We consider the problem of distributing the stress-strain state (SSS) characteristics in the body arbitrarily loaded on the outer surface and weakened by a physical cut with a thickness of δ0. It is assumed that δ0 ...We consider the problem of distributing the stress-strain state (SSS) characteristics in the body arbitrarily loaded on the outer surface and weakened by a physical cut with a thickness of δ0. It is assumed that δ0 parameter is the smallest possible size permitting the use of the hypothesis of continuity. The continuation of the physical cut divides the body into two parts interacting with one another by means of a contact with δ-layer. Due to constant average stresses and strains over the layer thickness, the problem reduces to the system of variational equations for the displacement fields in the adjacent bodies. The geometry of the bodies under consideration has no singular points and, as a consequence, has no singularity of stresses. The use of average characteristics makes it possible to disregard a form of the physical cut end. The obtained solution can be used for processing of experimental data in order to establish the continuity scale δ0. The entered structure parameter for silicate glass is assessed using known mechanical characteristics.展开更多
A physical cut model is used to describe the changes in the stress-strain state （SSS） in elastoplastic bodies weakened by cracks. The distance between the crack edges is considered to be finite in contrast to the ma...A physical cut model is used to describe the changes in the stress-strain state （SSS） in elastoplastic bodies weakened by cracks. The distance between the crack edges is considered to be finite in contrast to the mathematical cut. The interactive layer with a thickness limited by the possibility of using the hypothesis of continuity is distinguished on the physical cut extension, Distribution of stresses and strains over the layer thickness is constant and does not depend on the geometry of the boundary between the cut and the interactive layer. The relationship between stresses and strains is determined by the deformation plasticity theory. The problem of plane strain or plane stress state of an arbitrary finite body weakened by a physical cut is reduced to solving a system of two variational equations for displacement fields in the body parts adjacent to the interactive layer. The proposed approach eliminates the singularity in stress distribution in contrast to the mathematical cut model. Use of local strength criteria allows us to determine the time, point and direction of the fracture initiation. Possibilities of the proposed model are illustrated by solving the problems of determining the SSS of a rectangular body weakened by a physical cut under symmetric and antisymmetric loadings.展开更多
One of the promising methods for rock cutting technology is the use of high-speed water jets.In order to improve the cutting capacity of water jets without increasing the hydraulic power of equipment,pulsed water jets...One of the promising methods for rock cutting technology is the use of high-speed water jets.In order to improve the cutting capacity of water jets without increasing the hydraulic power of equipment,pulsed water jets are basically used to increase the rock cutting efficiency.However,there are no mature recommendations for selection of rational parameters,and the relationship between indicators of rock cutting efficiency and parameters of pulsed water jet is still not established.In this context,we aimed at developing a generalized equation for calculating rock cutting efficiency,in which all the major parameters in consideration of rock cutting process are included.Then,a calibration of the rational parameters of rock cutting by pulsed water jets was conducted.The results are likely helpful for increasing productivity and reducing energy consumption.展开更多
Precipitate hardening is the most easiest and effective way to enhance strain recovery properties in NiTiHf high-temperature shape memory alloys.This paper discusses the precipitation,coarsening and age hardening of H...Precipitate hardening is the most easiest and effective way to enhance strain recovery properties in NiTiHf high-temperature shape memory alloys.This paper discusses the precipitation,coarsening and age hardening of H-phase precipitates in Ni_(50)Ti_(30)Hf_(20)alloy during isothermal aging at temperatures between 450℃and 650℃for time to 75 h.The H-phase mean size and volume fraction were determined using transmission electron microscopy.Precipitation kinetics was analyzed using the Johnson-Mehl-Avrami-Kolmogorov equation and an Arrhenius type law.From these analyses,a Time-Temperature-Transformation diagram was constructed.The evolution of H-phase size suggests classical matrix diffusion limited Lifshitz-Slyozov-Wagner coarsening for all considered temperatures.The coarsening rate constants of H-phase precipitation have been determined using a modified coarsening rate equation for nondilute solutions.Critical size of H-phase precipitates for breaking down the precipitate/matrix interface coherency was estimated through a combination of age hardening and precipitate size evolution data.Moreover,time-temperature-hardness diagram was constructed from the precipitation and coarsening kinetics and age hardening of H-phase precipitates in Ni_(50)Ti_(30)Hf_(20)alloy.展开更多
The simultaneous influence of thermal and mechanical treatment was applied to produce a geometrically complex shaft from 51CrV4 steel leading to the formation of mierostruetures which were significantly different from...The simultaneous influence of thermal and mechanical treatment was applied to produce a geometrically complex shaft from 51CrV4 steel leading to the formation of mierostruetures which were significantly different from each other. These mierostrue- rural differences were accompanied by a local change of mechanical properties in terms of hardness, electrical resistivity and especially internal friction. The Snoek-KSster peak was recognized and analyzed in the structure of this steel.展开更多
We study Jackson＇s inequality between the best approximation of a function f∈ L2（R^3） by entire functions of exponential spherical type and its generalized modulus of continuity. We prove Jackson＇s inequality wit...We study Jackson＇s inequality between the best approximation of a function f∈ L2（R^3） by entire functions of exponential spherical type and its generalized modulus of continuity. We prove Jackson＇s inequality with the exact constant and the optimal argument in the modulus of continuity. In particular, Jackson＇s inequality with the optimal parameters is obtained for classical modulus of continuity of order r and Thue-Morse modulus of continuity of order r∈ N. These results are based on the solution of the generalized Logan problem for entire functions of exponential type. For it we construct a new quadrature formulas for entire functions of exponential type.展开更多
Worldwide wastewater treatment plants generate enormous amounts of sewage sludge,and their further disposal depends on the treatment technologies applied and spontaneously occurring microbiological processes.From diff...Worldwide wastewater treatment plants generate enormous amounts of sewage sludge,and their further disposal depends on the treatment technologies applied and spontaneously occurring microbiological processes.From different ages urban sewage sludge,12 strains of bacteria with simultaneous tolerance to two or more trace elements:Co,Ni,Cu,Zn,Cd and Pb at concentration of 3-5 mmol were isolated and identified by PCR of target genes and Sanger sequencing methods.The isloated metal(loids)tolerant strains belong to the species,i.e.,Serratia fonticola,Rhodococcus qingshengii,Pseudomonas fragi,Pseudomonas extremaustralis,Pseudomonas cedrina,Stenotrophomonas maltophilia,Serratia liquefaciens and Citrobacter freundii.The ecological features of the isolated strains were studied.The optimal growth temperatures for most strains was 15-30°C at pH range of 5-9,although some strains grew at 7°C(Pseudomonas fragi SS0-4,Serratia fonticola SS0-9 and Serratia fonticola SS12-11).Satisfactory growth of two strains(Serratia fonticola SS0-1and Citrobacter freundii SS60-12)was noted in an acidic medium at pH 4.Most of the strains grew in the NaCl concentration range of 1-5%.The isolated bacteria resistant to high concentrations of trace elements can be used for the effective mineralization of sewage sludge and for the decontamination of wastewater.展开更多
文摘We consider the problem of distributing the stress-strain state (SSS) characteristics in the body arbitrarily loaded on the outer surface and weakened by a physical cut with a thickness of δ0. It is assumed that δ0 parameter is the smallest possible size permitting the use of the hypothesis of continuity. The continuation of the physical cut divides the body into two parts interacting with one another by means of a contact with δ-layer. Due to constant average stresses and strains over the layer thickness, the problem reduces to the system of variational equations for the displacement fields in the adjacent bodies. The geometry of the bodies under consideration has no singular points and, as a consequence, has no singularity of stresses. The use of average characteristics makes it possible to disregard a form of the physical cut end. The obtained solution can be used for processing of experimental data in order to establish the continuity scale δ0. The entered structure parameter for silicate glass is assessed using known mechanical characteristics.
基金supported by the Russian Ministry of Education and Science(government task No.467)the Russian Foundation for Basic Research(Grant Nos.13-08-00134 and 13-01-97501)
文摘A physical cut model is used to describe the changes in the stress-strain state （SSS） in elastoplastic bodies weakened by cracks. The distance between the crack edges is considered to be finite in contrast to the mathematical cut. The interactive layer with a thickness limited by the possibility of using the hypothesis of continuity is distinguished on the physical cut extension, Distribution of stresses and strains over the layer thickness is constant and does not depend on the geometry of the boundary between the cut and the interactive layer. The relationship between stresses and strains is determined by the deformation plasticity theory. The problem of plane strain or plane stress state of an arbitrary finite body weakened by a physical cut is reduced to solving a system of two variational equations for displacement fields in the body parts adjacent to the interactive layer. The proposed approach eliminates the singularity in stress distribution in contrast to the mathematical cut model. Use of local strength criteria allows us to determine the time, point and direction of the fracture initiation. Possibilities of the proposed model are illustrated by solving the problems of determining the SSS of a rectangular body weakened by a physical cut under symmetric and antisymmetric loadings.
文摘One of the promising methods for rock cutting technology is the use of high-speed water jets.In order to improve the cutting capacity of water jets without increasing the hydraulic power of equipment,pulsed water jets are basically used to increase the rock cutting efficiency.However,there are no mature recommendations for selection of rational parameters,and the relationship between indicators of rock cutting efficiency and parameters of pulsed water jet is still not established.In this context,we aimed at developing a generalized equation for calculating rock cutting efficiency,in which all the major parameters in consideration of rock cutting process are included.Then,a calibration of the rational parameters of rock cutting by pulsed water jets was conducted.The results are likely helpful for increasing productivity and reducing energy consumption.
基金supported by the National Natural Sci-ence Foundation of China(Nos.52050410340 and 51971072)the Fundamental Research Funds for the Central University(No.3072021CFJ1002).
文摘Precipitate hardening is the most easiest and effective way to enhance strain recovery properties in NiTiHf high-temperature shape memory alloys.This paper discusses the precipitation,coarsening and age hardening of H-phase precipitates in Ni_(50)Ti_(30)Hf_(20)alloy during isothermal aging at temperatures between 450℃and 650℃for time to 75 h.The H-phase mean size and volume fraction were determined using transmission electron microscopy.Precipitation kinetics was analyzed using the Johnson-Mehl-Avrami-Kolmogorov equation and an Arrhenius type law.From these analyses,a Time-Temperature-Transformation diagram was constructed.The evolution of H-phase size suggests classical matrix diffusion limited Lifshitz-Slyozov-Wagner coarsening for all considered temperatures.The coarsening rate constants of H-phase precipitation have been determined using a modified coarsening rate equation for nondilute solutions.Critical size of H-phase precipitates for breaking down the precipitate/matrix interface coherency was estimated through a combination of age hardening and precipitate size evolution data.Moreover,time-temperature-hardness diagram was constructed from the precipitation and coarsening kinetics and age hardening of H-phase precipitates in Ni_(50)Ti_(30)Hf_(20)alloy.
文摘The simultaneous influence of thermal and mechanical treatment was applied to produce a geometrically complex shaft from 51CrV4 steel leading to the formation of mierostruetures which were significantly different from each other. These mierostrue- rural differences were accompanied by a local change of mechanical properties in terms of hardness, electrical resistivity and especially internal friction. The Snoek-KSster peak was recognized and analyzed in the structure of this steel.
基金Supported by the Russian Foundation for Basic Research(Grant No.16-01-00308)
文摘We study Jackson＇s inequality between the best approximation of a function f∈ L2（R^3） by entire functions of exponential spherical type and its generalized modulus of continuity. We prove Jackson＇s inequality with the exact constant and the optimal argument in the modulus of continuity. In particular, Jackson＇s inequality with the optimal parameters is obtained for classical modulus of continuity of order r and Thue-Morse modulus of continuity of order r∈ N. These results are based on the solution of the generalized Logan problem for entire functions of exponential type. For it we construct a new quadrature formulas for entire functions of exponential type.
基金funded by the Russian Science Foundation Grant No.22-24-20074(regional competition),held jointly with the authorities of the subject of the Russian Federation:Tula region.
文摘Worldwide wastewater treatment plants generate enormous amounts of sewage sludge,and their further disposal depends on the treatment technologies applied and spontaneously occurring microbiological processes.From different ages urban sewage sludge,12 strains of bacteria with simultaneous tolerance to two or more trace elements:Co,Ni,Cu,Zn,Cd and Pb at concentration of 3-5 mmol were isolated and identified by PCR of target genes and Sanger sequencing methods.The isloated metal(loids)tolerant strains belong to the species,i.e.,Serratia fonticola,Rhodococcus qingshengii,Pseudomonas fragi,Pseudomonas extremaustralis,Pseudomonas cedrina,Stenotrophomonas maltophilia,Serratia liquefaciens and Citrobacter freundii.The ecological features of the isolated strains were studied.The optimal growth temperatures for most strains was 15-30°C at pH range of 5-9,although some strains grew at 7°C(Pseudomonas fragi SS0-4,Serratia fonticola SS0-9 and Serratia fonticola SS12-11).Satisfactory growth of two strains(Serratia fonticola SS0-1and Citrobacter freundii SS60-12)was noted in an acidic medium at pH 4.Most of the strains grew in the NaCl concentration range of 1-5%.The isolated bacteria resistant to high concentrations of trace elements can be used for the effective mineralization of sewage sludge and for the decontamination of wastewater.
