Based on experimental data on the combined loading of an infinite layer weakened by a circular hole in a brittle material, its critical state, determined by the energy criterion, is modeled. ...The failure criterion is related to the free energy flow through the interaction arc and the linear size. The proposed approach allows us to reflect the dependence of the critical external load on the radius of curvature. A procedure for determining the value of the linear size is proposed and implemented. Using known experimental results, an estimate of the introduced linear parameter for a layer of GVVS-16 gypsum was obtained.
Fracture of the adhesive layer (AL) of finite thickness with elastoplastic properties in a layered composite is considered in this article. The expression of the
J
C
-integral is obtained as the sum ...of values of the products of the layer thickness and the increments of the specific free energy and specific dissipation. Based on the variational formulation, a solution to the model problem of shear action on a thin elastoplastic layer is obtained. From the analysis of the solution obtained, it follows that in the case of a layer degenerating into a mathematical section, the main contribution to the representation of the
J
C
-integral is made by the term responsible for the energy dissipation, and the energy product tends to zero. In this case, it is not pure dissipation that is considered, this is the product of specific dissipation and layer thickness. The expression of the
J
C
-integral is obtained in terms of the quantities measured in a possible experiment.
•A universal representation of the specific surface energy was found.•A fracture criterion containing a LP is proposed.•The existence of a threshold value of the LP was established.
The authors of ...the article considered a fracture model with a linear parameter (LP) associated with the thickness of the physical cut and the interaction layer (IL) on its continuation. With a zero value of the LP, the fracture model takes a form of a mathematical cut. The initial state of the body corresponds to the initial free binding energy, which is assumed to be negative. By the means of thermomechanical analysis of the fracturing processes, the authors established universal representation of the surface energy, which is valid for both physical and mathematical cuts. In the case of a physical cut, the surface energy is expressed as a product of multiplication of the LP value by the change in the specific free binding energy of the IL. It is called the energy product (EP). Using the proposed formulation, the authors considered the effect of decreasing LP on the critical state of samples of finite dimensions.
Finite deformation of a panel under the influence of pressure is considered. The statement of the problem in displacements with equilibrium conditions represented via true stresses in Lagrangian ...coordinates is proposed. It is proven that the initial equations are satisfied when the panel is uniformly curved during deformation. The use of the previously proposed defining relation makes it possible to determine a differential relationship of the laws of pressure and curvature with time at an arbitrary strain rate. Ideally plastic and superplastic deformations are considered. The dependences of pressure on the curvature and strain time are obtained at which superplasticity occurs. It is revealed that, in this case, the range of stable changes in the curvature does not depend on the strain rate, and the threshold stress does not affect the time it takes to reach a given curvature of the panel.
Summary
Sites in the West Siberian peat bog ‘Bakchar’ were acidic (pH 4.2–4.8), low in nutrients, and emitted CH4 at rates of 0.2–1.5 mmol m−2 h−1. The vertical profile of δ13CH4 and δ13CO2 dissolved ...in the porewater indicated increasing isotope fractionation and thus increasing contribution of H2/CO2‐dependent methanogenesis with depth. The anaerobic microbial community at 30–50 cm below the water table produced CH4 with optimum activity at 20–25°C and pH 5.0–5.5 respectively. Inhibition of methanogenesis with 2‐bromo‐ethane sulphonate showed that acetate, phenyl acetate, phenyl propionate and caproate were important intermediates in the degradation pathway of organic matter to CH4. Further degradation of these intermediates indicated that 62–72% of the CH4 was ultimately derived from acetate, the remainder from H2/CO2. Turnover times of 2‐14Cacetate were on the order of 2 days (15, 25°C) and accounted for 60–65% of total CH4 production. Conversion of 14CO2 to 14CH4 accounted for 35–43% of total CH4 production. These results showed that acetoclastic and hydrogenotrophic methanogenesis operated closely at a ratio of approximately 2 : 1 irrespective of the incubation temperature (4, 15 and 25°C). The composition of the archaeal community was determined in the peat samples by terminal restriction fragment length polymorphism (T‐RFLP) analysis and sequencing of amplified SSU rRNA gene fragments, and showed that members of Methanomicrobiaceae, Methanosarcinaceae and Rice cluster II (RC‐II) were present. Other, presumably non‐methanogenic archaeal clusters (group III, RC‐IV, RC‐V, RC‐VI) were also detected. Fluorescent in situ hybridization (FISH) showed that the number of Bacteria decreased (from 24 × 107 to 4 × 107 cells per gram peat) with depth (from 5 to 55 cm below the water table), whereas the numbers of Archaea slightly increased (from 1 × 107 to 2 × 107 cells per gram peat). Methanosarcina spp. accounted for about half of the archaeal cells. Our results show that both hydrogenotrophic and acetoclastic methanogenesis are an integral part of the CH4‐producing pathway in acidic peat and were represented by appropriate methanogenic populations.
Abstract
The paper deals with the problem of the formation of professional skills in web development. The task is solved through the use of real technical tasks for the implementation of websites in ...teaching, the inclusion in the curriculum of the educational program of the disciplines “Methods and tools for designing information systems”, “Programming network databases” and “Web programming”. The developed methodology was tested at Sholom-Aleichem Priamursky State University, Osh State University, Pacific National University and North-Eastern Federal University during the 2019-2020 and 2020-2021 academic years. 42 students of the direction “Information systems and technologies” took part in the training. The content of the disciplines included obligatory project team work on an assignment from an industrial partner. An important element of preparation was the final exam conducted in the format used in WordlSkills championships. The developed websites were assessed by independent qualified third-party experts in the following areas: work organization and management, communication and interpersonal skills, design and layout, server and client-side programming, database and web portal design. As a result, 74% of students implemented the web portal and submitted the project on time. As a result of passing disciplines and implementing web portals, students studied the principles of rapid development of web systems, received professional competencies and interaction with real organizations.
A model of a physical section that describes stress–strain states in elastic–plastic solids weakened by cracks is proposed. The problem of plane deformation and the stress state of a solid of an ...infinite size of an arbitrary geometry, weakened by a physical section, is solved. It comes down to a system of two variational equations with respect to displacement fields in the parts of the solid bordering the interaction layer. For a material whose properties are close to those of a D16T alloy, the linear parameter introduced into the crack model is estimated, and the critical conditions of solids with lateral cracks in the case of a normal detachment are determined.
Abstract
The study designs and implements a multi-dimensional relational database of fire danger metrological information, as well as areas with vegetation. During conceptualization, OLAP algorithms ...are taken into account as applied to the selection of long-term meteodata and their mathematical processing presented by multidimensional hypercubes. When designing the SQL structure, a layered architecture of geographic information system (GIS) is used, including attribute and geographical characters. The data according to the technology is tested in the Jewish Autonomous Region. The database contains metrological information from five weather stations from 1960 to 2020 and five branches of local forest districts from 1997 to 2020. At present, data is being filled in for the Omsk Region, Primorsky Krai of the Russian Federation and the Osh Region of the Kyrgyz Republic.
The Mukhrino field station has participated in the national project on the inventory of carbon fluxes and pools in the terrestrial ecosystems of Russia since 2022. The development of a network of ...measurements of CO2 fluxes and phytomass covered six types of bog ecosystems typical to Western Siberia. The gross ecosystem exchange (GEE) of the field-layer vegetation (medians for the period from the end of May to the end of July, mgC m−2 h−1; see errors in Results section) decreased in series: Sphagnum bog with sparse low pine trees (“Open bog”), ridges in ridge-hollow patterned bogs (“Ridge”), pine-dwarf shrub-Sphagnum bog (“Tall ryam”), hollows in patterned bogs (“S.hollow”, “E.hollow”) and pine-dwarf shrub-Sphagnum bog (“Ryam”): −220, −200, −125, −120, −109 and −86, respectively. Ecosystem respiration (Reco) here was 106, 106, 182, 55, 97 and 136. The aboveground and belowground phytomass of mosses in this series varied between 368 ± 106–472 ± 184 and 2484 ± 517–6041 ± 2079 g/m2, respectively: the aboveground phytomass of vascular plants and plant litter—15 ± 7–128 ± 95 and 10 ± 6–128 ± 43, respectively. According to the results of mathematical modeling, the best proxy for GEE, in addition to photosynthetically active radiation and soil surface temperature, was the aboveground phytomass of vascular plants (PhV), and for Reco—PhV and the mass of the plant litter of vascular plants.
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