bluuebunny/crossref_metadata_2025 huggingface dataset:
Processing of myoelectric signals in a microcomputer for identification of movements intention and the cost reduction in the purchase of prosthesis in Peru
Authors: Chávez Eduardo , Sifuentes Billy , Chauca Ricardo Vidaland Mario
Published: February 2021

In the present document a processing technique is applied to identify the intention of movement in the myoelectric signals, by means of algorithms entered in a microcomputer with a software of free programming that presents a great speed when executing the instructions, with the necessary resources, to replace the PC and thus achieve low costs while maintaining the high quality standard, making the system accessible and reliable for people with low economic resources, while generating greater portability compared to the current prostheses that are handled in Peru, that are mostly made abroad, which increases the cost
Redesign website of engineering faculty in university of Indonesia using fuzzy delphi method and fuzzy cognitive maps
Authors: Suzianti Amalia , Mualim Agasi , Danisworo Ademas Muhammad
Published: February 2021

Utilizing website in business process has become essential. But lot of web designer have no respect of using methodology in developing a website cause the quality that website do not meet the needs of its users. On the other hand, usability level of the website could not attract a lot of visitation from any user. On this paper, researcher using Engineering Faculty in University of Indonesia’s website to be studied. To increase the usability of this website, research conducted by redesign the website using Fuzzy Delphi Method to determine the media type to presenting each service and also to determine the services layout of each web page. In addition, this research also uses Fuzzy Cognitive Maps to models the interrelationship between each services and media type. Resulting the prototype of 12 web page for website owned by Engineering Faculty in University of Indonesia with total 36 services provided in this website to gives an optimal information for the user.
Prediction of genetically-evaluated tumour responses to chemotherapy from breast MRI using machine learning with model selection
Authors: Yuan Taiguang , Jin Ze , Tokuda Yukiko , Naoi Yasuto , Tomiyama Noriyuki , Obi Takashi , Suzuki Kenji
Published: February 2021

Genetic tests can provide prognostic information in breast cancer for both diagnosis and treatment planning. However, the cost of a genetic test is still high. In this study, we developed a radiogenomics method to predict genetically-evaluated responses to chemotherapy for breast cancer using our machine-learning technology coupled with model selection. Our proposed method consists of feature extraction, model selection, and prediction by the selected model. In the feature extraction, 318 morphological and texture features were extracted from a tumour region. In the model selection module, there are two major components: (1) selection of imaging biomarkers based on our original sequential forward floating selection (SFFS) feature selection and (2) building of a support vector machine (SVM) classifier including kernel function selection and hyperparameter optimization. The optimized feature set, i.e. imaging biomarkers, coupled with an SVM classifier were chosen by maximizing the area under curve (AUC) of corresponding receiver-operating-characteristic curve (ROC). After the model selection, the optimized SVM classifier operated on the selected imaging biomarkers for prediction. We applied our proposed method to 118 breast MRI studies from 118 patients for predicting genetically-evaluated responses to chemotherapy for breast cancer that evaluated by the genetic test of IRSN-23. We achieved an AUC value of 0.96 using the optimized SVM classifier model coupled with 24 selected imaging biomarkers in predicting the results of IRSN-23 in a five-fold cross-validation procedure.
Implementation of PROMETHEE Method for Employee Performance Assessment System
Authors: Zulita Leni Natalia , Diansyah Tengku Mohd , Aulia Rachmat
Published: February 2021

PT Trimba Engineering is a company which turns on field of the repair and maintenance modules for various telecommunications devices and transmissions to aviation navigation systems. The firms, does an annual audit to assess employees performance that the outcomes of their performance will determine whether they acquire an annual bonus or not. Performance assessment is divided by five achievement categories which are Special, Excellent, Good, Enough, and Poor. But, those who get a bonus, if the outcomes of the performance assessment obtained is Special (two time salary), Excellent (one time salary), and Good (half salary). The performance assessment over five that achievement categories, still have any error in manage of its data. There is no ranking for outcomes of performance assessment obtained. And, it only focuses on the first criteria, but the employee is not necessarily excellent to several other criteria. In this research, the assessment uses a Promethee method, which it done based on three criteria such as technical performance, task execution, and personality. Each criterion has twenty one sub-criteria. The final result according to employee assessment performance obtains by using Promethee with comparize between an alternative with others, then looking for a deviation in order to compute a value of leaving flow, entering flow, and net.
Rainbow Coloring of Three New Graph Classes
Authors: Fredlina Ketut Queena , Salman A.N.M. , Julihara I Gede Putu Krisna , Werthi Komang Tri , Astawa Ni Luh Putu Ning Septyarini Putri
Published: February 2021

Let G be a simple, finite, and connected graph. A path in an edge colored graph is said a rainbow path, if no two edges on the path have the same color. The graph G is called a rainbow-connected, if any two vertices are connected by a rainbow path. An edge-coloring of such G is rainbow coloring. The rainbow connection number rc(G) of G is the smallest number of colors needed in order to make G rainbow connected. In this paper, we introduce three new graph classes, namely tunjung graphs, sandat graphs, and jempiring graphs. We determine the rainbow connection number of the graphs.
Detection of lung cancer with electronic nose using a novel ensemble learning framework
Authors: Liu Lei , Li Wang , He ZiChun , Chen Weimin , Liu Hongying , Chen Ke , Pi Xitian
Published: February 2021

Breath analysis based on electronic nose (e-nose) is a promising new technology for the detection of lung cancer that is non-invasive, simple to operate and cost-effective. Lung cancer screening by e-nose relies on predictive models established using machine learning methods. However, using only a single machine learning method to detect lung cancer has some disadvantages, including low detection accuracy and high false negative rate. To address these problems, groups of individual learning models with excellent performance were selected from classic models, including support vector machine, decision tree, random forest, logistic regression and K-nearest neighbor regression, to build an ensemble learning framework (PCA-SVE). The output result of the PCA-SVE framework was obtained by voting. To test this approach, we analyzed 214 breath samples measured by e-nose with 11 gas sensors of four types using the proposed PCA-SVE framework. Experimental results indicated that the accuracy, sensitivity, and specificity of the proposed framework were 95.75%, 94.78%, and 96.96%, respectively. This framework overcomes the disadvantages of a single model, thereby providing an improved, practical alternative for exhaled breath analysis by e-nose.
3D printing. An alternative for small projects?
Authors: Mihalache A M , Nagit G , Ripanu M I , Slatineanu L
Published: February 2021

3D printing is one of the big top up-to-date technologies. Our aim is to show that up to a point 3D prints can successfully replace traditionally manufactured assemblies in the case of educational projects or lab experiments. We have considered a 3D printed simple-frame robotic arm upon which we have performed FEA analyses. They have shown promising results against its steel-based peer up to certain loads under the same working conditions in terms of safety factor and safety margin.
On machining Ti6Al4V ELI with EDM by using copper and graphite electrodes: a comparison study
Authors: Karmiris-Obratański P. , Zagórski K. , Papazoglou E.L. , Karkalos N.E. , Markopoulos A.P.
Published: February 2021

Electrical Discharge Machining (EDM) is a non-conventional machining process, in which, the material removal occurs by repetitive sparks. By utilizing EDM, conductive materials can be machined in complex shapes and geometries, with high dimensional accuracy, regardless of their mechanical properties. Titanium alloys, due to their unique inherent properties, find extensive use in the modern industrial environment. Nevertheless, they are still classified as hard-to-cut materials, facing significant difficulties in their machining with conventional methods. The current paper presents a comparative study regarding the machining of Ti6Al4V ELI with EDM, by using copper and graphite electrodes. The control parameters were the pulse-on current and time, while the machining performance was estimated in terms of Material Removal Rate (MRR) and Tool Wear Ratio (TWR). Additionally, the surface roughness was evaluated according to the Ra. For the aforementioned indexes, Analysis Of Variance (ANOVA) was performed.
On the micro-modelling of surface roughness in pulsed laser machining
Authors: Kaselouris E , Orphanos Y , Kosma K , Skoulakis A , Fitilis I , Bakarezos M , Papadogiannis N , Tatarakis M , Dimitriou V
Published: February 2021

The surface roughness and the evolution of its morphology of a pulsed laser irradiated aluminum workpiece, is investigated via numerical simulations and experimental measurements. A three-dimensional transient thermo-structural finite element model is developed to simulate the machining process. The developed finite element material model considers the effects of plastic strain, strain rate and temperature, along with a fracture model. For the experiments, a single laser pulse of 6 ns duration and 0.7 mJ of energy at 532 nm is employed as the heat source, and the surface roughness is measured using white light interferometry set-up and related experimental diagnostics. A step-like linear approximation is used to model the surface roughness. A satisfactory agreement between the experimental data and the simulation results is found. This preliminary study aims to contribute to a better understanding of the initial physical processes involved in pulsed laser machining considering the influence of surface roughness and is beneficial for industrial applications such as laser polishing, engraving and cutting.
Rolling element bearings fault classification based on feature extraction from acceleration data and artificial neural networks
Authors: Kotsanidis K , Benardos P
Published: February 2021

This paper presents the development of an artificial neural network (ANN) model for rolling element bearings fault classification that uses features extracted from acceleration data collected during run-to-failure experiments. The presented approach initially employs a wavelet decomposition method for signal denoising and subsequently relies on a Fourier transform to analyse the acceleration signal in the frequency domain. Several features that correspond to the entire signal range as well as to specific frequency bands are then extracted and used as inputs in the ANN model, which is trained to identify three different operational states, namely, no fault, inner race fault and outer race fault. The developed ANN model is validated using experimental data from the publicly available dataset provided by the Center of Intelligent Maintenance Systems (IMS) of the University of Cincinnati. The results show that the trained ANN model has a classification accuracy of 90.2% in the training data and 100% in the test data.
FEM based investigation on thrust force and torque during Al7075-T6 drilling
Authors: Tzotzis Anastasios , Markopoulos Angelos P. , Karkalos Nikolaos E. , Tzetzis Dimitrios , Kyratsis Panagiotis
Published: February 2021

As modern industry advances, the demand for more time and cost effective machining is rising. In order to achieve high levels of standard during machining it is necessary to employ sophisticated techniques for precise prediction of various important parameters that relate to the machining processes. Such technique is the implementation of finite element modelling (FEM) which can become a valuable tool for researchers and industry engineers alike. In this work, the 3D modelling of Al7075-T6 drilling process with solid carbide tooling is being presented. DEFORM3D™ finite element analysis (FEA) software was utilized for simulating the drilling process based on frequently used cutting conditions; cutting speed of 100m/min and feed of 0.15mm/rev, 0.20mm/rev and 0.25mm/rev respectively. In order to approximate the complex phenomena that occur during drilling, the most critical factors were considered in the presented model such as the developed friction, heat transfer and damage interaction between the tool and the workpiece. Additionally, a validation of the generated results for thrust force and torque was performed by comparing the simulated results with experimental data. Three drilling experiments were carried out with the aid of a CNC machining center and a four component dynamometer in order to acquire the experimental values of thrust force and torque. Most of the simulations yielded results in accordance to the experimental ones with the agreement percentage reaching 95% in most cases for both the thrust force and torque, confirming the validity of the models and the accuracy of the simulated results.
Shrinkage Factor Analysis in the Dry Machining of UNS A92024 Alloy by FEM
Authors: Trujillo F J , Bermudo C , Martín-Béjar S , Svensson D , Andersson T , Sevilla L
Published: February 2021

Chip evacuation becomes a relevant factor in the dry machining of aeronautical aluminium alloys, either when they are machined as isotropic material or hybridized with other materials. Chip morphology and geometry highly depend on cutting parameters. Several works can be found in the literature focusing on the analysis of chip morphology of aluminium alloys at high cutting speeds but there is a lack of studies that apply low cutting speeds. FEM simulation may be useful to reduce the experimental time and cost of this kind of analysis. Therefore, in this work, the influence of feed-rate on several chip geometrical parameters (height of peaks, height of valleys and shrinkage factor) of dry turned UNS A92024 alloy has been analysed by FEM simulation. Three different energy fracture modes have been tested as damage evolution criterion, in order to get the mode that better fit the experimental chip morphology. In general, the mixed mode was the fracture energy mode that best suited the chip morphology behaviour, within wider feed-rate range.
Cutting parameters influence analysis on fatigue behaviour of dry turned UNS A97075 alloy after corrosion
Authors: Martín-Béjar S , Trujillo F J , Bermudo C , Herrera M , Sevilla L
Published: February 2021

Aluminum alloys, particularly series 2000 (Al-Cu) and 7000 (Al-Zn), are widely used for structural elements in aircraft. Machining processes are frequently applied in manufacturing these parts. The actual trend in the machining of these components is to reduce or eliminate the use of lubricants, due to environmental reasons. Among the different techniques, dry machining is commonly used for aluminum alloys. However, dry machining generates higher severe cutting conditions, which may negatively affect the surface integrity and the mechanical properties of the machined parts. In this regard, fatigue life is one of the most important mechanical properties to take into account. Micro-cracks generation and nucleation strongly depend on the surface conditions of the machined parts. Additionally, the addition of Zn to pure aluminum (7000 series) reduces the corrosion resistance. Despite its importance, there is a lack of research devoted to analyze the cutting parameters influence on fatigue behaviour, before and after corrosion, in dry machining of these alloys. Therefore, in this work, the cutting speed and feed rate influence on fatigue behaviour of the UNS A97075 (Al-Zn) alloy has been analyzed. Several rotating bar bending fatigue tests have been carried out, studying and comparing the fatigue life curves obtained as a function of the cutting parameters, before and after an immersion corrosion process. The experimental results have revealed that an increment in the cutting speed and feed rate gives rise to fatigue life reduction.
A case study on 3D scanning, digital reparation and rapid metal additive manufacturing of a centrifugal impeller
Authors: Kladovasilakis N , Kontodina T , Charalampous P , Kostavelis I , Tzetzis D , Tzovaras D
Published: February 2021

This paper demonstrates a comprehensive method for digital restoration and rapid manufacturing of a fully functional mechanical component. A damaged centrifugal impeller of an automotive engine was reverse-engineered via a 3D laser scanner, with which the 3D model of the investigated object was digitally captured. Utilizing advanced design software and surface modelling, the missing fragments were restored and the impeller’s 3D digital model was reconstructed. Metal additive manufacturing technology and more specifically the Selective Laser Melting (SLM) technique was employed to construct a functional metal impeller. Stainless steel 17-4 PH powder was used as the printed material. To ensure the exploited powder was appropriate for the part to be manufactured, we applied characterization of the feedstock material was conducted through two different characterization methods, i.e. granulometry and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX). Furthermore, Surface Distance Maps (SDM) were calculated to correlate the geometrical deviations between the physical 3D printed part and the digital model in order to examine the accuracy of the applied method.
Improving of preventive management for flat rolling products quality indices
Authors: Kukhar V V , Kurpe O H , Prysiazhnyi A H , Khliestova O A , Burko V A , Balalayeva E Yu , Yelistratova N Yu
Published: February 2021

Based on the combination of ISO and Lean system tools, the methodology of continuous optimization of technology and quality improvement of rolled steel has been improved. To assess the condition and determine the production level to set limits to process indices the use of colored markers was suggested. The improved flat rolling quality control methodology is based on the use of Deming cycle and includes the use of such analysis tools as Fishbone (Ishikawa) diagram, Pareto principle, distribution diagrams, 3σ rules and Shewhart control charts. For the first time, differentiated corrective solutions for plate steel which is produced with different levels of process stability and quality indices are suggested. The inspection was carried out with the data from the mechanical properties of flat steel products 14 mm thick from K60 steel, produced by thermo-mechanical controlled process on a plate mill 3600. Introduction of the methodology allowed to reduce the standard deviation of yield strength, tensile strength and percentage elongation after fracture of the studied rolled products by 44%, 31% and 46%, respectively, indicating an overall increase in technology stability and quality indices and implementation of an effective tool for their preventive control.
Validating dynamic crush response of unidirectional carbon fibre tube via finite element analysis method using LS-DYNA
Authors: Samuel R , Asadi M , Tarda A , Simbotin G , Markopoulos A P
Published: February 2021

Crashworthiness of composite structures is of significant interest to manufacturers and operators as composites become more commonly used in automobiles and aircraft. Experimental crush testing remains an important tool in the design of subfloor fuselage structures for crashworthiness, as numerical simulations are still largely unable to accurately predict the crushing response of complex composite structures. In this paper, dynamic crush testing of carbon-fibre/epoxy specimens experimental result is validated using the modelling and simulation software LS-DYNA to understand impact behaviours under dynamic loading for finite element simulations. The tubular finite element model was modelled using MAT54 and was impacted by a 65KG rigid wall impactor with an impact velocity of 55 km/h. Material card parameters were evaluated to understand crush behaviour of the FE model. Upon analysis the experimental results and the FEA results showed a good correlation. Modelling criteria used for this model can be further used to simulate crush response of unidirectional carbon tubes under dynamic impact.
Prediction of roughness of planar surfaces processed with toroidal milling through an artificial neural network
Authors: Osan A R , Banica M , Nasui V
Published: February 2021

This paper is intended to create an artificial neural network capable of generating new values for the roughness on the basis of experimentally obtained data bases. Experimentally you will measure the roughness of the flat surfaces processed with the toroidal milling, the process factors being the input neurons of the neural network, following the roughness values being the output neurons. It aims to modify the input neurons from the same neural network and generate new roughness values.
Investigation of the suitability of fiber reinforced polymer matrix composites for facilities operating in marine environment
Authors: Spasova D , Argirov Y , Mechkarova T , Atanasov N
Published: February 2021

This paper is related to the production and investigation of the structure, the mechanical and physicochemical properties of two kinds of fibre reinforced polymer matrix composites in order to assess their suitability as materials used in equipment operating in marine environment. The one of the investigated composites has a polyester resin matrix and a reinforcement phase of six-layer fibreglass, and the other one has a vinylester resin matrix and a reinforcement phase which is a combination of three-layer fibreglass and three-layer biaxial fibreglass. A comparative analysis has been made of the relative weight, tensile strength and bending strength of the two types of composite materials.
Chemical and structural analyze of experimental biodegradable ZnMgY alloy
Authors: Panaghie C , Cimpoesu R , Alexandru A , Bernevig M , Manole V , Roman A M , Prisacariu B A , Paraschiv P , Cimpoesu N
Published: February 2021

Beside biocompatible classic metallic materials, biodegradable metals (BMs) like alloys of zinc (Zn-based) present a high potential as an alternative solution for permanent implants elements generally being applied for fractures restorations or other similar medical conditions. An experimental alloy, ZnMgY, was obtained using an induction furnace from high purity materials (Zn: 99,995 and master alloy MgY: 65-35 wt%), in Argon atmosphere. Microstructure of the alloy (after mechanical grinding and polish plus chemical etching) and chemical insights (before chemical etching) were taken using optical microscope (Zeiss+Motic digital camera for image acquisition) scanning electron microscope (SEM VegaTescan LMH II, SE, 30 kV, 16 mm WD) and dispersive energy spectroscopy (EDS Bruker, PB ZAF, Automatic mode of analyze, Point and Mapping features). The experimental alloy was five times re-melted in the induction furnace using a ceramic crucible. The experimental alloys present a good chemical homogenization without porosity, metallic inclusions or segregation.
Study of the durability of ferritic - austenitic steel samples after cyclical fatigue impact
Authors: Georgiev Georgi , Argirov Yaroslav , Mechkarova Tatyana , Spasova Daniela , Stoyanova Aneliya
Published: February 2021

The purpose of this article is to investigate the fatigue strength of corrosion resistant ferritic austenitic steels used in marine equipment. Two groups of sheet steel samples were prepared: the first group were reference parts and the second group of samples were welded. The fatigue tests were performed with specially developed vibrating equipment. The destroyed surfaces were examined by optical microscopy, and the phase composition by X-ray diffraction analysis. Fatigue strength was evaluated by the number of cycles needed for a crack at a certain alternating load. Fatigue tests show how multi-cyclical fatigue affects the formation and development of a fatigue crack, and metallographic and X-ray diffraction analysis shows the phase changes occurring in the structure of SAF 2507 steel.
Characterization of metallic materials used in food packaging
Authors: Necsulescu D A , Ciurdas M , Milea C
Published: February 2021

The work represents a comparative study of three type of metallic food package used in Romanian food industry. In this paper, three food packages made of low-alloy steel were analyzed. To characterize their properties, spectrometric analyzes were performed to determine the chemical composition, microhardness analyzes, optical microscopy and Fourier Transform Infrared Spectroscopy. The investigations on the three samples were achieved through X-ray Fluorescence Spectrometry (XRF) analysis performed with a Spectro XEPOS analyzer, optical microscopy analyzes performed on a Reichert UnivaR optical microscope, and microhardness tests by the Vickers method using the CV - 400 DTS tester / 2 (CV Instruments) and Fourier Transform Infrared Spectroscopy (FTIR) with JASCO 6200 analyzer, equipped with Golden Gate type attenuated total reflection (ATR) device. Following the investigations, the presence of epoxyphenolic resin was confirmed in the case of the first two samples and a layer of polyester in the case of sample three. Finally, conclusions are presented about the qualities of the selected packaging and their properties to keep safe the packaged products for a period of several months to several years.
The potential of wave energy in the coastal region of Romania
Authors: Rus M , Mereuta E , Novetschi M
Published: February 2021

In this study, the wave energy potential in the coastal region of Romania was analyzed. For this purpose, a reanalysis data set downloaded from ECMWF (European Centre for Medium-Range Weather Forecasts) was used. The reanalysis data contains information for various models. In this analysis the significant height of combined wind waves and swell, the mean wave direction and the mean wave period were analyzed in order to determine the potential of extracting clean energy from waves. The aim of this research is to analyze some performances factors (capacity factor, rated capacity, operating capacity, annul electricity production) of some of the most used wave energy convertors.
Modelling and practical application of autocorrelation functions of vibroacoustic oscillations in a machine dynamic system
Authors: Ignatyev A A , Samoylova E M , Zakharchenko M Yu , Ignatyev S A , Dobryakov V A , Vinogradov M V , Nasad T G , Karakozova V A
Published: February 2021

The paper considers applying the residue theory in obtaining mathematical models for autocorrelation functions of vibroacoustic oscillations in a machine dynamic system during the cutting process. It shows that these models are analogous to experimental data and reflects their practical application for assessing the dynamic quality of machine tools and setting a processing mode. Calculating the dynamic system stability margin is carried out automatically according to the oscillation index obtained from a real amplitude-frequency characteristic of the dynamic system. This characteristic, in its turn, is determined from the identified transfer function. The article considers the construction of a theoretical model for the autocorrelation function of vibroacoustic oscillations of a grinding machine dynamic system, that would be equivalent to the autocorrelation function obtained from experimental data. Such a model would be feasible to use to calculate the dynamic system transfer function of the machine with a subsequent evaluation of its stability margin. It substantiates applying the dynamic system stability margin of the machine as an informative characteristic based on measuring vibroacoustic oscillations during the cutting process to evaluate the technological system quality and stating an appropriate processing mode to achieve the required part surface quality. It is shown that the identification of transfer function under the established conditions by the autocorrelation function of vibroacoustic oscillations during cutting enables us, based on the maximum stability margin of the dynamic system, to determine the machine with the highest dynamic quality and set the cutting mode, which ensures high processing quality and reduces tool wear.
The algorithm of processing and presenting the digital trajectory data obtained when launching rocket vehicles
Authors: Spitsyn S V , Potapov V I , Koryachko V P
Published: February 2021

This research aims at finding a generalized algorithm suitable for processing and presenting the trajectory digital parameters of consumer onboard navigation equipment which is used in the process of space rocket launches. Processing and analysis of digital telemetric information coming from the onboard equipment during the flight and containing digital frames of trajectory measurements is one of the priority tasks as it is the analysis of the path deviations of the rocket that makes a significant contribution to a complete and informative assessment of the launch results. It is suggested that the generalized processing and presenting algorithm which contains the initial stages of the primary processing (extraction of digital frame structures, extraction of trajectory parameters from the frames, mathematical transformations of extracted parameters)as well as determination of primary and secondary values are necessary for solving the trajectory task and, eventually, forming a unified digital stream for representing trajectory measurements, for obtaining results of processing in graphical representation software.
Combining methods for end-to-end calculation of gas flow in a Laval nozzle
Authors: Dushkov R E , Dzerzhinsky R I
Published: February 2021

The paper solves the problem of selecting optimal methods and combining them when performing a complex calculation of all sections of the Laval nozzle. The problem is significant, since different flow modes are realized in different areas of the nozzle and it is impossible to use a single method for the full calculation. Solving the direct problem, parameters in the flow of gas are determined. Solving the reverse problem determine the profile of the Laval nozzle. Profiling is an important applied task for calculating the nozzles of rocket and aircraft engines, or designing experimental turbines. In this paper, we consider a two-dimensional plane axisymmetric flow of an inviscid perfect gas (on the example of dry air). The problem is solved starting with an accelerating subsonic flow via using methods of establishing and finite elements. For subsonic flow found an exact solution (Prandtl-Mayer flow). Solving the problem in a supersonic flow via using proximate methods (the method of characteristics and interpolation for the grid normalization). The solution is supplemented by a method that allows taking into account the features of axisymmetric flow in the nozzle to expand the applicability of the solution for real nozzles. The results obtained – the gas velocity field and the coordinates of nodes. Results allows estimation of the optimal size of the Laval nozzle for the given conditions, its shape, and obtain a flow profile depending on its initial characteristics defined in the previous section of the nozzle. The results of flow simulation can be applied to calculate the flow in circular sections, which are the most common in the current application. The results are confirmed by the solution using the finite element method, and the convergence of the solution in the diffuser is described in the current work. Theoretically, the solution can be applied to a mixture of gases, if peculiarities of physical and chemical transformations and the participation of combustion products are taken into consideration. In this case instead of parameters in the pre-chamber, the parameters of the combustion chamber and the products in it should be used as initial conditions. This calculation will be carried out in future studies of the authors.
Simulation of the thermal state of the blank surface layer at thermal-friction turn-milling
Authors: Sherov K , Tussupova S , Sikhimbayev M , Mussayev M , Ainabekova S , Imanbayev Ye , Karsakova N , Abisheva N
Published: February 2021

As a result of research, it was revealed that there is a problem of turning accurate large-sized, long parts, which is associated with an increase in productivity and quality of processing, as well as with a decrease in the cost of turning operations. To solve this problem, the authors developed a method of thermo-friction turn-milling and tool design. However, the lack of knowledge of the thermal phenomena occurring in the contact layer “blank-tool” during processing inhibits the widespread use of the proposed method. In this regard, this article simulated the thermal state of the surface layer during cutting. The results of modeling the thermal state of the surface layer when processing parts from difficult materials with thermofriction turn-milling are presented. The influence of cutting conditions and geometric parameters of the tool on the distribution of the temperature field of the surface layer of the workpiece during thermo-friction turn-milling is considered.
On the features of Hurst Exponent estimates of the Fractional Brownian motion calculated by the R/S-analysis
Authors: Ponomareva O , Porshnev S , Solomakha E
Published: February 2021

The article presents the analysis results of the dependence of the accuracy in estimating Hurst exponent of the Fractional Brownian motion by the R/S-analysis towards the method parameters Lmin
, Lmax
. It is found that the estimation of the Hurst exponent coinciding with its corresponding value is used to generate Fractional Brownian H〈mod〉 motion only when

L

max

=

L

max

〈
t
r
u
e
〉

. Otherwise, Hurst Exponent Estimate H depending on the value Lmax
varies in the span [0.25; 1.12]. The result obtained points out that it is necessary to critically revise the results of a number of studies where in order to analyze and forecast the dynamics of complex systems of different nature (for example, in economic ones) the authors employed the R/S-evaluation exponents of the Hurst exponent H of the time series (TS), composed of the exponents characterizing the state of the given system at a certain point.
Analysis, synthesis and modelling of air individual smart rescue system
Authors: Rakov D
Published: February 2021

The morphological approach is a successful analytical tool for development schematic, conceptual and preliminary design of new engineering systems in Aerospace. This investigation used a morphological approach to engineering solutions development as well as to tools for creating promising individual smart rescue system on conceptual design stage. The problem was solved in two stages. At a higher level of the hierarchy, the principle of action in morphological box was chosen. In the second phase, specific engineering solutions were explored. Analysis of engineering systems, solutions and solving technique and systems and their potential opportunities with technique provide correct guidelines to supply the reasonable decisions. Flight simulations, depending on different initial conditions, were performed using the LANE program.
Enhancing the efficiency of rebar use in reinforced concrete products’ manufacturing
Authors: Sherov K , Serova R , Yessirkepova A , Mussayev M , Zhanakov K , Smailova B , Turusbekova A , Mazhitova L
Published: February 2021

The article analyzes the state of rebar use in the conditions of construction enterprises of the Republic of Kazakhstan (RK). As a result of the research, it was found that today the domestic industry of construction materials is able to satisfy just a part of the needs of the Republic of Kazakhstan’s construction complex, and as a result, a significant share of the market is occupied by imported products, preventing a shortage of virtually all types of construction materials. The current situation has a negative impact on the prime cost of construction products’ manufacturing. It was also established that there is a high consumption of rebar for wastes, which exceeds the standards defined by State Standard and is about 2%. The consumption of rebar in this ratio also leads to an increase in the prime cost of reinforced concrete products’ manufacturing. For the effective use of reinforcing bars, which are the main components in reinforced concrete products’ manufacturing, it is proposed to separately use wastes of reinforcing bars, rods and wires to manufacture certain types of reinforced concrete products.
Reliability indexes of vibrating platforms for compaction of construction mixtures
Authors: Rogovskii I L , Delembovskyi M M , Voinash S A , Scherbakov A P , Teterina I A , Sokolova V A
Published: February 2021

In the article of experimental research and a particularly important prerequisite is to establish the required values with the least error, because the reliability of the information obtained from the processing of experiments is key to determine the true value of a parameter. According to the results of the study, data were obtained on the actual operating time for failure of the elements of the vibrating platforms VB-10V. The research identified the main prefabricated units and parts that failed: motor, gearbox, synchronizer, vibrator, propeller shafts, clutches. At the same time, cardan shafts and couplings failed the most. In some cases, the destruction of bearings in vibrating exciters has been demonstrated. The method of determining the number of experiments and estimating the error in measuring the studied parameters is based on the basic provisions of probability theory and mathematical statistics. The results of the research indicate a low level of reliability of the cardan shaft, which leads to a long downtime at an unscheduled time of repair, which is 0.8-1.2 hours in the presence of spare parts in stock. As a result of processing the statistical information of the cardan shaft reliability indicators, it was found that the average resource is 261.95 hours, the standard deviation is 53.2 hours, the coefficient of variation is 0.27.
The use of the system dynamics model to determine the probability of company default
Authors: Kurennoy D S , Golembiovsky D Yu
Published: February 2021

This research demonstrates the approach of using the system dynamics model to assess the probability of company default that is a relevant problem in credit risk analysis. System dynamics offers models in which the reality is simulated structurally. According to the principles of system dynamics, the company is represented in the form of continuously interacting elements and external factors. Enterprise dynamics and the enterprise’s resistance to various macroeconomic environments are determined by functional dependencies and differential equations that describe the links between the elements of the model. The behavior of random macroeconomic variables is described with a multivariate ARIMA-GARCH model, which is used in econometrics to predict non-stationary time series. The probability of company default is determined as a result of experiments with the obtained system dynamics model using the Monte Carlo simulation. The estimation of a default probability is the overall share of macroeconomic scenarios leading to the ruin of the enterprise. A comparative analysis of the obtained results and data from Moody’s and Fitch demonstrates the closeness of the probability of company defaults obtained by simulation and corresponding estimates of rating agencies, which makes it possible to conclude that the considered approach is acceptable for estimating the probability of default of a borrower.
Electrical component base testing in process of spacecraft configuration
Authors: Mikhnev D L , Erygin Y V , Rozhnov I P
Published: February 2021

In current conditions and according to the quality level of Electronic Component Base of domestic production and due to the purchase of significant amount of electronic component base of foreign production - additional screening testing, diagnostic non-destructive testing with selective destructive analysis in professional testing centers are necessary. Costs of their performance are insignificant compared to possible losses of material (and not just material) while using spacecraft with bad quality of electrical component base. The authors show the need for additional testing of electronic component base applied in on-board equipment of spacecraft.
Building the strategy for innovative development of industrial enterprises based on network planning methods
Authors: Stupina A A , Antamoshkina O I , Ruiga I R , Korpacheva L N , Kovzunova E S
Published: February 2021

The article substantiates the need to adjust corporate development strategies, business models and production methods, caused by the influence of the fourth industrial revolution (Industry 4.0). Cluster and network structures are capable of ensuring timely digital business transformation. For effective integration into network interaction, it is necessary to form corporate strategies for innovative development based on an effective combination of strategic and operational planning using network methods. The article provides a comparative analysis of the critical path method, the method of evaluation and analysis of programs and projects, the method of graphical assessment and analysis, and the cyclical alternative network model. As a result of the study of network planning methods, it was revealed that the GERT-network modelling allows taking into account the risk factors and uncertainties, and the cyclical alternative network model allows to manage the level of risk and uncertainty. The two-level model of planning and management of industrial production proposed in the article, as well as the developed algorithm for solving the problem of interdepartmental production planning, can be used as the basis for the formation of a strategy for the innovative development of industrial enterprises.
Cyber-control of groups of technological aggregates
Authors: Shukalov A V , Zharinov I O , Zharinov O O
Published: February 2021

Groups of technological aggregates creates a production cyber-segment being controlled autonomously. Electrical automatics aggregate elements are described as some control theory terms with kinematics and dynamics tasks laws being completed. Cyber-control system of groups of machines in production is built as a multi closed-loop scheme with typical two or three loops tracking channels. There is a multi-loop production cyber-control scheme given. The cyber-control specifics include the additional virtual and traditional physical tracking system. The aggregate virtual tracking system control signals are registered in parametric settings of physical tracking system regulators. The aggregate situation cyber-control is done with a digital production avatar.
Troubleshooting technological aggregates based on machine learning
Authors: Kosarevskaia S A , Shukalov A V , Zharinov I O , Zharinov O O
Published: February 2021

The technological aggregates preventive maintenance problem being researched is resistive against a type of failures. The preventive maintenance is a cyber-production control system function and is done by activation of re-arrangement manipulation system, which is used to eliminate technological aggregates failures. The technological aggregates restoration operation technology is viewed as a man substitution in the Industry 4.0 paradigm. The equipment failure is viewed as an incident of cyber-production functional safety system, which is capable to cause a potential complex damage. The equipment robotized maintenance model is oriented to increase the cyber-production functional reliability and to use the machine learning methods to make intellectual the industrial automatics. They analyze the repair and restoration works mechanisms in the process factory level (the physical workshop) and in the analytical factory level (the virtual cloud) for a cyber-production, which interact with operation system. There is the equipment robotized maintenance algorithm proposed, which gives the data to the control system for its actual state. There is the automatic control system scheme proposed to make a technological aggregates preventive maintenance. An option how to change a failed unit is selected after the technological aggregates conditions pre-history analyzing obtained in the stage of machine learning of collected statistics.
Modification of carbon fiber by magnetite particles
Authors: Kornilitsina E V , Lebedeva E A , Astaf’eva S A , Trukhinov D K
Published: February 2021

In order to expand the application range of carbon reinforced composite materials in shielding field, this paper aimed to modify the chopped carbon fiber (CF) by magnetite particles with ultrasonic treatment. The modification was carried out in three stages and the increasing amount of the cover was proved by TGA analyze. SEM analyze is showed the most part of CF surface was coated by magnetite particles Fe3O4. Also it was noticed some agglomeration on each stages what is possibly connected with high surface energy of these particles. The chemical compound of the coating corresponds to ferrous oxide (II and III) what is confirmed by Raman spectroscopy.
Elastic compounds based on epoxy terminal oligomers synthesized on the basis of an oligoester
Authors: Slobodinyuk A I , Senichev V Yu , Pogorel’tsev E V
Published: February 2021

The physico-mechanical and structural characteristics of a series of elastomers based on epoxy terminal oligomers synthesized using a crystallizing oligoester were investigated. It was found that the use of isophorone diisocyanate allowed obtaining polymeric materials with a noticeable advantage both for the physical and mechanical characteristics, and for the temperature diapason of application as well. It was shown that the mentioned advantage of isophorone diisocyanate could be explained by the higher degree of microphase separation between soft and hard blocks in the polymeric matrix constructed using this component. New materials can be used as a base for compounds for various purposes.
Development of gradient polymer composite and technology for its production for revolved parts with increased surface wear resistance
Authors: Sharshin V N , Sukhorukov D V , Sukhorukova E V
Published: February 2021

The work is aimed at creating polymer composite materials with desired properties. One of the ways to create such materials is to create gradient layers characterized by a smooth spatial change (gradient) of properties in the direction of one or two coordinate axes. The results of studies on the rotation of the polymer composition at the time of polymerization are shown. A device for producing polymer composite materials with a gradient layer has been created. The values of the distribution of additives and hardness along the height of the samples are given. Mathematical processing of the experimental results was carried out.
An ordered ranking multi-attributive model for decision-making systems with attributes of control systems software
Authors: Efremova S V , Kartsan I N , Zhukov A O
Published: February 2021

The authors present a compensation model for the general ranking of alternatives in their order of preference, considering the dependence of the attributes of software for spacecraft control systems. Among the discussed features is one that consists in the use of a set of target functions, which cannot be optimized simultaneously, due to their inherent incommensurability and target conflict.