Investigation of stress-strain behavior of a sheet material using free bulging test

In this work, a new experimental-numerical technique is developed in order to investigate the constitutive behaviour of a sheet material in conditions of superplastic forming. The principal feature of this technique is that unlike classical tensile testing it allows one to obtain stress-strain curves for a material formed in biaxial tension conditions produced by free bulging process. These conditions are much closer to the ones that the material undergoes during the superplastic forming process. Consequently, they give more accurate information about the material behaviour than the ones coming from tensile tests data. The drawback is that the strain (and similarly its time derivative) cannot be directly measured and controlled during free bulging test but its value has to be derived from other macroscopic measurement. Towards this end, a blow forming machine was equipped with a position transducer for the measurement of the dome height during the test. In order to control the stress in the dome apex at a predetermined level the applied pressure was continuously adjusted to current dome height using a special algorithm. After the test, the dome height data were processed to obtain the evolution of stress, strain and strain rate at the dome apex as well as the stress strain curves for constant referenced strain rates. The tests were performed on superplastic aluminium alloy (ALNOVI-U) sheets of 1.35 mm initial thickness at 500°C. Using the data from two tests with different strain rate paths the stress-strain curves and the strain rate sensitivity index evolution were calculated for two constant referenced strain rates. The obtained constitutive data were verified by finite element simulation of a blow forming

Numerical simulation in roll pass design for bar rolling

The application of finite element simulation to the problem of roll pass design for round bar rolling is considered. Two roll pass sequences were developed by analytical methods and then optimized using 2.5D Finite Element Method (FEM). The first one is a classical oval-round roll pass design. The second one is a combination of flat rolls and round roll passes. Relying on the simulation data obtained by FEM, the roll gaps were adjusted to achieve the required bar shape and the uniform distribution of rolling force between the passes. Advantages and disadvantages of each roll pass design were considered.Web of Science541787

Tecnología para la formación temprana de resistencia al estrés en el sistema de prevención de la mala adaptación escolar de alumnos de primer grado

The relevance of the stated problem of the crisis of 6-7-year old’s is dictated by the recently growing tendency to bring back children to preschool institutions after a short period at school by parents who notice the child’s painful condition associated with school maladaptation. In this regard, many researchers and practicing educators recommend reviewing the start dates for children at school so that the child starts school at the age of seven. Other teachers notice a significant increase in the work load on primary schoolchildren connected to the introduction of the Federal State Educational Standard for Primary General Education and the corresponding forms of control and assessment activities. Thus, there was a need to develop new technologies to preserve the health of younger students and allow them to overcome the crisis of the onset of education. The purpose of this article is to describe the developed technology aimed at helping 6-7-year old to overcome the age crisis and prevent school maladaptation with the help of early formation of stress tolerance. The main method in the study is the design of a technology for early formation of stress tolerance and prediction of the results of its implementation in the experimental groups of 6-7-year-old children. The technology is based on the principles of continuity of the educational process between preschool educational organizations and schools. With the implementation of the developed technology the following results were achieved: increased motivation for success and higher somatic health level manifested in sport and creative activities. The above-mentioned results in their turn contributed to crisis prevention, school deprivation of first graders and comfortable overcoming of the crisis of 6-7 year olds. The materials of the article can be useful to organizers of sport and creative activities in preschool educational institutions, educators of preparatory groups, teachers, methodologists in preschool and primary education, as well as physical education teachers and primary school teachers. The materials of the article can be used in the system of advanced training of teachers of physical education and elementary school, as well as in the preparation for professional activities in preschool educational institutions and elementary schools of students of teacher training colleges and universities.La relevancia del problema declarado de la crisis de los niños de 6 a 7 años está dictada por la tendencia cada vez mayor de traer a los niños a las instituciones preescolares después de un corto período en la escuela por parte de los padres que notan la condición dolorosa del niño asociada con la mala adaptación escolar. En este sentido, muchos investigadores y educadores en ejercicio recomiendan revisar las fechas de inicio de los niños en la escuela para que el niño comience la escuela a la edad de siete años. Otros maestros notan un aumento significativo en la carga de trabajo de los escolares de primaria relacionados con la introducción del Estándar Educativo del Estado Federal para la Educación General Primaria y las formas correspondientes de actividades de control y evaluación. Por lo tanto, era necesario desarrollar nuevas tecnologías para preservar la salud de los estudiantes más jóvenes y permitirles superar la crisis del inicio de la educación. El propósito del artículo es describir la tecnología desarrollada destinada a ayudar a niños de 6 a 7 años a superar la crisis de la edad y prevenir la mala adaptación escolar con la ayuda de la formación temprana de tolerancia al estrés. El método principal en el estudio es el diseño de una tecnología para la formación temprana de tolerancia al estrés y la predicción de los resultados de su implementación en los grupos experimentales de niños de 6-7 años. La tecnología se basa en los principios de continuidad del proceso educativo entre las organizaciones educativas preescolares y las escuelas. Con la implementación de la tecnología desarrollada se lograron los siguientes resultados: mayor motivación para el éxito y un mayor nivel de salud somática manifestado en actividades deportivas y creativas. Los resultados mencionados a su vez contribuyeron a la prevención de crisis, la privación escolar de los alumnos de primer grado y la superación cómoda de la crisis de los niños de 6 a 7 años. Los materiales del artículo pueden ser útiles para los organizadores de actividades deportivas y creativas en instituciones educativas preescolares, educadores de grupos preparatorios, maestros, metodólogos en educación preescolar y primaria, así como maestros de educación física y maestros de primaria. Los materiales del artículo se pueden utilizar en el sistema de formación avanzada de docentes de educación física y primaria, así como en la preparación de actividades profesionales en instituciones educativas preescolares y escuelas primarias de estudiantes de escuelas de formación de docentes y universidades

Atlantic water flow into the Arctic Ocean through the St. Anna Trough in the northern Kara Sea

The Atlantic Water flow from the Barents and Kara seas to the Arctic Ocean through the St. Anna Trough (SAT) is conditioned by interaction between Fram Strait branch water circulating in the SAT and Barents Sea branch water—both of Atlantic origin. Here we present data from an oceanographic mooring deployed on the eastern flank of the SAT from September 2009 to September 2010 as well as CTD (conductivity-temperature-depth) sections across the SAT. A distinct vertical density front over the SAT eastern slope deeper than ∼50 m is attributed to the outflow of Barents Sea branch water to the Arctic Ocean. In turn, the Barents Sea branch water flow to the Arctic Ocean is conditioned by two water masses defined by relative low and high fractions of the Atlantic Water. They are also traceable in the Nansen Basin downstream of the SAT entrance. A persistent northward current was recorded in the subsurface layer along the SAT eastern slope with a mean velocity of 18 cm s−1 at 134–218 m and 23 cm s−1 at 376–468 m. Observations and modeling suggest that the SAT flow has a significant density-driven component. It is therefore expected to respond to changes in the cross-trough density gradient conditioned by interaction between the Fram Strait and Barents Sea branches. Further modeling efforts are necessary to investigate hydrodynamic instability and eddy generation caused by the interaction between the SAT flow and the Arctic Ocean Fram Strait branch water boundary current

Breathing parameters in healthy men and women in supine, sitting, and standing positions

The present study aimed to investigate the relationship between postural stability, external breathing, and sex, as this area of research is not yet well explored. The study included 19 healthy participants, both male and female, and compared their breathing parameters in three positions: sitting, standing, and supine. The objective was to collect data to develop a non-contact method for recording external respiration. The analysis included measurements of vital capacity and forced vital capacity pulmonary tests, as well as parameters of natural breathing. We confirmed that the lung volume component was higher in males than in females in the sitting position. Additionally, postural influence on breathing was observed only in male participants, with no significant impact on females. Men also exhibited an increased respiratory rate in both standing and supine positions, as well as increased minute ventilation when standing as compared to sitting. Furthermore, men demonstrated higher maximum inspiratory and expiratory vital capacities in all positions as compared to women. These results have important implications not only for the development of non-contact methods for recording respiration but also in the studies of vertical stance, in clinical investigations

Superplasticity of Ti-6Al-4V titanium alloy : microstructure evolution and constitutive modelling

Determining a desirable strain rate-temperature range for superplasticity and elongation-to-failure are critical concerns during the prediction of superplastic forming processes in α + β titanium-based alloys. This paper studies the superplastic deformation behaviour and related microstructural evolution of conventionally processed sheets of Ti-6Al-4V alloy in a strain rate range of 10–5–10–2 s–1 and a temperature range of 750–900 °C. Thermo-Calc calculation and microstructural analysis of the as-annealed samples were done in order to determine the α/β ratio and the grain size of the phases prior to the superplastic deformation. The strain rate ranges, which corresponds to the superplastic behaviour with strain rate sensitivity index m ˃ 0.3, are identified by step-by-step decreasing strain rate tests for various temperatures. Results of the uniaxial isothermal tensile tests at a constant strain rate range of 3 × 10−4–3 × 10−3 s−1 and a temperature range of 800–900 °C are presented and discussed. The experimental stress-strain data are utilized to construct constitutive models, with the purpose of predicting the flow stress behaviour of this alloy. The cross-validation approach is used to examine the predictability of the constructed models. The models exhibit excellent approximation and predictability of the flow behaviour of the studied alloy. Strain-induced changes in the grain structure are investigated by scanning electron microscopy and electron backscattered diffraction. Particular attention is paid to the comparison between the deformation behaviour and the microstructural evolution at 825 °C and 875 °C. Maximum elongation-to-failure of 635% and low residual cavitation were observed after a strain of 1.8 at 1 × 10−3 s−1 and 825 °C. This temperature provides 23 ± 4% β phase and a highly stable grain structure of both phases. The optimum deformation temperature obtained for the studied alloy is 825 °C, which is considered a comparatively low deformation temperature for the studied Ti-6Al-4V alloy

Diagnostic of Cystic Fibrosis in Lung Computer Tomographic Images using Image Annotation and Improved PSPNet Modelling

The research deals with the development of an algorithm for detecting pathological formation in cystic fibrosis using the PSPNet model with focal loss. The model allows data sets to be entered in accordance to their similarities based on their pathological diagnostic signs. The simple and effective algorithm structure groups annotated images, processes them in a multiscale CNN, and localizes areas of cystic fibrosis in the lungs with high accuracy

Bacterial number and genetic diversity in a permafrost peatland (Western Siberia): Testing a link with organic matter quality and elementary composition of a peat soil profile

Permafrost peatlands, containing a sizable amount of soil organic carbon (OC), play a pivotal role in soil (peat) OC transformation into soluble and volatile forms and greatly contribute to overall natural CO2 and CH4 emissions to the atmosphere under ongoing permafrost thaw and soil OC degradation. Peat microorganisms are largely responsible for the processing of this OC, yet coupled studies of chemical and bacterial parameters in permafrost peatlands are rather limited and geographically biased. Towards testing the possible impact of peat and peat pore water chemical composition on microbial population and diversity, here we present results of a preliminary study of the western Siberia permafrost peatland discontinuous permafrost zone. The quantitative evaluation of microorganisms and determination of microbial diversity along a 100 cm thick peat soil column, which included thawed and frozen peat and bottom mineral horizon, was performed by RT-PCR and 16S rRNA gene-based metagenomic analysis, respectively. Bacteria (mainly Proteobac-teria, Acidobacteria, Actinobacteria) strongly dominated the microbial diversity (99% sequences), with a negligible proportion of archaea (0.3–0.5%). There was a systematic evolution of main taxa according to depth, with a maximum of 65% (Acidobacteria) encountered in the active layer, or permafrost boundary (50–60 cm). We also measured C, N, nutrients and ~50 major and trace elements in peat (19 samples) as well as its pore water and dispersed ice (10 samples), sampled over the same core, and we analyzed organic matter quality in six organic and one mineral horizon of this core. Using multiparametric statistics (PCA), we tested the links between the total microbial number and 16S rRNA diversity and chemical composition of both the solid and fluid phase harboring the microor-ganisms. Under climate warming and permafrost thaw, one can expect a downward movement of the layer of maximal genetic diversity following the active layer thickening. Given a one to two orders of magnitude higher microbial number in the upper (thawed) layers compared to bottom (frozen) layers, an additional 50 cm of peat thawing in western Siberia may sizably increase the total microbial population and biodiversity of active cells

Ferromagnetic HfO2/Si/GaAs interface for spin-polarimetry applications

In this letter, we present electrical and magnetic characteristics of HfO2-based metal-oxide-semiconductor capacitors (MOSCAPs), along with the effect of pseudomorphic Si as a passivating interlayer on GaAs(001) grown by molecular beam epitaxy. Ultrathin HfO2 high-k gate dielectric films (3–15 nm) have been grown on Si/GaAs(001) structures through evaporation of a Hf/HfO2 target in NO2 gas. The lowest interface states density Dit at Au/HfO2/Si/GaAs(001) MOS-structures were obtained in the range of (6−13)×101