations of each approach in terms of power conversion efficiency, load independence, implementation complexity and adaptability for system applications are discussed.
Permeate flux in air gap membrane distillation for seawater desalination
Authors: Rochd S. , Salama L. , Ghazaouy K. El , Mizani S. , Zerradi H. , El Marsi M. , Moultif R. , Dezairi A.
Published: November 2020

Membrane distillation (MD) is a thermally driven process since only vapor molecules are transported through porous hydrophobic membranes. This process leads to the separation into different desired phases. Air gap membrane distillation (AGMD) is considered one of the most used configurations of the membrane distillation. In this work, the impacts of NaCl concentration, porosity, and membrane pore size on the production of the flux have been investigated. The results have been carried using polynomial approximations through MATLAB. These latter are in agreement with the experiments.
Structural properties and spontaneous polarization behaviour in Cu-doped LiTaO3
Authors: Tahiri M. , Jennane A. , Masaif N. , Lotfi E.M.
Published: November 2020

In this work, we have study theoretically the effect of cooling modes on the changes of spontaneous polarisation (Ps) of non-stoichiometric solid solutions of Cu-doped LiTaO3 in correlation with the defects structure. The changes of spontaneous polarization in rapid and slow cooling modes with the rate of % Cu2+ and with the Curie temperature, allows us to analyse the defect structure of solid solutions synthesized in ternary system Li2O-Ta2O5-(CuO)2 in vicinity of LiTaO3. The theoretical results obtained by application of our approach combined with the proposed vacancy models; show that the cooling modes have an effect on the spontaneous polarization, consequently on the defects structure of Cu-doped LiTaO3. In other hand, the proposed vacancy models investigated by our theoretical approach are able to describe the defect structure and the substitution mechanism in each solid solutions of Cu-doped lithium tantalate.
Structural and optical characterization of sprayed Mg and Ni co-doped CdS thin films for photovoltaic applications
Authors: Garmim T , Soussi L , Louardi A , Monkade M , Khaidar M , Zradba A , Erguig H , Bouabdali E , Mghaioiuini R , Elmlouky A
Published: November 2020

In the present work, Mg and Ni co-doped CdS thin films are grown on glass substrates at a temperature of 400 °C through spray pyrolysis. The influence of Mg-doping on structural, morphological and optical properties of CdS:Ni thin films are examined. Mg level is changed from 0 % to 7 % for CdS: Ni samples just as Ni concentration is fixed 2 % for all CdS thin films. It is observed from the X-ray diffraction spectra that all the samples exhibit hexagonal structure of CdS thin films. The scanning electron microscopy (SEM) images showed a dense surface structure composed of crystallites whose average size increase with increasing the Mg doping. The optical transmission curves demonstrate that CdS:Ni thin films exhibit a best optical transparency in the visible range for 1 % Mg content compared to other specimens. The energy of the optical band gap tends to decrease from 2.46 to 2.40 eV with increasing Mg concentration in CdS: Ni.
Electric and dielectric behavior of carbonate intercalated CoAl-Layered Double Hydroxide (LDH) investigated by impedance spectroscopy
Authors: Bouragba F Z , Elhatimi W , Lahkale R , Moujahid E , Sabbar E
Published: November 2020

Cobalt-based layered double hydroxides (LDH) have invoked a great deal of interest in the field of energy storage due to their unique properties and low cost. Herein, carbonate intercalated CoAl-LDH was prepared in order to investigate the electrical and dielectric properties of this material. This polycrystalline sample was synthesized by the conventional co-precipitation method, characterized by PXRD, FT-IR and TGA, and analyzed by ICP. Ac impedance was measured by the complex impedance spectroscopy (CIS) method using pressed pellet sample over a frequency range of (1Hz-1MHz) and room temperature, to separate contribution of grains and grain boundaries to capacitance, resistance and conductivity of the sample. The adjustment of conductivity parameters by the double power law allowed the determination of σ
dc. The relaxation mechanism is dominated by long range movement of charge carriers: carbonate ions and H+ protons of water molecules in the interlayer space. This material exhibits high dielectric constant values and a low loss factor at high frequencies which makes the valorization of this material may be interesting in the area of dielectrics.
Optical properties of Red pigment for Dye Sensitized Solar Cells
Authors: Anoua Rania , Touhtouh Samira , Jouad Mohamed El , Hajjaji Abdelowahed , Bakasse Mina , Płociennik Przemysław , Zawadzka Anna
Published: November 2020

This work contains a description of the optical properties of Lithol Bordeaux dye thin films. The main use of this dye is for Dye Sensitized Solar Cells (DSSCs). Hence the need to deposit this dye as a thin layer in order to know its optical properties. The films were successfully grown by physical vapor deposition (PVD) technique in a high vacuum on transparent (glass) kept at room temperature during the deposition process. Optical properties were investigated by transmittance and photoluminescence measurements. Strong luminescence was observed around 1,68×107 CPS and a reaching an absorbance band about 100 nm in the visible range.
Oriented Membrane Processes For Extraction Of Methylene Blue And Blue P3R Dyes Across Polymer Inclusion Membranes Containing Chitin As New Extractive Agent
Authors: Chaouqi Y. , Ouchn R. , El Bouchti M. , Cherkaoui O. , Hlaibi M.
Published: November 2020

In the present work, according to the phase inversion technique, we have developed polymer inclusion membranes (PIMs) based on polymer supports polyvinylidene fluoride (PVDF) and polyvinyl pyrrolidone (PVP), with chitin as extractive agent (EA). These PIMs have been used to study the facilitated extraction and recovery of the Methylene Blue (MB) and Blue P3R dyes from simulated aqueous textile solutions. FT-IR spectra and SEM micrographs of these membranes were recorded to explore composition, structure and morphology of the elaborated PIMs. The adoption of the kinetic and thermodynamic models based on the Fick's laws, and the saturation law of the EA by the substrate (dyes) were tested to explain the performance of each membrane and the mechanism of the studied process for the recovery of dyes from water. The overall data indicate that the used extractive agent is effective for this oriented process, and the adopted membranes can remove about 87% of dyes from wastewater, without applying any external pressure on the polluted aqueous medium.
Synthesis And Characterization Of Nickel-Molybdenum Catalysts Supported On Copper Orthophosphates
Authors: Mbarka Ouchabi , Mohammed Baalala , Abdelkrim Elaissi , Mohammed Bensitel
Published: November 2020

Synthesis of a pure copper orthophosphate (CuP) prepared by Coprecipitation, and CuP modified by impregnation of NiMo (2-14 wt % of Ni-Mo oxide) have been carried out. The solids obtained were investigated as synthesized or after calcination by various physico-chemical techniques such as X-Ray Diffraction (XRD), Infrared Spectroscopy (IR), Thermogravimetric analysis (TGA), and differential thermal analysis (DTA). The results revealed that the solids NiMo/CuP consisted of copper orthophosphate Cu3(PO4)2 as major phases, together with NiMoO4 as minor phase. The diffraction lines of NiMoO4 increase by increasing the nickel-molybdenum content.
Piezoelectric β-polymorph enhancement in graphene oxide -PLA nanocomposite films
Authors: Oumghar K. , Chakhchaoui N. , Farhan R. , Eddiai A. , Meddad M. , Cherkaoui O. , Mazroui M. , Langenhove Lieva Van
Published: November 2020

The flexible piezoelectric nanocomposite films have attracted considerable interest for use in autonomous nanosystems, sensors and portable electronics. The effect of graphene oxide (GO) nanoparticles on the crystal structure, unique crystallization, mechanical behavior and significant improvement in piezoelectricity of polylactic acid (PLA) has been reported. Polylactic acid / graphene oxide (PLA/GO) nanocomposite films were prepared by the solvent casting technique using different percentages of GO. The different samples were characterized by Polarized optical microscope (POM), Fourier transformed infrared (FTIR) and X-ray diffraction analysis. The presence of β phase in nanocomposites and the enhancement of their piezoelectric properties were confirmed by FTIR and XRD analysis. These electroactive and biodegradable polymer nanocomposite thin films may be a potential candidate for the piezoelectric nanogenerators, energy storage devices and energy harvesting applications.
Growth and Characterization of CZTS Thin Films Synthetized by Electrodeposition Method for Photovoltaic Applications
Authors: Ziti Ahmed , Hartiti Bouchaib , Labrim Hicham , Fadili Salah , Batan Abdelkrim , Ridah Abderraouf , Thevenin Philippe
Published: November 2020

In the present work we deposited CZTS absorber material using a one-step electrodeposition method on ITO glass substrates. We studied the effect of sulfurization temperature on structural, morphological and optical properties of CZTS thin films sulfurized in N2+H2S atmosphere at 350, 375, 400 and 425°C for 10 min respectively for 10 min. The films have been charaterized by different techniques including X-ray diffractometer (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and UV-visible-NIR spectrophotometer. XRD patterns indicated kesterite CZTS with preferential orientation along (112) plane, the intensity of peaks increased with increase of sulfurization temperature signified the amelioration of the crystallinity with sulfurization temperature increased, the estimated crystallite size are in the range of 14.27-37.32 nm. Raman scattering experiments confirmed the presence of CZTS thin films by the characteristic peak at 336 cm−1. SEM images showed the morphology of CZTS thin films improved with increasing of sulfurization temperature. UV-Visible-NIR spectrophotometer showed that the values of optical absorption coefficient are larger than 104 cm−1 and optical band gap energy of CZTS thin films decreased with increasing of sulfurization temperature ranging 1.56 and 1.66 eV. These results make the electrodeposited CZTS films a suitable material as absorber material in solar cells applications based thin films.
First Au monolayer formation on Cu(110) surface
Authors: Sbiaai K. , Dardouri M. , Fathi A. , Arbaoui A. , Hassani A. , Eddiai F. , El Azrak A. , Hasnaoui A. , Boughaleb Y.
Published: November 2020

We study in this work the growth of a gold monolayer on a Cu (110) surface thanks to the kinetic Monte Carlo method. We considered a coverage of 0.1% of the monolayer. Indeed, the growth of a monolayer is done through the intermediary of several diffusion processes. All activation energies for each process were calculated using the static method coupled with the KMC method. This coupling is established by the ABBM anisotropic bond breaking model. The study of the results obtained in the temperature range (100-300K) at different deposition rates shows the formation of small 1D islands and certain 2D islands at high temperature (280 k-300 K).
Experimental investigation on reinforced concrete beams by honeycomb sandwich panel structures: mechanical properties study
Authors: Essaadaoui K , Ait El Fqih M , Idiri M , Boubeker B
Published: November 2020

In this work, the results of an experimental investigation on reinforced concrete by fiberglass honeycomb sandwich panel structures are presented. The experimental program included three beam specimens. Two of the beams were reinforced with different thicknesses of honeycomb structures. Flexural and uniaxial compression tests were performed. The tensile strength remains to be increases by a factor of 2.40 for compression and by 1.60 for flexion. The results obtained in terms of reinforcement are discussed. The changes are likely attributed to a modification of the adhesion forces at the honeycomb structures/concrete interface.
Correlation and diffusion breaking in the failure process of composite materials
Authors: Hader A. , Sbiaai H. , Tanasehte M. , Bakir R. , Boughaleb Y.
Published: November 2020

Fiber bundle model is one of the important statistical and theoretical physics approaches to investigate the fracture and breakdown of heterogeneous material extensively used both by the engineering and physics community. In this paper, using the correlation function and its properties, we study the diffusion of the failure process in composite materials that consist of a set of with randomly oriented fibers loaded by an external constant total load. The investigation is based on fiber bundle model where the fibers are randomly oriented; each fiber is subject only the cosine component of the external load, and when it fails, its load is shared by surviving neighboring fibers according to the local load sharing rule (LLS). The failure process ensures an advancing interfacial fracture and the areas of the damaged regions increases with time until a final crack of material. By using the correlation function of the fraction of broken fibers, we study the diffusion properties of micro crack created in the composite materials. The results show that the correlation decreases exponentially with time and decreases with both of applied load and temperature. We calculate then the effective diffusion coefficient cracks which increase exponentially with applied load and linearly with the temperature. The failure timetfof the materials decrease with temperature as a power law. Obtained results are compared with the one of the classical model consist of a set of parallel fibers.
Modeling of crack diffusion in composite materials
Authors: Achik I. , Hader A. , Sbiaai H. , Boufass S. , Tanasehte M. , Boughaleb Y
Published: November 2020

Our aim is to investigate the crack diffusion created at single region of composite materials by using the fiber bundle model. So, we have applied an external single crack in one fiber of the composite material, and we then continue to increase this load at a very slow rate until the considered fiber breaks and its load is redistributed to its neighboring intact ones. This breaking and redistribution dynamics repeat itself and this process ensures an advancing interfacial fracture and the area of the damaged region increases with time until a final crack of material. Our calculations are done in the context of the local load-sharing rule. The results show that the damaged region area increases with time by following the Lifshitz-Slyozof law with an exponent growth x=2. This permits us to deduce the behavior of the crack diffusion with the applied load. The corresponding results of the life time materials exhibit an exponential decreasing with the applied load and a linear decreasing with temperature.
Prediction of Mechanical Performance of Natural Fibers Polypropylene Composites: a Comparison Study
Authors: Rouway M. , Nachtane M. , Tarfaoui M. , Chakhchaoui N. , Omari LH. , Fraija F. , Cherkaoui O.
Published: November 2020

The future trends of wind turbine blade materials are mostly centered around utilizing lighter materials with improved life cycle and low cost. In modern wind turbine blade, using green composite or biocomposite is a sustainable solution, especially for small wind turbine blade with natural fiber and biodegradable polymer. In this work, four natural fibers (Alfa, Flax, Sisal and Hemp) are used with Polypropylene (PP) thermoplastic polymer. The objective is to evaluate the elastic muduli of composite by two methods; Analytical Mori Tanaka theory and numerical with Digimat MF. The results show a good validation between the two methods. The comparison of the mechanical behaviour of the transversely isotropic of natural fibers indicate that the hemp have a good performance with high Young and shear modulus regarding to their low density, which can offer an excellent candidate for the manufacturing of small wind turbine blades in rural and isolated areas.
The effect of fibers-matrix interaction on the composite materials elongation
Authors: Tanasehte M , Hader A , Sbiaai H , Achik I , Boughaleb Y
Published: November 2020

Failure process in composite materials is the basis of various actual researches. It study is the almost treated with fiber bundle model (FBM), in the framework of local load sharing rule (LLS), were the breakdown mechanisms is controlled by different parameters. Almost tentative investigates only fiber failure process and neglects the effect of the matrix, as a second crucial component of composite. Effectively, quantification of fibers-matrix interactions is not generally clear. Furthermore, the diversity of composite intrinsic proprieties complicates this quantification. The originality of our investigations is to quantify all interactions between fibers and matrix in a single parameter. Likewise, this latter gives us a different results than the ones obtained with FBM where the interaction amplitude is neglected. Moreover, interaction decelerates the failure process; it subdivides the avalanche phenomena on two consecutive regimes separated by delaying duration. These results are more similar to the ones obtained regular fibers substations. Therefore any fiber have its own elongation, the mean fiber elongation produces an elastic energy. The temporal variation of these latter presents two extremum separated by time duration; at this separated period, the material self-rearranging. These results are more similar to the ones obtained by the regular fibers substitution process.
The study of the relationship between stock value and financial performance of iron and steel enterprises using artificial intelligence techniques
Authors: Potanin V V , Sidorov O Yu
Published: November 2020

Study of the relationship between finance performance and market equity value of Russian public companies, such as PJSC Mechel, PJSC Novolipetsk Iron and Steel Works, PJSC Magnitogorsk Iron and Steel Works, PJSC Severstal using the artificial neural network (ANN) has been carried out. Data of annual financial statements, stock-exchange equity prices, USD/RUB, EUR/USD exchange rates, RF CB base rate were used as initial data. The number of instructional examples was equal to 15 and there were 16 input values included into each example. In the end, ANN calculated the ratio of the market value of one share to equity capital per share. ANN training was carried out using the backpropagation method and the conjugate gradient method. The average values of discrepancies between the actual value of the ratio of market value to equity capital and calculated value using ANN were 6.0, 2.5, 8.2 % for NLMK, Severstal and MMK, respectively. The use of ANN has shown the overestimated value of equity stock-exchange quotations of PJSC Mechel in relation to the market averages.
Comparative evaluation of effectiveness indexes of column packings in benzol absorbers
Authors: Nogovitsyna E V
Published: November 2020

Coke-oven gas is produced during coking of charge coal in a coking chamber and it constitutes a mix of different substances. A composition of different components in the gas depends on a composition of the coal charge and conditions of the coking. At a recovery plant, aromatic hydrocarbons are retrieved from the coking gas by absorption oil in packed absorbers. Mass-transfer apparatus demand the equability of the phase distribution. Hydrodynamic conditions, appearing inside contacting apparatus, determinate the effectiveness of the mass-transfer, which means that unbiased evaluation of any given mass-transfer apparatus can be made while simultaneous considering its hydrodynamic and mass-transfer indicators. The different types of column packing have been investigated in this study. The calculations of benzol absorbers have been performed basing on the initial data using the standard methodologies for the recovery plant of JSC EVRAZ NTMK coke and by-product enterprise. For comparison of the results obtained, the complex indexes of effectiveness, that simultaneously take into account the mass-transfer rate, the device capacity, the features of packings and energy cost, have been used.
Substantiation of parameters of underground geotechnology in the development of complex structural deposit of various grades of ores
Authors: Mazhitov A M , Volkov P V
Published: November 2020

Analysis of mining production activities at the current stage of field development shows an acute deficit in mineral raw materials. At present, most enterprises have exhausted all their prospective reserves and inevitably return to the reserve. Such sites have as a rule a low content of the useful component, are composed of different-grade ores and are located in difficult mining and geological and technical conditions. Their development requires significant capital investment and accordingly this leads to a decrease in the profitability of production. In order to maintain production capacity and extend the life of the field, companies are forced to ensure their development, despite a decrease in overall profits. The search for possible technologies for mining these areas of deposits is an urgent and priority direction for many enterprises. So, in the presented report are the optimal variants of the development of deposits shown, it is represented by different-grade ore bodies, most of them are stacked off-balance ores. The presented solutions make it possible to increase the life of the enterprise by increasing the reserves of previously substandard ores.
Counterflow step-type bulk material cooler
Authors: Shishkin A S , Shishkin S F
Published: November 2020

Counterflow cooling is extensively used in many industries to recover the heat from hot materials coming out of kiln. The method for calculating a counterflow step-type bulk material cooler is proposed. It is based on a matrix model of heat balance for individual cooling stages. The proposed equation system allows calculating the required number of steps and airing flow rate. The method was used to design a cyclone heat exchanger for an alumina calcination furnace and a counterflow louvered proppant cooler. It allows taking into account the degree of heat transfer incompleteness at individual stages and minimizing air flow for cooling. Examples of industrial introduction are given. The applicability of the method for counterflow heaters calculating is noted. On the basis of the offered method, step counterflow coolers with louvers were developed and introduced. Such devices and calculation methods can be used to heat the material before being fed into the furnace. The use of step-type counterflow heat exchanger makes it possible to utilize the heat of bulk material leaving the furnace and the heat of exhaust gases.
Calculation of a closed grinding cycle in a jet mill with two classifiers
Authors: Barakovskikh D S , Shishkin S F
Published: November 2020

The matrix calculation method is successfully used for calculating the closed cycle in a jet mill. In the traditional closed-cycle scheme of a jet mill, a dynamic centrifugal classifier is used for fine separation of the grinding product. The circulation load can be up to 5 or more. This involves using a high-performance classifier the cost of which will be a significant share of the total installation cost. In addition, the dynamic classifier rotor wear is proportional to the quantity of material, i.e. performance. To eliminate these shortcomings a closed loop scheme with two consecutive classifiers is proposed within the framework of the matrix model. Moreover, the first classifier must be of the pass-through type and the second is of the dynamic one. The use of this scheme in mica production allowed reducing the circulation load on the second centrifugal dynamic classifier for fine separation of the material by two times. Equations that allow determining the granulometric composition and mass yield of separation products, the multiplicity of circulation, the load on the mill and classifiers are obtained. The mathematical model proposed permits to calculate the optimal separation limits of each classifier.
Nickel sorption from solutions with high salt concentration
Authors: Makovskaya O Yu , Kolmachikhina O B , Lobanov V G , Polygalov S E
Published: November 2020

The object of the study is salt concentrates formed as a result of treatment of concentrated acidic and alkaline wastewater of galvanic processes, realized on Ural Optical & Mechanical Plant (Russia). Salt concentrates are to be disposed of as low-hazard substances, but periodically the presence of nickel ions in them was detected. Concentration of nickel ions reaches up to 0.3 g/L, the total salt content reaches 200 g/L. The possibility of sorption purification of salt concentrates from nickel on the aminocarboxylicionite Lewatit TP 207 was studied, and the capacitance characteristics of the ionite were determined. It is shown that a high salt background does not reduce the ion exchange capacity of ionite for nickel. The dynamic capacity of Lewatit TP 207 before the breakthrough was 0.155 g/g. Nickel desorption is carried out with 20% sulfuric acid. The maximum concentration of nickel in the eluates was 25.484 g/L. Such eluates can be returned to the nickel-plating bath. The technology of periodic ion-exchange purification of salt concentrates is proposed.
Technology for carrying out hydraulic fracturing using a new material ‘nitinol’
Authors: Verisokin A E , Yanukyan A P , Serdyukov D Yu , Zhulina L G
Published: November 2020

The paper examines the causes of proppant backflow from a fracture to a well, and presents the main technologies for proppant control. The consequences of the removal of the fracture filler into the wellbore are determined. It has been noted that proppant backflow is most damaging to wells operated by electric centrifugal pumps. Existing methods of hydraulic fracturing are investigated, their disadvantages are indicated. A method has been developed for hydraulic fracturing with injection of compressed springs made of metal with the effect of ‘memory’ and restoring their shape under reservoir temperature stress. In the first stage, the remote section of the crack is filled with a fine fraction of ceramic proppant, and at the final stage of crack attachment, compressed springs made of nitinol material are fed. Using of material with a shape memory will allow the proppant packing to be compacted and the proppant to be ‘locked’ in the fracture.
Analysis of single- and double-threaded rolling for production of grinding balls of alloy steel grades
Authors: Galimyanov I
Published: November 2020

JSC EVRAZ NTMK has mastered the technology of production of grinding balls with high hardness of surface and normalized hardness at the depth of 0.5 of a ball radius (4th hardness group) and normalized volume hardness (5th grade hardness) in accordance with Russian state standard GOST 7524–2015. Currently rolling of balls with the rated diameter of 100 mm is performed using double-threaded rolls. Single-threaded pass design is used for rolling of the 120-mm grinding balls. Double-threaded pass design increases a feed angle of rolls. The higher angle increases tangential stresses. 100-mm balls produced through the double-threaded pass design where the flanges excessively wear, show specific defects on a surface of the balls. This article describes the materials and results of the study of rolling of the grinding balls with the diameter of 100 mm and 120 mm produced via single- and double-threaded designs. Lower tangential loads applied to the balls during single-threaded rolling affects their macro structure, their hardening layer thickness.
Study of possibility of cerium reduction from slags of CaO-SiO2-Ce2O3–15%Al2O3–8%MgO system
Authors: Babenko A A , Smirnov L A , Upolovnikova A G , Shartdinov R R
Published: November 2020

By means of theoretical and experimental studies it is shown that it is possible to reduction cerium from the slags of the CaO–SiO2–Ce2O3 system containing 15%Al2O3 and 8 % MgO, by aluminum dissolved in metal, at temperatures of 1550 and 1650°C. The results of mathematical modeling are presented graphically as ‘composition – equilibrium content of cerium in metal’ diagrams. It is found that depending on temperature of metal, basicity of slag and the content of cerium oxide, from 0.055 to 16 ppm cerium passes into metal containing 0.06 % of carbon, 0.25 % of silicon and 0.055 % of aluminium. Positive influence of the temperature factor, basicity of slags and the content of cerium oxide in a studied range of chemical composition on process of cerium reduction is explained from the perspective of phase structure of formed slags and thermodynamics of reactions of cerium reduction. The possibility of reduction of cerium from slags of CaO–SiO2–Ce2O3 system, containing 15 % Al2O3 and 8 % MgO, has been experimentally confirmed. It has been shown that at basicity of 5 and 4 % of Ce2O3 in slag up to 16 ppm cerium passes into metal during 10 minutes exposure.
Destruction electrospark deposits during Joule heating of base metal
Authors: Trekin G E , Shevchenko O I
Published: November 2020

Electrospark coating deposited on the surfaces of machine parts is a common surface hardening method. Hard materials are normally used for depositing to improve wear resistance or other properties. In this investigation electrospark deposition intended for use as micro-alloying of welds by deposition on to the surface of the base metal and in this case it remelts completely. Intense heating and destruction occurs before remelting, which changes the chemical composition of the melt. The aluminum and titanium coatings is shown to deteriorate at 500 to 650 °C generating a liquid phase due to eutectic available in both metals in this temperature range. Most of titanium and aluminum oxidized at that. It is found that a solid layer, appears after electrospark depositing using both coatings. For aluminum coating, after high-temperature heating, a thicker white layer appears with the same microhardness level as that of the base metal, and a thin layer of partial decarburizing. Fusion sectors are detected in the titanium coating that are harder than the base metal and have a dendritic structure, followed by a thin zone of complete decarburization and quite an extended zone of partial decarburization.
Effect of basicity and chromium oxide on the viscosity of boron-containing slags
Authors: Babenko A A , Shartdinov R R , Upolovnikova A G , Smetannikov A N , Mikhailova L Yu
Published: November 2020

The main diluent for chromium-containing slags is CaF2. However, fluorspar disadvantages make it necessary to search for a replacement. As a substitute, boron oxide allows to improve slag physical properties and environmental situation. The paper presents the experimental study results of the chemical composition and temperature influence on viscosity of slags of CaO–SiO2–Cr2O3 system containing 8% MgO, 3% Al2O3 and 6% B2O3. It was found that a slag free of chromium oxide with basicity of 1.0 has a sufficiently high fluidity of 0.2–0.6 Pa·s in a wide temperature range of 1200–1350°C, due to high concentration of low-melting phases, reaching 22%, and only 11 % high-melting. A slag with 18% Cr2O3 and the same basicity retains a low viscosity of 0.1–1.0 Pa·s but at higher temperature of 1450–1570 °C due to increase in high-melting compound content to 27%. The viscosity of a slag with basicity of 2.5 without chromium oxide is 0.07–1.0 Pa·s in a narrow temperature range of 1650–1700°C and 0.14–1.0 Pa·s for a ‘shorter’ slag with 18% Cr2O3 and same basicity in even narrower range of 1650–1670°C. These slags have the highest high-melting phase content of about 50%.
The use of additional filler wire to solve the tandem GMAW issues
Authors: Polevoy I O , Fiveyskii A M
Published: November 2020

A review of the studies showed that the existing technologies for tandem gas metal arc welding (GMAW) of butt welds have a number of problems that do not allow to increase productivity while maintaining low heat inputto base material and stability of the welding process. The possible solution of this problem by feeding of additional filler wire (AFW) in between the welding electrodes is researched in this study. Influence of addition of AFW into the arc and into the weld pool for single-arc GMAW on deposition rate and geometric properties of the welds are researched and the main problems of these methods are showed in the study. The effect of addition of AFW on the temperature of weld pool and heat input to base metal and solidification rate of the weld pool are showed in the study too. The main disadvantages of using pulsed welding modes for providing the stability of tandem welding process are described and the addition of AFW in between the welding electrodes for stabilization of trailing arc is justified. It is concluded that the further complex studies of effects of AFW on tandem GMAW are needed.
Double-sided arc welding with multiple electrodes of vertical joints of steel tanks
Authors: Filippov O I , Erofeev V A , Poloskov S I , Melnikov A Yu
Published: November 2020

The increase of the welding productivity is still of immediate interest, which in turn requires the development and implementation of more high-performance welding methods that ensure a consistently high quality of welded joints. One of the ways to further increase the productivity of arc welding processes in the construction of tanks is the industrial use of automatic double-sided arc welding with multiple electrodes in separate weld pools. To establish the relationship between the parameters of the welding mode, energy characteristics, as well as the distance between the torches and their angle of inclination relative to the groove, a physical and mathematical model of the production of the welding joint when four arcs participate in pairs from both sides of the joint has been developed. Thus, computer modeling showed that during weld formation with the movement of the electrode down (vertical down), the possibility of supplying each pair of arcs with pulsed current should be taken into account. During groove filling with the movement of the electrodes up (vertical up), their lateral oscillations and delays at the edges should be carried out according to an aperiodic law in order to minimize the effects of ‘magnetic blow’.
Application of surfacing using consumable electrode with an additional filler wire to ensure the required operational properties of pipeline valves
Authors: Poloskov S S , Buzorina D S , Erofeev V A
Published: November 2020

A promising way to ensure the required operational properties of pipeline valves with a significant increase in productivity and quality of surfacing during its manufacture is the introduction of anti-corrosion surfacing technologies using a consumable electrode with the supply of an additional filler wire. A solution to the optimization problem of the proposed surfacing technology is complicated by a large number of its parameters, therefor the task was solved in stages. At the first stage, the parameters of the arc interaction between the electrode and filler wire was determined, and at the second – the specific features of the formation of the surfacing bath with such interaction. A virtual study of the process of surfacing with Inconel 625 wires in argon on steel 09G2S was carried out. The influence of the thermal effect of the deposition mode parameters on the main metal is determined. It has been established that, due to the fact that the heat flux in the main metal is created mainly by the droplet stream of the deposited metal from the main arc at high currents, the diameter of the electrode wire guaranteeing its burning should be larger than the filler wire.
Influence of technological parameters on the vanadium valence form in slags
Authors: Klimov A V
Published: November 2020

The multivalence of vanadium in oxide melts is considered. It is shown that the vanadium oxidation state in the slags is determined by the slag and metal compositions as well as the oxidation potential of the gas phase. Using a polymer model, vanadium valence form fractions were calculated depending on technological parameters. Calculations show that in an air atmosphere, vanadium in the slag should be predominantly in the tetravalent and trivalent state, and in contact with the molten iron, mainly in the trivalent and partly divalent state. Upon contact with pig iron, VO oxide becomes the main form of vanadium in the slag. Slag basicity and temperature have a significant effect on the relationship of vanadium forms. The suggested design-basis using the polymer model can be useful in accomplishment of the thermodynamic calculations for the vanadium equilibrium distribution between metal and slag in the iron and steel production. It allows us to describe the dependence of the vanadium oxidation state on the free oxygen activity in the slag and the gas phase oxidation potential.
Technology for fixing mine workings with friction anchors of the SZA type with a new type of anticorrosive coating
Authors: Volkov P V , Kulsaitov R V , Magitov A M
Published: November 2020

The issues of ensuring the stability of mine workings in weak rocks due to the use of combined roof support based on anchors with a new type of anti-corrosion coating on the example of mining enterprises of the Russian Federation are considered. As a result of the work, the quality indicators of man-made mine waters of mining enterprises of the Russian Federation were determined, the conditions of the mine atmosphere that contribute to the intensification of metal corrosion were identified, an experiment was conducted in the research laboratory to determine the corrosion resistance of self-fixing anchors, the most suitable anchor coatings for their use in aggressive mine environments were identified, The technology of fixing with anchors with a new type of anti-corrosion coating is proposed. Also shown are the conditions for the use of galvanized, paint and varnish coatings, as well as various protective materials, the scope of their application, the advantages, and disadvantages of these coatings in mine environments are indicated. The prospects for the use of new types of coating are shown and directions for further research in this direction are indicated.
Application of hydrohammers of heavy class in the development of marble deposits in mining operations
Authors: Pytalev I A , Domozhirov D V , Ugolnikov N V , Prochorov A A
Published: November 2020

By development marble deposits in mining operations one of the main technological processes, that ensures minimal losses and dilution with maximum output of commercial products is the process of preparing rocks for excavation. Marble extracted for the production of microcalcite is prepared for excavation by drilling and blasting at most mining enterprises. This inevitably leads to overgrinding in the charging chamber zone and, as a result, to a decreasing in quality indicators (yellowness and whiteness), significant losses of minerals (0–20 mm fraction) up to 30% and a low percentage of high-grade crushed stone in the commodity balance. The paper considers a variant of improving the production technology on the example of the Eleninsky marble Deposit (Chelyabinsk region) by using of heavy-class hydrohammers, which allows to increase the efficiency and completeness of the development of balance reserves by reducing by 5–10% overgrinding and increasing output of a commercial product high grades (40–200 mm).
The microstructure and hardness of casting a solid brake disc after late graphitizing modification
Authors: Boldyrev D A , Dema R R , Kalugina O B
Published: November 2020

The features of graphite formation in hypoeutectic and hypereutectic gray cast iron are considered. It is shown that this process in hypoeutectic gray cast irons is easier to control than in hypereutectic, because the formation of a predominantly rectilinear uniformly distributed graphite with a smaller size range and the presence of other distributions is achieved by an one-stage operation of ladle graphitization. The structure of graphite in hypereutectic gray cast irons is characterized by a large variety of its shapes, sizes and distributions, and it is also less technologically stable and controllable. Its characteristics can be approximated to the structure of hypoeutectic gray cast iron due to the obligatory second stage of graphitization. The microstructure and hardness of casting a solid brake disc after late graphitizing modification in a mold are investigated. The content of interdendritic distributions of graphite PGr8, PGr9 and short inclusions of graphite PGd45-90 (GOST 3443-87) was minimized due to the operation of the secondary (late) graphitizing modification. And Brinell hardness of the solid brake disc meets production requirements.