bluuebunny/crossref_metadata_2025 huggingface dataset:
AN INDENTATION METHOD FOR ADHESIVE STRENGTH EVALUATION OF POLYMER COATINGS
Authors:   Gorkunov Institute of Engineering Science UrB RAS, SMIRNOV S.V. , MYASNIKOVA M.V. , PESTOV A.V. , KONOVALOV D.A. , SMIRNOVA E.O. ,   Postovsky Institute of Organic Synthesis UrB RAS
Published: May 2024

An indentation method was developed for adhesive strength evaluation of a polymer coating using the example of an epoxy composition with titanium alkoxide deposited on the surface of low-carbon steel. The method is based on the numerical implementation of the fracture mechanics approach in experimental data processing. It was found that the penetration of a Rockwell indenter perpendicular to the coating surface causes annular delamination buckling of the coating around the indentation, which is due to adhesive bond breaking as a result of radial shear when the coating material is forced out from under the indenter. A controlled parameter in finite element modeling was the experimentally determined width of the coating delamination zone at a fixed indentation depth at which delamination occurred. The adhesive contact conditions were set using the bilinear law of the cohesive zone model, which describes the relationship between the adhesive shear stress and adhesive bond stretching during shear of interacting surfaces in the contact plane. The limiting specific surface energy of adhesive failure was used as a quantitative evaluation criterion for adhesive strength. The optimal value of the limiting specific surface energy of adhesive coating failure was determined for the cohesive zone model parameters that provide the best convergence of the numerical and experimental data.
A COMPREHENSIVE STUDY OF FATIGUE CRACK INITIATION AND GROWTH UNDER VERY HIGH CYCLE TORSIONAL FATIGUE LOADING
Authors:   Institute of Computer Aided Design RAS, NIKITIN I.S. , NIKITIN A.D. , STRATULA B.A.
Published: May 2024

This paper investigates the fatigue behavior of smooth specimens made of VT3-1 titanium alloy under fully reversed loading conditions. Mathematical modeling results are presented for the fatigue fracture of smooth specimens under high cycle torsional fatigue loading. The fatigue quasi-crack initiation and growth are calculated using a multimode two-parameter model of fatigue damage accumulation. The surface and subsurface quasi-crack initiation under torsional loading is studied. The numerical results are in good agreement with experimental data and can be used to predict the change in crack growth mechanisms under complex multiaxial loadings such as torsion.
INFLUENCE OF MINOR ALUMINUM ADDITION ON THE SUPERPLASTIC DEFORMATION OF A MICRODUPLEX CU-ZN ALLOY
Authors:   MISIS University of Science and Technology, YAKOVTSEVA O.A. , KABOYI P.K. , IRZHAK A.V. , MIKHAILOVSKAYA A.V. ,   Institute of Microelectronics Technology and High-Purity Materials RAS
Published: May 2024

High residual porosity in superplastically deformed brass carries the risk of reducing the mechanical properties. Multicomponent brasses demonstrate lower residual porosity, associated with a lower grain size and more effective accommodation mechanisms of grain boundary sliding. In this paper, a comparison is made of microstructural evolution in the prepolished surface and in the bulk of duplex brass samples and brass samples with minor aluminum addition during steady-state superplastic deformation. After superplastic deformation, dislocation clusters and dislocation walls are revealed in the α-grains of both alloys, indicating the activation of the dislocation creep mechanism. It is shown that aluminum reduces the contribution of grain boundary sliding along the phase boundaries from ~75 to ~30% and causes strain localization in the ß-phase region with the formation of less than ~300-nm grains as a result of dynamic recrystallization. Alloying with 0.4% Al reduces the flow stress by 20%, increases the relative elongation by a factor of 1.5, and decreases the amount of residual porosity by a factor of 3. This leads to a much lower loss of strength in superplastically deformed specimens at room temperature.
REFINED ENGINEERING THEORY OF FRACTURE WITH A TWO-PARAMETER STRENGTH CRITERION
Authors:   Lavrentyev Institute of Hydrodynamics SB RAS, KLYUCHANTSEV V.S. , KURGUZOV V.D. , SHUTOV A.V.
Published: May 2024

We present a refined engineering theory of cracks, based on a two-parameter strength criterion. Unlike the basic theory, the refined approach utilizes an improved algorithm for the regular stress component computation. This improvement allows extending the applicability range of the engineering theory to longer cracks. The two-parameter Leonov-Panasyuk-Dagdale fracture criterion serves as a basis. A coupled fracture criterion includes a strain-based criterion, which is formulated at the tip of the true crack, as well as a stress-based criterion, formulated at the tip of a fictitious crack. Based on the refined criterion, quasi-brittle fracture curves are constructed for a compact specimen, a strip with an edge crack, and a beam under four-point bending. To validate the new refined fracture criterion, we present simulation results of quasi-brittle fracture for structures made from various virtual materials. The corresponding virtual materials are modeled using a nonlocal damage accumulation theory accounting for the average size of the aggregate state of the material. Additionally, various classes of damage accumulation hypotheses are considered. Analysis of various types of virtual materials provides insights into the impact of hypotheses behind the engineering theory. For each type of material, the influence of the microstructural length scale on the overall structural strength is investigated. The analysis shows that the refined engineering theory has a wider range of applicability as compared to the basic theory based on two-parameter strength criteria.
INVESTIGATION OF DYNAMIC CHARACTERISTICS OF IMPERFECT FG BEAMS ON THE WINKLER-PASTERNAK FOUNDATION UNDER THERMAL LOADING
Authors:   University of Ain Temouchent, ABDELBARI S. , ATTIA A. , BOURADA F. , BOUSAHLA A.A. , TOUNSI A. , GHAZWAN M.H. ,   Jazan University
Published: May 2024

The interest of the present paper is the analysis of free vibration of imperfect functionally graded (FG) beams resting on foundations (with two elastic parameters). The FG beam is made of temperature-dependent metal (Al)/ceramic (Al2O3) material, which is graded in the thickness direction and subjected to various thermal loads (uniform and nonuniform). The appearance of microvoids is considered as porosity in the body structure. Two models of the symmetric porosity distribution are examined. The studied one-dimensional (1D) structure is modeled by employing simple three-variable higher-order integral formulations. Zero traction on the free surface of the 1D structure is gained by using the sinusoidal warping function in the current model, which avoids correction factors. Analytical modeling of structures is carried out using the Hamilton principle and Navier approach to derive the equations of motion and the analytical solution of the current model. Several examples of the free vibration analysis are presented in graphical and tabular forms. A detailed parametric analysis is performed to illustrate the impact of several beam parameters, such as dimensions, inhomogeneity and porosity indices, as well as of the foundation reaction on the fundamental frequency of imperfect FG beams.
STRUCTURE, MECHANICAL AND TRIBOLOGICAL PROPERTIES OF TI-CR-C-NI-FE COMPOSITE COATINGS
Authors:   Merzhanov Institute of Structural Macrokinetics and Materials Science RAS, ANTIPOV M.S. , BAZHIN P.M. , KONSTANTINOV A.S. , CHIZHIKOV A.P. , ZHIDOVICH A.O. , STOLIN A.M.
Published: May 2024

Here we discuss the use of composite cermet SHS electrodes from materials based on titanium carbide, chromium carbide, and nichrome obtained by SHS extrusion for the electrospark deposition of Ti-Cr-C-Ni-Fe composite coatings on metal substrates made of high-speed steel R6M5. Four electrospark alloying modes are considered which correspond to electric discharge energies of 0.2, 0.3, 0.6, and 1.0 J. The plotted experimental curves of the total anode erosion and the total cathode weight gain on the alloying time have a classical form. The effect of the electrospark alloying modes on the structure, mechanical (hardness) and tribological properties of the obtained composite coatings is studied. It is shown that the coating consists mainly of a matrix based on two Cr-Ni-Fe-Csolid and Fe0.7Ni0.3 phases and reinforcement complex carbide Ti0.8Cr0.2C particles, the size of which decreases to less than 100 nm with proximity to the substrate. The hardness of the resulting composite coatings is 10.6-13.5 GPa. The major fraction of carbide particles in the SHS electrode melts during electrospark alloying, and with increasing discharge energy the number of transferred grains in the solid phase increases by a factor of up to 9. Depending on the discharge energy of electrospark alloying, we determine the transfer coefficients of the SHS electrode, the run-in areas of the resulting coatings, and the amount of wear of the coating and counterbody.
EFFECT OF TANTALUM ON THE IMPACT RESISTANCE OF 12% CR STEELS SUBJECTED TO THERMOMECHANICAL TREATMENT
Authors:   Belgorod State University, FEDOSEEVA A. , DOLZHENKO A.
Published: May 2024

The effect of tantalum on the impact resistance of 12% Cr steels with different tantalum content (12CrTaNb and 12CrNb) was investigated in impact tests in the temperature range from -40 to +120°C with determining the brittle-ductile transition temperature as the temperature in the middle between the upper and lower shelf energies. Both 12% Cr steels were thermomechanically treated by alternating 1050°C annealing and forging in addition to standard normalizing treatment with high-temperature tempering. It was found that for Ta-alloyed 12% Cr steel, the entire fracture toughness versus temperature curve is 30-50 J/cm2 higher over the entire temperature range, including the upper and lower shelf energies, and the brittle-ductile transition temperature is 10°С lower. The main structural parameters of Ta-alloyed 12% Cr steel which can have a beneficial effect on toughness are a smaller initial austenite grain size, a larger average size but lower density of M23C6 carbide particles along low-angle martensite lath boundaries, and a larger volume fraction of VX carbonitrides.
A STUDY OF THE STRUCTURE AND MECHANICAL PROPERTIES OF NB-MO-CO-X (X = HF, ZR, TI) REFRACTORY HIGH-ENTROPY ALLOYS
Authors:   Belgorod State University, PANINA E.S. , YURCHENKO N.YU. , TOZHIBAEV A.A. , MISHUNIN M.V. , ZHEREBTSOV S.V. , STEPANOV N.D.
Published: May 2024

Refractory high-entropy alloys (HEAs) are a new class of metallic materials based on group 4-6 elements of the periodic table with possible additions of Al, Si, Re, C, or B. Some single-phase refractory HEAs can maintain high strength up to 1600°C, while multiphase compositions have more attractive specific properties at temperatures up to 1200°C. Here we examine the structure and mechanical properties of refractory HEAs Nb30Mo30Co20Hf20, Nb30Mo30Co20Zr20, and Nb30Mo30Co20Ti20 (at %). The alloys consisted of an intermetallic B2 matrix and particles of a disordered bcc phase, as well as a minor volume fraction of additional bcc (Nb30Mo30Co20Hf20 and Nb30Mo30Co20Zr20) or fcc (Nb30Mo30Co20Ti20) phases. When tested for uniaxial compression, Nb30Mo30Co20Ti20 alloy showed higher yield strength in the temperature range of 22-1000°C than Nb30Mo30Co20Hf20 and Nb30Mo30Co20Zr20 alloys. Nb30Mo30Co20Zr20 alloy did not fail at temperatures of 22-800°C to a given 50% strain, while Nb30Mo30Co20Ti20 alloy turned out to be brittle. All alloys demonstrated high strain hardening in the temperature range of 22-800°C, and they can compete in terms of specific strength with commercial nickel and cobalt superalloys.
MESO-MACRO ENERGY EXCHANGE IN SHOCK-WAVE PROCESSES AND DYNAMIC STRENGTH OF AB2 STEEL
Authors:   Institute for Problems in Mechanical Engineering RAS, MESHCHERYAKOV YU.I.
Published: May 2024

Impact tests of low-alloy martensitic-bainitic steel AB2 showed that the scale of dynamic deformation and the fracture mechanism change in a threshold manner. The change in the mechanism and scale of fracture is triggered by the resonant excitation of large-scale structural elements of the material (grain conglomerates) due to plastic flow oscillations. In this case, the grain-boundary mechanism of dynamic fracture is replaced by a transcrystalline one. Beyond the strain rate threshold, mesoscopic elementary carriers of dynamic deformation are divided into two groups: low-velocity and high-velocity. Accordingly, the velocity distribution of mesoparticles shows two humps. The velocity spread of mesoparticles sharply increases under these conditions, while the mass velocity defect (change in the shock wave amplitude) becomes negative. The latter fact indicates the local acceleration of mesoparticles in discrete regions of the target (the so-called shooting of mesoparticles in the shock wave direction). Transcrystalline cracks are randomly distributed throughout the sample and have a random orientation.
STRUCTURE FORMATION IN SURFACE LAYERS OF ALUMINUM AND TITANIUM ALLOYS DURING PLASMA CUTTING
Authors:   Institute of Strength Physics and Materials Science SB RAS, CHUMAEVSKII A.V. , NIKOLAEVA A.V. , GRINENKO A.V. , PANFILOV A.O. , KNYAZHEV E.O. , CHEREMNOV A.M. , UTYAGANOVA V.R. , BELOBORODOV V.A. , SOKOLOV P.S. , GURIANOV D.A. , KOLUBAEV E.A. ,   ITS-Siberia LLC
Published: May 2024

This paper explores the structure and changes in the mechanical properties, chemical composition and surface morphology of aluminum alloys AA5056, AA2024 and Grade2 titanium alloy after high energy impact during plasma cutting. The studies show that plasma cutting causes the formation of a subsurface layer with a dendritic structure typical of cast material and with a partially altered chemical composition. The subsurface layer material is significantly softened when cutting thermally hardened alloy AA2024, but changes slightly when cutting AA5056 alloy. During plasma cutting of Grade2 titanium alloy in protective atmosphere, the presence of even a small amount of atmospheric oxygen leads to the formation of oxides in the layer closest to the surface, which have microhardness values more than 5-7 times higher than the base metal hardness. Below the surface layer with a molten structure, a heat affected zone is formed where the structure of the base metal is changed as a result of thermal influence. Significant changes in this area are characteristic only for thermally hardened alloy AA2024. Metal flow in the cutting zone initiated by the plasma jet and shielding gas flow occurs in both laminar and vortex modes. Inhomogeneous metal flow in the cutting zone and nonoptimal process parameters lead to the formation of structural heterogeneities and defects of different structural and scale levels on the surface of the samples.
LOCALIZED PLASTICITY PATTERN AT THE PREFRACTURE STAGE: ORIGIN AND DEVELOPMENT
Authors:   Institute of Strength Physics and Materials Science SB RAS, ZUEV L.B. , KHON YU.A.
Published: May 2024

A pattern of macroscopic deformation bands with a characteristic size of ~10 mm was revealed experimentally in a uniaxially deformed sample at the prefracture stage prior to macroscopic necking. The bands moved at different velocities to the place of subsequent necking. The observed banding pattern in the deformed medium was described using two identified dynamic order parameters, which are the amplitudes of unstable plastic and elastic deformation modes. The change in the dynamic order parameters was described by a system of two coupled nonlinear parabolic equations. Analysis of solutions to the equations revealed the conditions for the formation and development of the found pattern at the prefracture stage.
MECHANICAL PROPERTIES OF SINTERED AL-SN-FE ALLOYS
Authors:   Institute of Strength Physics and Materials Science SB RAS, RUSIN N.M. , SKORENTSEV A.L. , AKIMOV K.O.
Published: May 2024

Plastic flow under compression was studied in samples of Al-Sn-Fe alloys produced by sintering from elemental powder mixtures. Some of the sintered composites were additionally compacted at 250°C in a closed mold at a pressure of 300 MPa, and some were processed via equal-channel angular pressing using route A (ECAP-A) at the same temperature. A key structural feature of the sintered alloys is the presence of agglomerates of solid Al3Fe particles cemented with tin, formed in place of iron powder particles as a result of interaction between Al and Fe during sintering. The agglomerates have high strength but are sufficiently ductile owing to tin. They do not break during deformation and effectively suppress the propagation of localized flow bands and microcracks. In compression tests of three-phase Al-20Sn-17Al3Fe composite samples, the particle agglomerates retained their shape and moved as solid structures, while the samples showed good ductility during testing. In ECAP processing via route A, the agglomerates were pulled in the direction of material flow, which negatively affected their ductility in subsequent compression tests.
STRUCTURE AND VIBRATIONS OF FREE NIN CLUSTERS (N < 20)
Authors:   Institute of Strength Physics and Materials Science SB RAS, BORISOVA S.D. , RUSINA G.G.
Published: May 2024

The binding energy, equilibrium geometry, and vibration frequencies of small free Nin clusters (n < 20) were calculated using interatomic interaction potentials calculated in an embedded atom method. Calculations of the energy parameter of stability АЕ2 and dissociation energy showed that the most energetically stable clusters are those with the magic numbers of atoms n = 4, 6, 13, 19. Calculations of atomic vibrations revealed that the dynamic contribution to the stability of clusters is determined by the minimum vibration frequency, whose extreme values fall on clusters with the magic numbers of atoms n = 4, 6, 13, 19. The maximum vibration frequency varies nonmonotonically and for clusters with n < 19 it has no clear extreme values. This result is consistent with available experimental data on stable structures of small and medium-sized metal clusters.
THE USE OF HARD AND SOFT BALL MODELS FOR LATTICE DISTORTION EVALUATION IN B2 HIGH-ENTROPY SHAPE MEMORY ALLOYS
Authors:   Saint Petersburg State University, RESNINA N.N. , BELYAEV S.P. , ANDREEV V.A. , PONIKAROVA I.V. ,   Baikov Institute of Metallurgy and Materials Science RAS
Published: May 2024

The applicability of two most common approaches to distortion evaluation in high-entropy shape memory alloys with B2 structure was discussed. The distortion was calculated for a two-component TiNi alloy and six-component Ti-Hf-Zr-Ni-Cu-Co alloys of different chemical composition using the hard and soft ball models. Both models were shown to be inapplicable for calculating lattice distortion because they predict a high distortion value even for two-component Ti49Ni51 alloy. The very high distortion values obtained for all alloys indicate that the alloys would have to form only an amorphous structure. However, this is inconsistent with experimental studies, showing that all the studied alloys crystallize from the melt with the formation of the B2 phase. A modification of the considered models is proposed, taking into account that the TiNi alloy is a chemical compound (intermetallic compound) formed with a change in the spatial distribution of electron density around the nuclei of interacting atoms and, as a consequence, a change in the atomic sizes. The proposed approach gives the distortion values that are consistent with the previously established criteria for crystal structure stability for alloys with a less than 5% content of additional components.
TEMPERATURE DEPENDENCE OF THE DEFORMATION BEHAVIOR OF HIGH-ENTROPY ALLOYS CO20CR20FE20MN20NI20, CO19CR20FE20MN20NI20С1 AND CO17CR20FE20MN20NI20С3. MECHANICAL PROPERTIES AND TEMPERATURE DEPENDENCE OF YIELD STRENGTH
Authors:   Institute of Strength Physics and Materials Science SB RAS, ASTAFUROVA E.G. , REUNOVA K.A. , ASTAFUROV S.V. , ASTAPOV D.O.
Published: May 2024

This paper discusses the temperature dependence of the mechanical properties of multicomponent alloys Co20Cr20Fe20Mn20Ni20 (Cantor alloy), Co19Cr20Fe20Mn20Ni20С1 and Co17Cr20Fe20Mn20Ni20С3 under uniaxial static tension in the temperature range from 77 to 473 K. It is shown that after thermomechanical treatment all the alloys have an fcc crystal structure, but unlike single-phase Co20Cr20Fe20Mn20Ni20 and Co19Cr20Fe20Mn20Ni20С1 alloys, the alloy with 3 at % carbon exhibits large incoherent chromium carbides. Alloying with carbon causes solid solution strengthening of the austenitic phase and dispersion hardening, and promotes grain refinement in the Cantor alloy. Solid solution strengthening contributes to an increase in the athermal and thermal stress components of σ0.2, leading to higher yield stress values and stronger temperature dependences σ0.2( T ) in Co19Cr20Fe20Mn20Ni20С1 and Co17Cr20Fe20Mn20Ni20С3 alloys than in the Cantor alloy. The results of X-ray diffraction and microscopic analysis indicate that despite the differences in the total concentration of interstitial atoms in Co19Cr20Fe20Mn20Ni20С1 and Co17Cr20Fe20Mn20Ni20С3 alloys, the concentrations of carbon dissolved in the crystal lattice of the austenite phase are close. However, the higher strength properties of Co17Cr20Fe20Mn20Ni20С3 compared to Co19Cr20Fe20Mn20Ni20С1 are determined primarily by grain boundary strengthening and, to a lesser extent, by dispersion hardening. Both factors such as lowering the deformation temperature and alloying with carbon contribute to an increase in the deforming stresses of the Cantor alloy. It is shown that alloying with carbon affects the staged plastic flow of the Cantor alloy: the tensile curves of Co19Cr20Fe20Mn20Ni20С1 carbon alloy exhibit a well-defined stage of microplastic deformation, and the flow curves of Co17Cr20Fe20Mn20Ni20С3 alloy at the initial stages of plastic flow have a parabolic shape, typical of the deformation of alloys with large incoherent particles. The elongation to failure of Co20Cr20Fe20Mn20Ni20 and Co19Cr20Fe20Mn20Ni20С1 alloys increases linearly with decreasing deformation temperature, i.e., the mechanical properties of single-phase alloys are improved in the region of low test temperatures. For Co17Cr20Fe20Mn20Ni20С3 alloy, an increase in strength properties during low-temperature deformation is accompanied by a decrease in ductile characteristics, and the alloy becomes brittle from the viewpoint of macromechanical behavior.
EFFECT OF HEAT TREATMENT ON THE STRUCTURE AND PROPERTIES OF TITANIUM ALUMINIDE ALLOY TI-AL-V-NB-CR-GD PRODUCED BY SELECTIVE ELECTRON BEAM MELTING
Authors:   All-Russian Scientific Research Institute of Aviation Materials - NRC “Kurchatov Institute”, PANIN P.V. , LUKINA E.A. , NAPRIENKO S.A. , ALEKSEEV E.B.
Published: May 2024

This study examines the influence of hot isostatic pressing and heat treatment on the microstructure and mechanical properties of samples manufactured by selective electron beam melting (SEBM) of metal powder composition (MPC fraction 40-100 pm) of a new six-component intermetallic beta-solidifying TiAl alloy Ti-44.5Al-2V-1Nb-2Cr-0.1Gd, at % (Ti-31.0Al-2.5V-2.5Nb-2.5Cr-0.4Gd, wt %). It is shown that SEBM with a high line energy input (El = 285 J/m) produces a fine-grained microstructure in the as-built material with a grain size of 5-14 pm and residual porosity of less than 0.5 vol %. An increase in the electron beam current (I) from 9.5 to 19.0 mA causes Al evaporation, and as a result the fraction of large columnar grains (d = 30-100 pm in width, h = 150-400 pm in height) formed mainly in Al-depleted regions (layers) increases. Heat treatment of the as-built SEBM samples by two-stage annealing in the (a + y) and (a2 + у + в) phase fields or by thermal cycling in the (a + y) phase field leads to complete or partial fragmentation of columnar grains. For the samples produced at lower values of I, a combined post-processing treatment by hot isostatic pressing in the а phase field and two-stage annealing completely eliminates residual porosity and transforms the columnar structure into a fine-grained one with a grain size of less than 150 pm. As a result, the achieved short-term mechanical characteristics at 20 °С (аВ = 525 ± 5 MPa, 5 = 1.1%) and 750 °С (аВ = 405 ± 10 MPa, 5 = 3.8%) are comparable to those of the studied TiAl alloy in the as-cast state.
EFFECT OF SILVER ADDITION TO HIGH-ENTROPY ALLOYS AL0.5COCRCU0.5FENI AND AL0.5COCRCUFENI ON THEIR MICROSTRUCTURE, PHASE COMPOSITION, MICROHARDNESS AND SURFACE OXIDE LAYER FORMATION
Authors:   South-Ural State University, SAMOILOVA O.V. , PRATSKOVA S.E. , SUDARIKOV M.V. , SHABUROVA N.A. , SULEIMANOVA I.I. , TROFIMOV E.A.
Published: May 2024

High-entropy alloys (HEAs) consisting of five or more components in an equimolar ratio are attracting increasing attention due to a unique combination of various properties. Alloying HEAs with small amounts of certain elements (most often rare earth, trace or noble metals) is a promising way to improve the characteristics of such alloys and control their properties. This paper reports the results on the microstructure, phase composition, and microhardness of cast AgxAl0.5CoCrCuyFeNi HEAs (x = 0, 0.1; y = 0.5, 1.0). The effect of silver addition on the oxidation behavior of the studied HEAs at 700°C was determined. The morphology, phase and chemical composition of the resulting oxide film were studied. It was shown that the introduction of silver improves the mechanical characteristics of the alloys, but deteriorates the oxidation resistance due to the formation of copper-silver eutectic in the alloy microstructure, leading to a change in the morphology and phase composition of the formed oxide layer. Along with the solid solution of (Al, Cr)2O3 oxides and CuCr2O4, NiCr2O4 spinels, the addition of silver leads to the formation of copper oxide CuO and a small amount of silver oxide Ag2O in the surface film.
EXPERIMENTAL AND THEORETICAL STUDY OF SPACE DEBRIS IMPACTS ON SHIELDED TARGETS
Authors:   Institute of Strength Physics and Materials Science SB RAS, BATUEV S.P. , BURKIN V.V. , DYACHKOVSKY A.S. , ISHCHENKO A.N. , RADCHENKO P.A. , RADCHENKO A.V. , SAMMEL A.YU. , STEPANOV E.YU. , CHUPASHEV A.V. ,   Institute of Applied Mathematics and Mechanics, National Research Tomsk State University
Published: May 2024

A comprehensive study is reported on highand hypervelocity impacts of a steel ball simulating a space debris particle on shielded targets. Experimental studies of high-velocity impact of a steel ball were performed in the velocity range up to 2500 m/s. The obtained data were used to verify the mathematical model and numerical algorithm. Numerical modeling of space debris impact on a shielded target was carried out in the impact velocity range of 1400-7000 m/s using the finite element method implemented in the original EFES software package. The proposed failure algorithm can describe the fragmentation of the material and the formation of new contact boundaries without computational mesh distortion. The specific features of shock wave processes and the destruction of the target and impactor at different impact velocities were investigated.
Avodah: Perspektif Alkitab tentang pekerjaan dan pelayanan
Authors: Pandey Dylfard Edward
Published: May 2024

AbstractFrom a church perspective, work and ministry are often considered two different and contradictory things that cannot be combined. The difference in seeing work and ministry as secular and sacred gives rise to many crises, debates and controversies in church life. Therefore, to address this, research efforts were made on these two things in the context of the term avodah as seen from a Biblical perspective and as the focus of research. In carrying out this research, qualitative methods were used with a literature study approach and inductive analysis to collect, analyze and validate data. Hebrew Terminology avodah is a comprehensive perspective with a unified, compound meaning, namely work, service and worship; and at the same time multi-application where these three meanings are applied. Avodah is a perspective where service and work are worship and a form of worship that is continuously carried out in the lives of believers. Avodah with the meaning of work, service and worship was deliberately designed by God to cover aspects of the spirit, soul and body in human life. The idea of Avodah also shows that service and work as a form of worship and worship are tools that can transform the lives of believers to become like and in the image of God.Key words: Avodah, Work, Worship, Ministry, Be-VocationalAbstrakDalam perspektif gereja pekerjaan dan pelayanan seringkali dianggap dua hal yang berbeda dan bertolak belakang sehingga tidak dapat disatukan. Perbedaan dalam melihat pekerjaan dan pelayanan sebagai yang sekuler dan yang sakral menimbulkan banyak krisis, perdebatan dan kontroversi dalam kehidupan bergereja. Karena itu, untuk menyikapi hal ini dilakukan upaya penelitian tentang kedua hal ini dalam konteks terminolgi avodah sebagaiman dilihat dalam perspektif Alkitab dan sebagai fokus penelitian. Dalam pelaksanaan penelitian ini digunakan metode kualitatif dengan pendekatan studi pustaka dan analisis induktif guna mengumpulkan, menganalisa dan mengabsahkan data. Terminology Ibrani avodah merupakan sebuah perspektif yang komprehensif dengan memiliki satu kesatuan arti yang majemuk yaitu pekerjaan, pelayanan dan penyembahan; dan sekaligus multi aplikasi dimana ketiga makna tersebut diterapkan. Avodah merupakan perspektif dimana pelayanan dan pekerjaan merupakan sebuah penyembahan dan bentuk ibadah yang terus menerus dilaksanakan dalam kehiduapn orang percaya. Avodah dengan pengertian pekerjaan, pelayanan dan penyembahan sengaja dirancang Allah untuk melingkupi aspek roh, jiwa dan tubuh dalam kehidupan manusia. Gagasan Avodah juga menunjukkan bahwa pelayanan dan pekerjaan sebagai bentuk penyembahan dan ibadah merupakan alat yang sedemikian rupa dapat mentransformasi kehidupan orang percaya untuk menjadi serupa dan segambar dengan Allah.Kata kunci: Avodah, Kerja, Ibadah, Pelayanan, Bivokasi
Quando se percebe que o valor é construído? a cocriação de valor na experiência dos clientes em serviços financeiros
Authors: Oliveira Caroline Lujan de , Morais Fábio Rodégio de
Published: May 2024

Objetivo do estudo: O objetivo deste estudo foi propor a adequação do modelo teórico de cocriação de valor, aplicado aos serviços financeiros.
Metodologia/Abordagem: Com abordagem quantitativa-explicativa e estratégia Survey, os dados foram coletados por meio de questionário (Google Forms) aplicados aos clientes de serviços financeiros e análises estatísticas descritivas e inferenciais (IBM SPSS Amos 24.0.0).
Principais resultados: O modelo teórico de cocriação de valor ajustado para serviços financeiros foi aceito e os índices se enquadraram positivamente nos valores de referência da modelagem de equações estruturais.
Contribuições teóricas/metodológicas: Ampliou-se a análise do processo de cocriação de valor aplicado ao serviço financeiro e verificou-se novas variáveis que contribuem com o processo de cocriação de valor.
Relevância/originalidade: O estudo aponta a existência de fatores considerados essenciais para a percepção de cocriação de valor, dispostas na plataforma interativa de capacidades e recursos que foram propostos como métricas para o dimensionamento do modelo disponível contribuindo para a coleta de dados e testagens empíricas em pesquisas futuras.
Os impactos causados no sistema processual penal brasileiro com a abuso de autoridade cometido pelos representantes do poder judiciário
Authors: Silva Pedro Augusto da , Oliveira Filho Enio Walcácer de
Published: May 2024

O abuso de autoridade cometido por representantes do poder judiciário é uma preocupação crescente no Brasil, suscitando debates sobre seus impactos no sistema processual penal. Este estudo visa analisar esses impactos e suas consequências. O presente trabalho busca investigar como o abuso de autoridade afeta o sistema processual penal brasileiro, examinando suas ramificações e implicações para a justiça e os direitos individuais dos cidadãos. Este trabalho baseia-se em uma revisão bibliográfica, analisando textos acadêmicos, jurisprudência e legislação pertinente para entender as nuances do abuso de autoridade e suas implicações no contexto do sistema processual penal brasileiro. Os resultados destacam que o abuso de autoridade compromete a imparcialidade, a equidade e a eficiência do processo penal, minando a confiança pública na justiça e violando os direitos fundamentais dos acusados. Conclui-se que o abuso de autoridade representa uma séria ameaça ao Estado de Direito e à democracia, exigindo medidas eficazes para prevenir e punir tais condutas, a fim de preservar a integridade e a legitimidade do sistema processual penal brasileiro.
O EJA-TEC em Goiás e o uso do WhatsApp®: um fardo para estudantes e professores
Authors: Barbosa Elisa Pimentel , Castro Mad'Ana Desirée Ribeiro de
Published: May 2024

Lançado em 2019, o programa EJA-TEC visa oferecer uma oportunidade de educação a distância para jovens e adultos que buscam concluir sua educação básica. Apesar de sua promessa, o programa promoveu a precarização do trabalho docente e da aprendizagem dos estudantes. Este artigo, ancorado em pesquisa realizada em mestrado na área de educação, traz a análise de dados oriundos de entrevistas feitas com sete professores de duas escolas-polo de Goiânia, inseridas no contexto do programa EJA-TEC. O objetivo principal é apresentar as principais dificuldades dos estudantes no EJA-TEC, com base nas percepções dos professores que trabalham no Programa. Os resultados destacam que a sua implementação negligenciou aspectos importantes e significativos ao processo de aprendizagem, como entender o acesso ou não dos estudantes à tecnologia e à internet e fornecer uma plataforma de ensino adequada às suas condições de estudantes dessa modalidade educativa. Consequentemente, os educandos enfrentam obstáculos significativos para acessar e utilizar a plataforma Moodle e na compreensão dos conteúdos. Em resposta a essas deficiências, os sujeitos recorreram ao uso do WhatsApp®, um aplicativo de mensagens, como ferramenta principal de comunicação e aprendizagem, criando vários obstáculos ao processo ensino-aprendizagem.
Ansiedade, depressão e autoeficácia geral em estudantes de enfermagem antes e durante a pandemia da COVID-19
Authors: Pinto Isabela de Brito , Pompeo Daniele Alcalá , Eid Letícia Palota , Severian Patrícia Fernandes Garcia , Alves Danilo de Miranda , Pompeo Lucca Alcalá , Martins Marlene Andrade , Ribeiro Rita de Cássia Helú Mendonça
Published: May 2024

Comparar os escores de autoeficácia geral e sintomas de ansiedade e depressão em estudantes de graduação em enfermagem antes e durante a pandemia da covid-19. Estudo transversal, analítico e longitudinal, desenvolvido em uma instituição de ensino superior, com universitários dos cursos de enfermagem. Foram aplicados três instrumentos de coleta: caracterização sociodemográfica, Escala Hospitalar de Ansiedade e Depressão e Escala de Autoeficácia Geral e Percebida. Os sintomas de ansiedade foram semelhantes antes e durante a pandemia, mas a depressão foi superior no período pandêmico (p=0,029). Os níveis de percepção de autoeficácia não sofreram alterações significativas nos períodos avaliados. A pandemia da covid-19 influenciou a saúde mental dos estudantes de enfermagem, com elevação dos índices de depressão. Este estudo fornece dados que podem embasar a criação de políticas educacionais e de saúde que tenham como foco a saúde mental de estudantes universitários, especificamente estudantes de enfermagem.
Ensino de geometria plana por meio de tendências da educação matemática – praticando e aprendendo
Authors: Moreira Fernanda Patrícia Pio , Mota Vania Corrêa , Silva Ricardo José Souza da , Sakuno Irêne Yoko Taguchi
Published: May 2024

O artigo tem como objetivo demonstrar que a utilização dessas tendências da Educação Matemática (resolução de problemas, materiais concretos e jogos), para ensinar conteúdos de Geometria Plana contribui para a aprendizagem dos alunos do terceiro ano do Ensino Médio, para assim trazer mais compreensão sobre o conteúdo a ser assimilado. Esta pesquisa é de cunho qualitativo; o campo de estudo foi uma turma de 22 alunos do município de Ji-Paraná/RO. Foi aplicado o jogo “tabuleiro geométrico”, que consiste em uma trilha contendo 60 cartas, sendo elas 30 com as questões que envolvem conteúdos de Geometria plana e 30 com as respostas e um tabuleiro, composto com 22 casas; sinalizado com saída, 20 casas numeradas de 1 a 20 e a chegada. Conclui-se que demonstrar a aplicação dessas tendências, por meio, do jogo facilitou a construção de conhecimentos de forma, espontânea, intuitiva de conceitos de Geometria Plana.
Dinâmica das áreas de preservação permanente no rio Pericumã, Pinheiro, Maranhão
Authors: Oliveira Amerson Lima , Santiago Denise Rodrigues , Dias Joel Artur Rodrigues , Lopes Yuri Vinicius de Andrade , Nascimento Louize , Machado Adilson Matheus Borges , Feitosa Milena Monteiro , Marinho Yllana Ferreira
Published: May 2024

A pesquisa objetivou diagnosticar as condições de uso e cobertura do solo e as condições das APPs na extensão do Rio Pericumã, município de Pinheiro–MA, visando compreender sua relevância no contexto da conservação dos recursos hídricos e biota aquática. Para a geração dos mapas de uso e cobertura do solo, utilizou-se a plataforma MapBiomas e Google Earth Engine para obtenção das imagens dos anos de 1985, 1995, 2005, 2015 e 2022 (30 m de resolução). Para as análises das APPs foram necessárias às imagens, de 2016 e 2022 (10 m de resolução), processadas no QGIS. Os resultados apontaram a fragmentação nas áreas ao longo do período analisado. Nos anos de 2016 e 2022, os pontos 2 e 4 destacam-se negativamente devido ao avanço das atividades antrópicas, especialmente em áreas urbanas e de pastagem. Conclui-se que esses achados são cruciais para orientar políticas de conservação e gestão ambiental.
Uma questão de linguagem: qual o sentido de "verdade"?
Authors: Cruz Carlos Eduardo Henrique da , Pedrozo Júnior Neurivaldo Campos
Published: May 2024

Os estudos de Linguística Aplicada transcendem a mera aplicação de teorias linguísticas no ensino de idiomas. Ao considerarmos as perspectivas de Moita Lopes (2006, 2009) e Cavalcanti (1986), compreendemos que os debates nesse campo permitem uma interseção entre diversas correntes científicas, como a filosofia e a sociologia, desde que estejam centrados na questão do uso da linguagem. Nesse sentido, esta pesquisa recorre às obras de Foucault (2008, 2019) e Nietzsche (2008) para uma análise filosófica da linguagem, visando entendê-la como um meio de acesso à realidade. Sob essa perspectiva, delineia-se que é por meio da linguagem que nos constituímos como indivíduos e compreendemos o mundo ao nosso redor. Ao considerarmos a linguagem como um processo de construção de significados, percebemos que qualquer prática nesse sentido é influenciada por uma interação circunstancial na qual o sujeito, imerso em relações sociais e de poder, elabora um significado singular para si mesmo. A partir dessa reflexão, compreendemos que não há uma única verdade, mas sim múltiplas verdades, ou melhor, diferentes efeitos de sentido da verdade. Como cada significado é determinado pela conexão feita pelo indivíduo, a verdade não pode ser universal para toda a humanidade, nem mesmo nas ciências; ela é um ponto de observação, um nó em uma vasta rede de significados. Para fundamentar essa reflexão, recorremos aos estudos de Moita Lopes (2006, 2009) e Cavalcanti (1986) para situar essa análise no campo da Linguística Aplicada. Em seguida, utilizamos as contribuições de Vygotsky (1991), Barad (2003) e Buzato (2012) para entender a linguagem como uma prática sócio-interacionista na construção de significados. Por fim, as considerações de Nietzsche (2008) sobre a verdade como uma prática discursiva e a ótica de Foucault (2008, 2019), que argumenta que a verdade é um efeito construído discursivamente, justificam nossa percepção de que a verdade é um fenômeno relativo.
Indices of diet quality among Polish and Spanish physical education students
Authors: Gacek Maria , Kosiba Grażyna , Wojtowicz Agnieszka , López Sánchez Guillermo Felipe , Szalewski Jacek
Published: May 2024

Introduction: A healthy diet is an important factor in implementing health, and the way of eating depends on individual and environmental factors. Objective: The aim of the study was to assess diet quality indices among Polish and Spanish physical education students depending on country of residence and gender. Materials and methods: Research was carried out among 219 students from Poland and 280 from Spain. A questionnaire was used to evaluate views on eating and nutritional habits (Kom-PAN). Based on the daily frequency of consuming specific groups of products, 2 indices were calculated: the pro-healthy diet index (pHDI-10) and non-healthy diet index (nHDI-14). Two-way ANOVA was used for statistical analysis. The level of significance was set at p=0.05. Results: The values of the pro-healthy (pHDI-10) and non-healthy diet (nHDI-14) indices in the group of students were 4.65 and 4.05 (times/day), respectively, which means a low level of both favourable and unfavourable food choices. Students from Poland, regardless of gender, showed a higher level of eating a healthy diet (pHDI-10) than students from Spain. However, the level of the non-healthy diet index (nHDI-14) between students from Poland and Spain differed by gender (p<0.001). In the Polish group, men obtained a higher nHDI-14 index than women (p<0.001), while in Spain, these values were at the same level. Furthermore, it was found that differences between countries occurred only in men, with students from Poland obtaining higher values of the nonhealthy diet index (nHDI-14) than those from Spain (p<0.001), while students from both countries demonstrated similar values. Conclusions: Low levels of healthy and unhealthy diet indices were demonstrated in Polish and Spanish physical education students, with the quality of diet differentiated by country and gender.
CRITERIA ANALYSIS FOR SELECTION OF A FIRE PROTECTION SYSTEM FOR AN OFFICE BUILDING
Authors: Krukowski Marcin , Półka Małgorzata
Published: May 2024

This article describes selecting a fire protection system that would be the most appropriate foran office building. This selection has been executed with the use of the APEKS multi-criteriamethod. The scope of work comprises the design of a hydrant system, which includes a designof a sprinkler system for three above-ground floors and one underground floor, supplied withwater from the municipal mains. Hydraulic calculations are also presented, with a cost estimatebased on catalogues obtained from the various companies. The entire project has been designed inpursuance of regulations and standards applicable in Poland with regard to the relevant buildingand fire protection regulations.
EXPIRED FOAM EXTINGUISHING AGENTS AND EVALUATION OF THEIR SUITABILITY FOR FURTHER USE
Authors: Gniazdowska Justyna , Rabajczyk Anna , Wilczyński Tomasz
Published: May 2024

Foam extinguishing agents are one of the most commonly used and effective means usedduring rescue and firefighting operations. However, their applicability depends on a numberof parameters, which are defined in relevant standards and guidelines. They include substancesthat are characterised by greater or lesser toxicity, such as fluoroorganic compounds, so properhandling of these materials is one of the priorities for their management. The analysis involved3 foam extinguishing agents of different compositions (types FP, AFFF, AR) after the lapse of theirdeclared useful life by the manufacturers. These agents were tested for selected parameters vitalfor proper firefighting operations, i.e. the expansion ratio and condensation times of the agentssubjected to temperature conditioning and the extinguishing efficiency on a small scale.
EXPLORANDO O POTENCIAL DA TECNOLOGIA BRAINNET NA EDUCAÇÃO: COMUNICAÇÃO E APRENDIZAGEM ALÉM DOS LIMITES TRADICIONAIS
Authors: Guimarães Junior José Carlos , Costa Hilke Carlayle de Medeiros , Schmidt Fabrício Leo Alves , Souza Flávio Penteado de , Souza Eryck Dieb , Silva Savio Lima Costa e , Santos Carlos Alberto Feitosa dos , Lindstron Jacqueline Andreucci , Silva Jadilson Marinho da
Published: May 2024

O avanço da tecnologia BrainNet está redefinindo o cenário educacional, oferecendo uma variedade de benefícios que promovem a comunicação, a aprendizagem personalizada e a inclusão. Com base em pesquisas de especialistas renomados, como Lebedev e Nicolelis, Chaudhary e Antonenko, esta inovação promete revolucionar a forma como aprendemos e ensinamos. A comunicação aumentada proporcionada pela BrainNet permite que os alunos compartilhem informações diretamente entre seus cérebros, facilitando a colaboração e a interação social. Isso é especialmente benéfico para alunos com deficiências de comunicação, como autismo, pois promove a inclusão e reduz o isolamento social. Além disso, a tecnologia BrainNet oferece feedback em tempo real aos educadores, permitindo uma compreensão mais profunda do processo de aprendizagem de cada aluno. Isso possibilita a adaptação da instrução de acordo com as necessidades individuais, garantindo uma experiência educacional mais personalizada e eficaz. No entanto, o uso ético e responsável da BrainNet na educação é crucial. Questões de privacidade dos dados, equidade no acesso e consentimento informado devem ser cuidadosamente consideradas para garantir que todos os alunos se beneficiem igualmente dessa tecnologia inovadora.
A PROTEÇÃO AO TRABALHADOR DOMÉSTICO: UMA ANÁLISE SOBRE AS VIOLAÇÕES NO AMBIENTE DE TRABALHO
Authors: Souza Isabela Farias de , Ferreira Vanessa Rocha
Published: May 2024

O presente artigo propõe a expor os meios de violação aos direitos dos trabalhadores domésticos e discutir o impacto causado na vida desses indivíduos. Trata-se de pesquisa produzida pelo método dedutivo – por meio de exame bibliográfico e teórico-normativo que tem como problema de pesquisa a seguinte pergunta: Em que medida as violações aos direitos dos trabalhadores domésticos impactam na vida desses indivíduos? Na análise, primeiro discute-se a conjuntura histórica que levou a construção do trabalho doméstico no Brasil, bem como a caracterização deste trabalhador dando enfoque a mulher nesse meio. Em seguida, expõe-se a existência e a repercussão do descumprimento às normas jurídicas, recorrentes no local de trabalho, na vida dessas pessoas, com destaque para: o desrespeito a proteção da saúde física e psíquica por meio da sobrecarga de tarefas, desgaste psicológico e discriminação, bem como a problemática resultante da falha no reconhecimento do vínculo empregatício para as empregadas residentes no local de trabalho. Por fim, destaca-se o trabalho doméstico decente como preceito fundamental para tutela efetiva dos direitos das domésticas.
Gendered Differences in Acknowledgements for Doctoral Advisors at a Land-Grant University
Authors: Copenheaver Carolyn , Meacham Thomas , Black Bryan
Published: May 2024

The acknowledgements section of a doctoral dissertation provides a rare view into the student-advisor relationship. The gendered differences for how doctoral students acknowledge male and female advisors was examined in 208 dissertations from a U.S. land-grant university. Doctoral students used a greater number and diversity of words when acknowledging female advisors. Nine hierarchical thematic roles and obligations of advisors were identified and were equally represented in acknowledging male and female advisors. Doctoral students described the roles and obligations of their doctoral advisor independently of gender; however, they used gendered language, which highlights the persistence of gendered norms within academic culture.