bluuebunny/crossref_metadata_2025 huggingface dataset:
A supplier selection model for the wood fiber supply industry
Authors: Navarro Nicolas , Fallas Valverde Paula Daniela , Quesada Henry Jose , Madrigal-Sánchez Johanna
Published: April 2023

The wood fiber industry has a complex and sensitive supply chain. Consumers and suppliers across the wood fiber supply industry share a highly dynamic relationship, but they lack a structured technique to evaluate and improve the flow of information and materials. The goal of this study was to develop a mathematical model based on supplier selection and assessment criteria using structured, multi-criteria decision-making methods. The first method was the analytic hierarchy process (AHP) and the second method was the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS). These methods were chosen based on their acceptance and use in previous research. The hybrid model was implemented as a software tool based on Microsoft Excel and Visual Basic. The tool improved the way in which wood product firms selected their suppliers and guaranteed that the best available alternatives were selected, thus increasing the chance of a successful supplier-consumer relationship and increasing the value that the company receives from its supplier base. Seven interviews were conducted in the wood fiber industry to validate the tool. The tool was found to be applicable and a valuable approach, as reported by most participants.
Problems encountered in log depots and measures to combat them: A review
Authors: Yalçın Mesut
Published: April 2023

The aim of this review is to examine the problems encountered with logs kept in depots and the measures recommended to correct them. Biotic, abiotic, and other factors can affect the quality and quantitative properties of stored logs. Biotic factors include fungi (decay/rot fungi, stain fungi, and mold), insects (wood, bark, and ambrosia beetles), and bacteria. The climatic conditions of ultraviolet (UV) light, wind, and temperature at the storage site can be considered as abiotic factors. In addition, storage problems may be caused by business management, inadequate training and qualifications of depot personnel, and the type of depot floor/ground. Measures to counteract these factors were examined in detail, as a result of field observations and literature studies. The solutions presented included: shortening the storage period and expanding winter production rather than maintaining year-round storage, bringing production planning in line with the needs of the sector and providing sufficient training to workers and technical personnel, as well as increasing the sale of standing trees, separating earlier- and later-felled products in depot areas, installing pheromone traps, and ensuring proper drainage and maintenance of depot grounds. Additional measures to be taken in factory warehouses included water sprinkling and holding logs in water (ponding).
The Effects of Economic Deterioration Due to COVID-19 to Alcohol and Tobacco Consumption Behaviors of Adolescents in South Korea: A Nationwide Analysis
Authors: Lee JaeHyuck , Hong Seung Wan
Published: April 2023

Coronavirus disease 2019 (COVID-19) pandemic has greatly impacted health, culture, and the economy. Although it has had little direct effect on children and adolescents, its indirect effect on them has been significant. In this study, we aim to evaluate the alcohol and tobacco consumption behaviors of adolescents and the economic determination of their families due to COVID-19.We collected data from the Korea Youth Risk Behavior Survey, which is an annual cross-sectional national representative survey published by the Korea Disease Control and Prevention Agency in South Korea. We considered, in particular, the survey conducted in middle and high school students in 2020.The number of subjects was 54,948 with 28,353 male students and 26,595 female students. The drinking rate was higher in male students and female students in the group with severe economic deterioration compared to the group without deterioration (odd ratio [OR], 1.355; 95% confidence interval [95% CI], 1.175-1.563; OR, 1.199; 95% CI, 0.987-1.457). The smoking rate was higher in male students and female students in the group with severe economic deterioration (OR, 1.435; 95% CI, 1.180-1.745; OR, 1.809; 95% CI, 1.331-2.457). The secondhand smoking rate at home was higher in male students and female students in the group with severe economic deterioration (OR, 1.397; 95% CI, 1.239-1.574; OR, 1.440; 95% CI, 1.263-1.641).The economic deterioration due to COVID-19 is a risk factor for alcohol drinking, smoking, and secondhand smoking among adolescents. Our study results suggest the need to pay more attention to youth health management in the event of sudden economic impacts.
Pneumonia Clinical Features in Under-Five Children Treated in Atma Jaya Hospital in 2017-2020
Authors: Roselany Rachel , Surjono Edward
Published: April 2023

Pneumonia is the leading cause of infection-related death among children and still remains a global health problem, especially for children under five. This study aimed to identify the clinical features of pneumonia in under-five chilren treated at Atma Jaya Hospital during the period of 2017-2020. This was a cross-sectional retrospective descriptive study on all under-five patients diagnosed with pneumonia treated in Atma Jaya Hospital. Data were collected from November 2021-January 2022 from the medical records of these children (n=148) and analyzed using the univariate analysis.  Results showed that most subjects of this study were boys (60.8%), in the age group of 1-4 years old (62.2%), with fever as the most common pnemonia clinical symptom (93.9%). Physical examinations revealed that the average pulse of the subjects were 131.2 beats/minute and the average temperature was 37.1°C. Other signs and symptoms identified during physical examinations were tachypnea (20,3%), retractions (56.1%), crackles (82.4%), and wheezing (22,3%). The laboratory findings presented a mean hemoglobin of 11.0 g/dL, a mean hematocrit of 32.5%, and a mean CRP of 13.2 mg/dL, while most subjects had normal leukocyte (58.1%) and platelet counts (52.0%). The most common chest X-ray finding of pneumonia in these children was infiltrate (92.6%) and the average length of stay was 4 days. Most under-five children experiencing pneumonia recovered after treatment (97.3%).
Programa Inova Educação: a formação do professor
Authors: Silva Renata Kelly da , Andrade Maria de Fátima Ramos de , Mizukami Maria da Graça Nicoletti
Published: April 2023

O presente artigo tem como objetivo analisar as contribuições do “Programa Inova Educação” para o desenvolvimento profissional de professores que atuam no componente curricular “Tecnologia e Inovação” na Secretaria da Educação do Estado de São Paulo. Para a realização do estudo optamos por uma pesquisa de abordagem qualitativa de cunho descritivo-analítico, que utilizou questionário e entrevista como instrumentos para a coleta dos dados. Os principais aportes teóricos que fundamentaram o estudo foram: Marcelo Garcia, Lee Shulman, Antônio Nóvoa, Paulo Freire, Maria da Graça Mizukami, Cochran-Smith e Lytle. Constatamos, com a análise realizada, que apesar dos professores estarem cientes de que seria fundamental ter conhecimento na área de tecnologia para lecionar o componente curricular “Tecnologia e Inovação”, a maioria afirmou que ingressou na disciplina mesmo sem possuir este conhecimento. Além disso, para a maioria, o curso oferecido pela Secretaria da Educação, como pré-requisito para lecionar o componente curricular, não foi suficiente para suprir as necessidades dos participantes.
Algorithm for topology optimization of a structure made of anisotropic material with consideration of the reinforcement orientation parameters
Authors: Fedulov B. N , Fedorenko A. N , Antonov F. K , Lomakin E. V
Published: April 2023

Advanced design methods offer not only a number of methods of modeling structures but also quite profound optimization approaches. The topology optimization is one of such advantageous methods. There are several implementations of this type of structural analysis, but the most common option is to deal with the material density as a generalized parameter. The development of 3D printing technologies increases the interest in algorithms of this type. However, it mostly refers to printing with metal or plastic, which implies the material isotropy. Advances in continuous fiber printing systems and automatic placement machines using composite tapes make it possible for engineers to control not only a material’s position, but also to choose the local orientation of reinforcing elements. Such systems require optimization algorithms taking into account additional parameters characterizing the material anisotropy. In this case the traditional problem of the topology optimization should first be modified for the model of an orthotropic material with restrictions on the value of the angle of rotation of the reinforcement lines along the print path. In this paper, an idea of such a topology optimization algorithm is proposed, which is implemented using the Abaqus finite element modeling facilities, and examples of solving typical problems are considered.
Investigation of the stress-strain state of a hollow cylinder with a coating based on the gradient model of thermoelasticity
Authors: Vatulyan A. O , Nesterov S. A , Yurov V. O
Published: April 2023

The study of the stress-strain state of a thermoelastic hollow cylinder with a homogeneous coating is carried out taking into account the scale effects. Aifantis' one-parameter gradient model is used to account for scale effects. Equilibrium equations and boundary conditions for a composite hollow thermoelastic cylinder are obtained on the basis of the Lagrange variational principle. In comparison with the classical formulation of the problem, additional boundary conditions and conjugation conditions are set for moment stresses and displacement gradients. The dimensionlessness of the task of thermoelasticity has been carried out. Solving the problem of uncoupled thermoelasticity begins with finding the radial temperature distribution of a layered cylinder on the basis of solving the problem of heat conduction in the classical formulation. The solution of the problem in displacements is presented as a sum of solutions in the classical formulation of the problem and additional boundary layer terms found on the basis of the asymptotic properties of the modified Bessel functions. Simplified analytical expressions are obtained for finding radial displacements, radial and circumferential Cauchy stresses, nonzero components of the tensor of moment and total stresses. On specific examples, calculations of the radial distribution of displacements and stresses of a composite cylinder in the case of both mechanical and thermal loading are carried out. The limits of applicability of the asymptotic solution of the problem are investigated. The difference between the radial distribution of displacements and stresses found on the basis of solutions to the problem in the classical formulation and in the gradient formulation is shown. It was found that the Cauchy radial stresses experience a jump at the boundary of the cylinder and the coating, which is explained by the continuity of radial displacements and their first derivatives. The components of the moment stress tensor either take on peak values or experience a jump at the interface. The moment stresses are proportional to the square of the gradient parameter, at small values of which they have values that are much less than the values of the total stresses. With an increase in the dimensionless scale parameter, the values of radial displacements and total circumferential stresses decrease, but moment stresses increase.
Multilevel model of polycrystals: application to assessing the effect of texture and grains misorientation on the critical deformation of the dynamic recrystallization initiation
Authors: Kondratev N. S , Trusov P. V , Podsedertsev A. N
Published: April 2023

The current state of materials constitutive models and the computer technology development make it possible to numerically implement complex multilevel models that allow describing the material structure evolution. In this regard, it is possible to formulate optimal control problem for metal forming processes in order to create the required performance characteristics of finished products and their ingots. To solve this problem in this study, the effective multilevel modeling approach is used to describe the thermomechanical treatment of polycrystalline materials. The model is based on this approach with the introduction of internal variables, in which the carriers and physical mechanisms of the processes of hot intense plastic deformation are explicitly considered. At deformation temperatures order of 0.5 homologous and above, recrystallization process have a special effect on the formation and change of the grain and defect material structure. The paper considers the problem of determining the critical deformation of dynamic recrystallization initiation, that depending on the material texture and the mutual misorientation of neighboring grains. Numerical experiments of the multilevel model are used to simulate two stages of inelastic deformation for this purpose. At the first stage, cold inelastic deformation by simple shear and compression is considered, that leading to the formation of a corresponding texture. At the second stage, uniaxial hot tension deformation is considered. The initial distribution of crystallographic grain orientation is assumed to be uniform. Two variants of the grains mutual misorientation with the prescribed increased and decreased values of the average misorientation angles are considered. The recrystallization process is not explicitly modeled. The current model is intended to assess the recrystallization critical deformation. It is shown that the mutual misorientation of grains, rather than texture, has the most influence on the critical deformation. An increase in the angle of grains mutual misorientation contributes to an earlier start of the dynamic recrystallization process. The formation of a deformation texture leads to a decrease in the angle of mutual misorientation, and, accordingly, to a decrease in dynamic recrystallization intensity. Despite this, with an increase of deformation, the driving force of recrystallization (the average value of the difference of stored energy between neighbor grains) is increases, which leads to the implementation of dynamic recrystallization.
Numerical modeling of natural vibrations of coaxial shells partially filled with fluid, taking into account the effects on the free surface
Authors: Bochkarev S. A , Lekomtsev S. V , Senin A. N
Published: April 2023

This work is devoted to the numerical analysis of vertical elastic coaxial cylindrical shells completely or partially filled with a quiescent compressible fluid with account for sloshing of its free surface. The problem is solved in the axisymmetric formulation using a semi-analytical version of the finite element method. The fluid medium is described by the wave equation, which together with the conditions prescribed at its boundaries is reduced to the weak form by the Bubnov - Galerkin method. A mathematical formulation of the dynamic problem for thin-walled structures is developed using the variational principle of virtual displacements and linear theory of thin shells based on Kirchhoff - Love hypotheses. The fluid pressure on the walls of the structure is calculated according to Bernoulli's equation. Sloshing modes caused by gravitational effects on free surface of liquid medium are excluded from the resulting system of equations through the use of the iteration dynamic condensation method. The numerical model has been verified by comparing it with the known data for the case of a single shell partially filled with fluid. The influence of the fluid level on the lowest natural frequencies of the system vibrations at different variants of kinematic boundary conditions for shells (rigid clamping at both edges, cantilever support) and different widths of the annular gap between them has been evaluated. It has been found that for the examined configurations, the level of the fluid in the annular channel has a stronger influence on the frequency spectrum compared to the level of fluid in the cavity of the inner shell due to the fact that vibration frequencies change in a wider range.
The method of fictitious discrete models in calculations of composite bodies
Authors: Matveev A. D
Published: April 2023

As is known, the calculation of the static strength of elastic composite bodies (CB) is reduced to finding the maximum equivalent stresses for these bodies. The finite element method (FEM) is widely used for the analysis of the stress state of CB. The basic discrete models (BM), which take into account the inhomogeneous structure of bodies in the framework of a micro-approach, have a high dimension. To reduce the dimension of discrete models, multigrid finite elements (MgFE) are effectively used. However, there are BM CB (for example, BM bodies with a micro-homogeneous structure), which have such a high dimension that the implementation of FEM for such BM using MgFE, due to limited computer resources, is difficult. To solve this problem, it is proposed to use fictitious discrete models whose dimensions are less than the dimension of the BM CB. In this paper, we propose a method of fictitious discrete models (MFDM) for calculating the strength of elastic bodies with an inhomogeneous, micro-homogeneous regular structure. The proposed method is implemented using FEM with the use of MgFE and adjusted strength conditions that take into account the error of approximate solutions. The method is based on the position that the solutions that meet the BM CB differ little from the exact ones. The calculation of CB according to MFDM is reduced to the construction and calculation of the strength of fictitious discrete models (FM), which have the following properties. The FM reflects: the shape, characteristic dimensions, attachment, loading and type of the inhomogeneous structure of the CB, and the distribution of elastic modulus corresponding to the BM CB. The FM dimension is less than the BM dimension of the CB. The sequence consisting of FM converges to BM, i.e. the limiting FM coincides with BM. The convergence of such a sequence ensures uniform convergence of the maximum equivalent voltages of the FM to the maximum equivalent voltage of the BM. Two types of FM are considered. The first type of FM consists of scaled discrete models, the second type consists of FM with variable characteristic dimensions. Calculations show that the implementation of FEM for FM using MgFE leads to a large saving of computer resources, which allows the use of MFDM for bodies with a micro-homogeneous regular structure. The calculation of the strength of CB according to MFDM requires times less computer memory than a similar calculation using BM CB, and does not contain a procedure for grinding BM. The use of adjusted strength conditions allows us to use approximate solutions with a large error in the calculations of CB for strength, which leads to an increase in the efficiency of MFDM. The given example of calculating the strength of a beam with an inhomogeneous regular fibrous structure according to MFDM shows its high efficiency.
ON THE CONVEXITY OF POTENTIAL OF NONLINEAR ELASTIC MEDIA MODEL WITH TENSOR DAMAGE PARAMETER
Authors: Panteleev I. A , Lyakhovsky V.
Published: April 2023

For solving problems of the theory of elasticity using nonlinear models, the question of the convexity of the potential used and the proof of the uniqueness of the solution are of decisive importance. The present work is devoted to the determination of conditions for the local strict convexity of the potential for the nonlinear elasticity model, which ensure the uniqueness of the solution to the problem in a sufficiently small neighborhood of the desired solution. The considered model is a generalization of a scalar nonlinear rheological model of brittle solid deformation for the case of the tensor damage parameter, the principal values of which describe the reduction in the cross-sectional area of the material in three orthogonal directions. An additional term of the second order in deformation in the elastic potential makes it possible to describe the dependence of the elastic moduli on the type of the stress-strain state, the dilatancy of the material under shear deformation, as well as the nonlinear deformation response even at low loads. The introduced damage tensor of the second rank makes it possible to describe the damage-induced anisotropy of the elastic properties of the material. Conditions of local strict convexity in the principal axes of the strain tensor are obtained in this work for the general case of misaligned strain and damage tensors. To illustrate the obtained convexity conditions, two special cases of the damage tensor type are considered: a transversely isotropic fractured medium with coaxial strain and damage tensors, and a transversely isotropic medium with obliquely oriented fracturing. For both cases, the dependence of the limiting values of damage on the parameter of the degree of anisotropy is shown. It is shown that in the case of weak damage anisotropy, the potential convexity conditions for the scalar damage parameter give a minorant estimate of the maximum allowable damage for various types of stress-strain state. For obliquely oriented fracturing, the dependences of the maximum permissible damage on the degree of anisotropy, the angle of inclination and the type of stress-strain state are plotted.
Evolution of the grain structure of metals and alloys under severe plastic deformation: continuum models
Authors: Trusov P. V , Ostanina T. V , Shveykin A. I
Published: April 2023

Products made of metals and alloys with a fine-grained structure, which have high physical, mechanical and operational characteristics, are becoming increasingly in demand in many technical and technological fields. The most common and efficient technologies for the production of parts from this class of materials are various processes of severe plastic deformation (SPD) (in general practice, at low homologous temperatures). At the same time, to achieve high degrees of deformation, a significant part of metals and alloys require increased processing temperatures, undergo significant heating during deformation processes, which may be accompanied by changes in the grain and subgrain structure due to recovery and recrystallization processes. An empirical approach to the development of SPD modes that ensure the formation of the necessary grain structure requires huge time and financial costs, and therefore considerable attention is paid by researchers in the field of solid mechanics and metal forming to approaches and methods of mathematical modeling. In connection with the foregoing, the number of publications on this subject has been intensively growing in recent years. The currently known models differ significantly in their approaches, the depth of penetration into the physics of processes, and the scope of consideration. The proposed brief review is focused on a qualitative analysis of works on this topic, a preliminary classification of existing models according to their purpose, versatility, and functionality. It seems possible to single out the two most common approaches to describing the change in the grain structure in the processes of thermomechanical processing of metals and alloys: continual (in most cases, single-level) and multilevel, based on the introduction of internal variables and physical theories. This review is devoted to the consideration of publications focused on the first of these approaches. Until now, the most common are macrophenomenological continuum models based on the analysis of experimental data conducted both in laboratories on macrosamples and in real production conditions. Models of this class are usually formulated in the form of operator relations over field quantities, they are relatively easy to implement due to their easy “embedding” into widely used commercial software packages, but they require significant costs for experiments to identify models, they are characterized by a low degree of versatility. Continuous theories are relatively less common, but still often used. These theories are based on the description of physical mechanisms and the evolution of the structure of metals and alloys in terms of continuum variables.
Energy conditions for the formation of magnesium hydride
Authors: Aptukov V. N , Skryabina N. E , Fruchart D.
Published: April 2023

In the present article we consider a novel approach to analyze the processes and kinetics of transformation of magnesium to hydride. Here approach consists to take into account the contributions of mechanics factors such as the work of external forces, the energy of elastic deformation and the energy required to form a unit volume nucleate of new phase. Request for a stable state of either a mechanical system or thermodynamic conditions governing a phase transformation, is to determine a minimum value to the total energy of the system. Analyzing the stability conditions needed when forming a metal hydride nucleus at constant temperature and pressure needs to consider the following: - the volumetric effects at the phase transformation, - the ratio of elastic moduli of metal to hydride phase, - the work spent at the formation of a unit volume of hydride. Under these considerations, it was shown that the most energetically favorable is forming an ellipsoidal hydride nucleus. Moreover, the larger difference in semi-axes, the more stable ellipsoid nucleus. Then, calculations of the stress-strain level states on both sides of the metal/hydride interface have been carried out. It was shown that the near-boundary range during the phase transformation is the place where accumulate inhomogeneous and intense stresses, which can contribute to two parallel processes. Firstly, increase of hydrogen concentration could appear in the distorted area. Secondly, a local accumulation of incoherent boundaries in between the two phases will develop stresses exceeding by more twice the shear yield stress. The presence of these compression zones could give rise new defects such as dislocations, micro-cracks. Consequently this should lead to decrease in magnitude of the powder of material.
Analysis of the limiting states of cylindrical elastic-plastic shells under tension and combined loading by internal pressure and tension
Authors: Bazhenov V. G , Kazakov D. A , Osetrov S. L , Osetrov D. L , Ryabov A. A
Published: April 2023

The elastic-plastic deformation, limiting states and supercritical behavior of cylindrical shells under tension and combined loading by internal pressure and tension to failure are studied theoretically and experimentally. This problem is characterized by the occurrence of large strains, shape changes and, as a result, an inhomogeneous stress-strain state. In the numerical solution of such problems, the problem arises of constructing true stress-strain curves of materials. In this regard, to study the deformation and strength properties of materials, it is important to use an experimental-computational approach, which makes it possible to take into account the non-uniaxiality and inhomogeneous of the stress-strain state without accepting simplifying hypotheses. The paper presents a new efficient algorithm for constructing a true stress-strain curve, which is based on the procedure of nonlinear extrapolation of the curve. Such an algorithm, in the process of direct numerical solution of the problem, consistently constructs a stress-strain curve without using repeated direct calculations, which significantly (at times) increases its efficiency. Based on the experimental-computational approach, the true stress-strain curves for solid rods and shells made of 10KhSND and 10G2FBYu steels were determined under tension and combined loading by internal pressure and tension to failure. The failure of shells under tension occurs at lower (at times) values of true strain than solid rods. Significant differences in true stresses and strains at the moment of failure are due to different localization of deformation of solid rods and shells after the loss of stability of plastic deformation in tension. It is shown numerically and experimentally that after loss of stability of plastic deformation according to Considerer in tension, the cylindrical shell contains two forms of loss of stability until the moment of failure. The first form of loss of stability, as in solid rods, is characterized by localization of deformations along the diameter of the sample in the form of a neck, and the second form is characterized by localization of deformations along the thickness of the sample, which determines the final stage of failure. Under the action of internal pressure on the shell, the first form of loss of stability of plastic deformation degenerates with the formation of a neck inside the shell, and only the form of loss of stability is observed, caused by the localization of deformations along the thickness of the shell.
Implementation of the Lemaitre damage model with kinematic hardening in the ANSYS finite element complex
Authors: Fedorenkov D. I , Kosov D. A
Published: April 2023

Currently, one of the most popular in fracture mechanics is taking into account damage and its effect on the stress-strain state of structural elements. In this work, the Lemaitre damage model was integrated taking, into account the combined hardening law, which combines the Armstrong - Frederick kinematic hardening law and the Voce isotropic hardening law, into the ANSYS finite element software. The model is implemented in the form of a dynamically linked library of user material for three-dimensional objects, which is tested on a cylindrical specimen with an external annular notch, both in an axisymmetric setting and in a three-dimensional one. The article presents model representations of the above-listed standard systems. This work demonstrates only one of the two stages of verification of the created program - comparison of damage fields under monotonic loading with data known in the literature - and doesn’t take into account the verification of cycle-by-cycle kinetics of plastic deformation accumulation with experimental data for low-cycle fatigue. The result of verification, consistent with similar experiments known in the literature, is confirmed in accordance with similar experiments. In addition, an analogy was found using the TSL law of the cohesive fracture mechanics approach. Despite the fact that two different types of constitutive equations are used in the cohesive model and Lemaitre, the physical meaning of these equations consists in one thing - visualization and identification of mechanisms and coordinates of damage.
EVALUATION OF THE THERMAL AND MOISTURE AGING INFLUENCE IN AGGRESSIVE ENVIRONMENTS ON THE CHANGE IN THE OF THE MECHANICAL BEHAVIOR OF FIBERGLASS BY A SHORT BEAM BENDING TESTS BASED ON ACOUSTIC EMISSION TECHNIQUE
Authors: Lobanov D. S. , Lunegova E. M.
Published: April 2023

The work is aimed at experimental research and description of the mechanical behavior and degradation of the fibrous structural composite material strength properties during thermal and moisture aging in aggressive (operational) environments of different duration and temperatures. The object of the study was STEF structural fiberglass. STEF is a laminated fiberglass reinforced plastic obtained by hot pressing of glass fabric impregnated with a thermosetting binder based on combined epoxy and phenol-formaldehyde resins. After preliminary aging under various temperature-time conditions, fiberglass samples were tested at normal temperature for interlayer shear. To study the defect initiation and propagation during the deformation of fiberglass after preliminary aging under various temperature-time conditions and environments, the acoustic emission method is used in this work, which makes it possible to study the deformation stage structure and track the processes associated with the formation of defects in the structure of the fibrous composite. Influence of various media, such as industrial water, sea water and machine oil, at different durations (15, 30, 45 days) and temperatures (22°, 60° и 90 °С) on the processes of composite destruction and the implementation of various mechanisms damage accumulation during quasi-static interlaminar shear tests were obtained and analyzed. The paper presents the test results obtained by the acoustic emission signals processing. The data illustrating the stages of damage accumulation are presented and described, and the main mechanisms of damage to the composite structure under loading are analyzed. The results of a study of the microstructure of samples obtained using a stereomicroscope before and after thermal and moisture aging in aggressive media are described.
ANALYSIS OF MESOSTRUCTURE AND FRACTURE KINETICS OF ELEMENTS OF LATTICE COMPOSITE STRUCTURES UNDER TRANSVERSAL COMPRESSION USING STOCHASTIC FEA MICROMECHANICS
Authors: Sapozhnikov S. B. , Shaburova N. A. , Ignatova A. V. , Shanygin A. N.
Published: April 2023

The paper analyses the mesostructure of the structural elements of lattice aircraft shells – ribs consisting of alternating layers of equal thickness and made from unidi-rectional CFRP and pure matrix material. In experimental studies, the elastic characteristics of unidirectional CFRP were obtained under three-point bending and transversal compression. As a result, the longitudinal modulus of elasticity of the layered composite turned out to be 101 GPa, and the shear modulus was 2.95 GPa. Numerical modeling of the meso- and micromechanics of the interaction of the noticed layers under transversal compression has been performed up to failure. The ANSYS FEA software (explicit and implicit formulations) was used. The regular and stochastic stacking of fibres in the cross section under compression is considered. The fiber diameters in the composite element were measured on thin sections using a Zeiss Axio Observer D1m digital microscope and were equal to 5.1 ± 0.8 µm. Layers with a fiber volume fraction of about 60 % alternate with layers of pure epoxy. It is proposed to use only the first principal stress in the matrix as a micromechanical criterion for failure under com-pression and tension. At the first stage of calculations, the problem of transversal compression of a cell with a regular laying of fibres was solved (the error in the value of the transversal modulus of elasticity was less than 2 %). At the second stage, an assessment was made of the strength and accumulation of microdamages under compression in a model of a layered structure with stochastic fibre stacking. The analysis of stress-strain state of a layered mesostructure under compression made it possible to explain the reason that the rib has a trans-verse strength twice lower than that of a homogeneous CFRP. The calculated values of the ultimate strength in transversal compression of a layered rib are in good agreement with the experimental ones.
PREDICTION OF THE BEARING CAPACITY OF THE HIP JOINT ENDOPROSTHESIS FROM THE С/C COMPOSITES
Authors: Razumovskii E. S. , Shavshukov V. E. , Anoshkin A. N.
Published: April 2023

The article evaluates the bearing capacity of the hip joint endoprosthesis made of carbon/carbon (С/C) composites under anatomical load. С/C is made on the basis of carbon fiber Ural N/400-22 and phenolformaldehyde resin novolachny type RP-010. A significant complexity in modeling an endoprosthesis is the prediction of the properties of С/C. The complexity of mathematical modeling based on the mechanics of composite materials consists in the impossibility of experimentally determining the mechanical characteristics of a pyrocarbon matrix. The pyrocarbon matrix does not exist in its pure form separately from the composite material. The mechanical characteristics of the С/C are calculated, mathematical models of bone tissue and endoprosthesis are constructed, taking into account the complex composite structure. The femur is represented by a combination of cortical and spongy tissue. The femur in the study was fixed along the lateral and medial condyles of the femur. This fixation corresponds to the contact spot of the condyle with the lateral and medial menisci. The hypothesis is confirmed that the weakest component in the С/C is the pyrocarbon matrix. The position of the highest values of normal and tangential stresses are revealed. The position of concentration of tangential stresses coincide with the areas of destruction of the endoprosthesis during compression testing, which were previously visually identified. New design and technological requirements for the structure have been identified, which will contribute to increasing the reliability of the endoprosthesis.
Editorial
Authors: Crippa Anelise
Published: April 2023

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IMPLEMENTING GAMIFIED VOCABULARY LEARNING IN ASYNCHRONOUS MODE
Authors: Waluyo Budi , Tran Hoang Minh
Published: April 2023

Gamified online quizzes have gained popularity for their potential in enhancing student learning motivations, creating engaging lessons, and improving learning outcomes. Yet, its application and effectiveness in support of student vocabulary learning have only been explored in synchronous learning setting. This study, hence, extended the exploration by examining the implementation of gamified vocabulary learning in an asynchronous mode and analyzing the impacts on students’ learning outcomes in class. The study was carried out for 10 weeks, involving 300 2nd year students at a Thai university. The instrument and measure comprised 500 English academic words made into 10 vocabulary sets on Quizizz.com, and 10 in-class vocabulary tests. The findings of the study revealed that students’ vocabulary learning practice in asynchronous mode had positive correlations with and could significantly predict their in-class vocabulary results. Female students outperformed male students; nonetheless, there was no significant difference across academic majors.
Low Bone Mineral Density, Sedentary Lifestyle, and Depression as Risk Factors for Frailty Syndrome at a Home Care Facility in West Jakarta, Indonesia
Authors: Handajani Yvonne Suzy , Subagya Jonathan Christianto , Widjaja Nelly Tina
Published: April 2023

Background: The life expectancy in Indonesia is increasing. The rising number of the elderly people plays a vital role for a country to achieve development success. However, it has many consequences in the health sector, including a frailty syndrome. This study aimed to explore the association between frailty and related factors.Methods: This cross-sectional study was conducted at a home care facility in West Jakarta between September and October 2019, using a simple random sampling method. Data were analyzed using the chi-square test and multivariate logistic regression. The inclusion criteria were members of the home care aged ≥60 years and had signed a written informed consent.Results: In total, 97 respondents were included. Female gender and bone mineral density (BMD) were associated with frailty syndrome (p=0.018 and p=0.05, respectively). Multivariate logistic regression analysis showed the odds ratio of frailty for the female gender (OR= 3.319; 95% CI 1.045–10.543), low bone mineral density (OR= 4.939; 95% CI 1.516–16.090), depression (OR= 7.622; 95% CI 1.246 – 46.621), and low physical activity (OR = 3.639; 95% CI 1.096 – 12.079).Conclusions: There is a relationship between female gender and bone mineral density with frailty syndrome with the risk factors for frailty syndrome in this study are female gender, low bone mineral density, depression, and low physical activity.
Level of Knowledge, Attitude, and Behavior among Specialists of Otorhinolaryngology-Head and Neck Surgery in West Java Towards Cochlear Implants
Authors: Ramadhanti Annisa , Lasminingrum Lina , Mahdiani Sally , Dermawan Arif , Purwanto Bambang
Published: April 2023

Background: Hearing loss and deafness are still an issue in Indonesia, especially in West Java, with a prevalence of 2.5% and 0.06%, respectively. Cochlear implants are intended for patients with severe sensorineural hearing loss to stimulate the remaining auditory nerves. Based on their competency standards, Otorhinolaryngology-Head and Neck Surgery (ORL-HNS) Specialists are expected to be able to inform patients and families about the cochlear implantation procedures. This study aimed to explore the level of knowledge, attitudes, and behavior of ORL-HNS Specialists in West Java towards cochlear implants.Methods: This study was a descriptive study with a cross-sectional approach. Primary data were collected through a questionnaire filled out by ORL-HNS Specialists who were actively working in West Java in 2021–2022.Results: Data from 157 specialists showed that 41.4% (n=65) had good knowledge about cochlear implants, and 43.9% (n=69) had adequate knowledge, however, 62.4% (n=98) showed a negative attitude. In addition, 99.3% (n=156) showed good behavior.Conclusions: ORL-HNS Specialists in West Java have a sufficient level of knowledge, negative attitude, and good behavior towards cochlear Implants. The negative attitude of the specialists need to be bettered, updating their knowledge about how cochlear implants work and their effectiveness for patients with hearing impairments might give them a new perspective and hopefully change their attitude towards cochlear implants.
Characteristics of Nasal Foreign Body Cases in Dr. Hasan Sadikin General Hospital Bandung
Authors: Hampry Henzen Ghesan , Ratunanda Sinta Sari , Sudiro Melati , Wijana Wijana , Saputri Ayu Hardianti
Published: April 2023

Background: Nasal foreign bodies are caused by the insertion of an extraneous substance into the nasal cavity. These cases frequently occur in children. Nasal foreign bodies are easily diagnosed, yet the treatment may be burdensome with possible complications and costly management. The study aimed to evaluate the characteristics of nasal foreign body cases.Methods: The study was descriptive and cross-sectional, using secondary data taken from all medical records of the Emergency Room in Dr. Hasan Sadikin General Hospital, Bandung, from 2018 to 2021. Data were presented in tables.Results: Of the 57 cases, most of the patients (64.9%) were aged 3-5 years, with boys as the most prevalent cases (59.7%) and the most common complaint was pain (31.7%). Inorganic foreign bodies (61.4%) were more commonly found, and being frequently found in the right nasal cavity (49.1%). The duration of the foreign body in the nasal cavity and the treatment conducted on the patients were mostly not written in the medical records, however, no complications were found.Conclusions: A higher incidence of nasal foreign bodies can be found in boys aged 3-5 years. Inorganic objects and pain are the most common manifestations, although the condition of all patients has been improved. Raising awareness about foreign body cases to the community, especially the parents, is the key to preventing these cases from occurring.
ROOT CAUSE OF AN UNCOMMON ELECTRONIC DETONATOR FAILURE
Authors: Yang Ruilin , Hummel Dirk , Nguyen Tuan
Published: April 2023

Detonator failures during a blast are deemed unsafe and can disrupt the productivity of a project. Therefore, it is desirable to understand the origin of such an event when it happens. A commonly observed detonator failure during blasting is the crushing of the detonator shell due to excessive dynamic pressure from previously fired neighboring blastholes. In a tunneling site in Japan, it was found that detonators failed to initiate with their shells and primary explosive intact. However, their capacitors were discharged due to some damage to the application-specific integrated circuits. This type of detonator failure is distinctly different from more commonly observed failures. Such incidents have not been reported elsewhere. Various measures were conducted to diagnose the problem at the site. This paper formulates a theory that can explain the observed detonator failure and predict the measurements and observations. The theory was initially discovered in a laboratory setting some 60 years ago and is based on the electromagnetic pulse (EMP) generated when detonating the explosive charge. In this work, the EMP generated by an explosive charge in rock was not investigate nor were the EMP characteristics and EMP generated during blasting studied. Rather, this study involved applying a hypothesis to predict an uncommon occurrence of electronic detonator failure, which subsequently led to a successful redesign of the aforementioned detonator circuit and eliminated
the detonator failure issue.
Occurrence, Biological and Enzymatic Activities of Agaricomycetes from the Brazilian Amazon - A Systematic Review
Authors: da Costa Maria Rosiane Lima , Santos Geyse Souza , Peters Leila Priscila , Carvalho Clarice Maia
Published: April 2023

Agaricomycetes are highlighted for producing a variety of compounds and enzymes with nutritional and medicinal properties. However, the knowledge of the diversity of this group of fungi is still insufficient, as well as their biological and enzymatic activities. Thus, the objective of this work is to describe the occurrence, biological and enzymatic activities of Agaricomycetes from the Brazilian Amazon. The present study is a systematic review with the literature search done in the following databases: Scielo, Google Scholar, PubMed and ScienceDirect. The descriptors used were Basidiomycota, Agaricomycetes, mushroom, antimicrobial activity, antitumor activity, antioxidant activity, anti-inflammatory activity, immunomodulator, enzymatic activity, and Brazilian Amazon. We used as inclusion criteria articles in Portuguese and English, published between 2010 and 2021 and that had the full text available and presented relevance to the exposed topic, and as exclusion criteria, works not done in the Brazilian Amazon, duplicate articles in the databases search or outside the topic under study. A total of 40 articles, published between 2010 and 2021, were selected for analysis. 230 species of Agaricomycetes fungi were described for the Brazilian Amazon, with the most frequent orders being Polyporales (52.60%), Agaricales (14.35%), and Hymenochaetales (13.91%). Six studies were found on antimicrobial activity for promising Agaricomycete fungi against the bacteria Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus and the fungi Candida albicans, C. parapsilosis and C. tropicalis. For the antioxidant activity, a study described the species Lentinus citrinus with high amounts of antioxidant compounds. For enzymatic activity, five studies reported Agaricomycete fungi producing protease, cellulase, amylase, pectinase, laccase, and xylanase enzymes. This review shows the scarcity of studies on the description and technological potential of Agaricomycetes from the Brazilian Amazon, highlighting the need to encourage the study of this group of organisms.