A series of plane-strain physical model experiments are carried out to study the spatiotemporal evolution rule of rocks fracture surrounding gob-side roadway, which is subjected to the pressure induced by the mining p...A series of plane-strain physical model experiments are carried out to study the spatiotemporal evolution rule of rocks fracture surrounding gob-side roadway, which is subjected to the pressure induced by the mining process. The digital photogrammetry technology and large deformation analysis method are applied to measure the deformation and fracture of surrounding rocks. The experimental results indicate that the deformation and fracture of coal pillars are the cause to the instability and failure of the surrounding rocks. The spatiotemporal evolution rule of the rock deformation and fracture surrounding gob-side roadway is obtained. The coal pillar and the roof near coal pillar should be strengthened in support design. The engineering application results also can provide a useful guide that the combined support with wire meshes, beam, anchor bolt and cable is an effective method.展开更多
In this paper, an improved hybrid differential evolution-estimation of distribution algorithm (IHDE-EDA) is proposed for nonlinear programming (NLP) and mixed integer nonlinear programming (MINLP) models in engineerin...In this paper, an improved hybrid differential evolution-estimation of distribution algorithm (IHDE-EDA) is proposed for nonlinear programming (NLP) and mixed integer nonlinear programming (MINLP) models in engineering optimization fields. In order to improve the global searching ability and convergence speed, IHDE-EDA takes full advantage of differential information and global statistical information extracted respectively from differential evolution algorithm and annealing mechanism-embedded estimation of distribution algorithm. Moreover, the feasibility rules are used to handle constraints, which do not require additional parameters and can guide the population to the feasible region quickly. The effectiveness of hybridization mechanism of IHDE-EDA is first discussed, and then simulation and comparison based on three benchmark problems demonstrate the efficiency, accuracy and robustness of IHDE-EDA. Finally, optimization on an industrial-size scheduling of two-pipeline crude oil blending problem shows the practical applicability of IHDE-EDA.展开更多
High strength β titanium alloys are widely used in large load bearing components in the aerospace field. At present, large parts are generally formed by die forging. Different initial microstructures and deformation ...High strength β titanium alloys are widely used in large load bearing components in the aerospace field. At present, large parts are generally formed by die forging. Different initial microstructures and deformation process parameters will significantly affect the flow behavior. To precisely control the microstructures, researchers have conducted many studies to analyze the microstructure evolution law and deformation mechanism during hot compression. This review focuses on the microstructure evolution of high strength β titanium alloys during hot deformation, including dynamic recrystallization and dynamic recovery in the single-phase region and the dynamic evolution of the α phase in the two-phase region. Furthermore, the optimal hot processing regions, instability regions,and the relationship between the efficiency of power dissipation and the deformation mechanism in the hot processing map are summarized. Finally, the problems and development direction of using hot processing maps to optimize process parameters are also emphasized.展开更多
Aiming at the circular chamber under uniform stress field in deep energy storage and mining,analytical solutions of stress and plastic zone of the surrounding rock under different far-field stress and internal pressur...Aiming at the circular chamber under uniform stress field in deep energy storage and mining,analytical solutions of stress and plastic zone of the surrounding rock under different far-field stress and internal pressure were derived based on bi-modulus theory and the elastic-brittle-ideal plastic constitutive model.Evolution trend of the elasticplastic stress and plastic region with different elastic constant ratios and residual strength coefficients were analyzed in details.Results revealed that when the internal pressure was small,the three-direction principal stress was compressive stress and the stress field distribution of the surrounding rock was not affected by the moduli difference.The obtained solution was consistent with the solution from the elastic-brittle plastic drop model under the equal modulus theory.On the other hand,when the internal pressure was large,the tangential stress was changed.The surrounding rock can be divided into three zones,i.e.,tensile plastic zone(TPZ),tensile elastic zone(TEZ)and compressive elastic zone(CEZ).The tensile and compressive dual modulus had significant influence on the demarcation point between TEZ and CEZ.In addition,the strength drop and the dual modulus characteristic had a coupling effect on the stress distribution in the surrounding rock.The related achievements further enrich the theory of deep rock mechanics.展开更多
In the light of the localized progressive damage model,the evolution law of cohesive and frictional strength with irreversible strains was determined.Then,the location and the extent of the excavation disturbed zone i...In the light of the localized progressive damage model,the evolution law of cohesive and frictional strength with irreversible strains was determined.Then,the location and the extent of the excavation disturbed zone in one deep rock engineering were predicted by using the strength evolution law.The theoretical result is close to the result of in-situ test.The strength evolution law excels the elastic-perfectly plastic model and elasto-brittle plastic model in which the cohesive and frictional strength are mobilized simultaneously.The results obtained indicate that the essential failure mechanism of the cracked rock can be described by the cohesion weakening and friction strengthening evolution law.展开更多
As one of the eight Taihang passes,Fukou Xing is located in the south of the Taihang Mountains and has been an important passage for Shanxi and Hebei in history.Taking traditional settlements in Fukou Xing Region as r...As one of the eight Taihang passes,Fukou Xing is located in the south of the Taihang Mountains and has been an important passage for Shanxi and Hebei in history.Taking traditional settlements in Fukou Xing Region as research object,using the Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER) Global Digital Elevation Model(GDEM)(remote sensing measurement of elevation data) and GIS platform,this paper made a quantitative study on traditional settlement space in mountain environment of this region,and studied space parameters including elevation,terrain,aspect,and boundary,observed and summarized the spatial features.In addition,based on the local chronicles of Ming and Qing dynasties,it mutually verified the quantitative conclusions and qualitative cognition,analyzed the evolution rules of traditional settlements in Fukou Xing region,and finally obtained new understandings of spatial features of traditional settlements in Fukou Xing region.展开更多
In the present study,in order to investigate the effects of fly ash on the structural evolution and strength damage mechanism of Pisha-sandstone cement soil,unconfined compressive strength tests of Pisha-sandstone cem...In the present study,in order to investigate the effects of fly ash on the structural evolution and strength damage mechanism of Pisha-sandstone cement soil,unconfined compressive strength tests of Pisha-sandstone cement soil with different fly ash content levels and various ages were carried out.The apparent morphology,microstructures,and chemical compositions of the samples were observed and analyzed using ultra-depth three-dimensional microscopy,scanning electron microscopy,and XRD methods.The results revealed that the unconfined compressive strength levels of Pisha-sandstone cement soil samples displayed increasing trends with the increases in fly ash content and age.For example,when the fly ash content levels were increased from 12%to 15%,the strength of Pisha-sandstone cement soil had only slightly increased under the curing ages of 7,28,and 60 days.In addition,the unconfined compressive strength levels of the samples with 15%fly ash content only increased 0.02%,0.51%,and 0.54%,respectively,when compared with the samples containing 12%fly ash.It was observed that with the increases in the fly ash content,the number of pores on the outer surfaces of the samples were significantly reduced.Also,the height differences of cross-sectional gullies were reduced,and the apparent morphology was observed to be flatter.Since cement hydration creates a strong alkaline environment for reaction systems,the active degrees of the pozzolanic reactions of the fly ash were stimulated in this study.Moreover,a significant amount of the C-S-H gel phase and the stable five-membered ring structure of the mordenite and ettringite were generated,which connected the loose Pisha-sandstone particles to form a skeleton.The internal microstructures were then observed to be denser and more uniform.At the same time,the micro-pores were filled and refined by the unreacted micro-bead fly ash.Consequently,the defects in the internal microstructures were improved.Also,based on the Weibull distribution,a damage evolution model of the Pisha-sandstone cement soil was established.The analysis results of the damage variable D values during the initial damage stage,damage evolution stage,and residual damage stage of the damage process showed that the damage variables during all three stages displayed decreasing trends with the increases in the fly ash content levels and age.Therefore,based on this study’s findings,it was considered that the incorporation of fly ash could effectively improve the damage degrees of Pisha-sandstone cement soil under external force conditions.展开更多
Effects of the debinding atmosphere,powder characteristic,solid loading and heating rate on the compact deformation were investigated.The compact strength after thermal debinding was measured by bending mode.The exper...Effects of the debinding atmosphere,powder characteristic,solid loading and heating rate on the compact deformation were investigated.The compact strength after thermal debinding was measured by bending mode.The experimental results indicate that the vacuum atmosphere is beneficial to improving the deformation resistance compared with nitrogen atmosphere.Small particle size,irregular particle shape and high solid loading are suitable for decreasing the deformation defects.Besides,too fast heating rate may induce deformation defects.It is also indicated that effect of the factors for the deformation defects is different in different debinding stages.The strength evolution of the compacts during thermal debinding was also discussed.展开更多
We discussed the decrease in residual stress,precipitation evolution,and mechanical properties of GH4151 alloy in different annealing temperatures,which were studied by the scanning electron microscope(SEM),high-resol...We discussed the decrease in residual stress,precipitation evolution,and mechanical properties of GH4151 alloy in different annealing temperatures,which were studied by the scanning electron microscope(SEM),high-resolution transmission electron microscopy(HRTEM),and electron backscatter diffraction(EBSD).The findings reveal that annealing processing has a significant impact on diminishing residual stresses.As the annealing temperature rose from 950 to 1150℃,the majority of the residual stresses were relieved from 60.1 MPa down to 10.9 MPa.Moreover,the stress relaxation mechanism transitioned from being mainly controlled by dislocation slip to a combination of dislocation slip and grain boundary migration.Meanwhile,the annealing treatment promotes the decomposition of the Laves,accompanied by the precipitation ofμ-(Mo_(6)Co_(7))starting at 950℃ and reaching a maximum value at 1050℃.The tensile strength and plasticity of the annealing alloy at 1150℃ reached the maximum(1394 MPa,56.1%)which was 131%,200%fold than those of the as-cast alloy(1060 MPa,26.6%),but the oxidation process in the alloy was accelerated at 1150℃.The enhancement in durability and flexibility is primarily due to the dissolution of the brittle phase,along with the shape and dispersal of theγ′phase.展开更多
In this paper, evolutions of ruled surfaces generated by the quasi normal and quasi binormal vector fields of space curve are presented. These evolutions of the ruled surfaces depend on the evolutions of their directr...In this paper, evolutions of ruled surfaces generated by the quasi normal and quasi binormal vector fields of space curve are presented. These evolutions of the ruled surfaces depend on the evolutions of their directrix using quasi frame along a space curve.展开更多
The authors regret that in the paper of Baldovino et al.(2019),published in Journal of Rock Mechanics and Geotechnical Engineering(JRMGE),Eq.(2)must be corrected.Eq.(2)in the original paper describes a formula to calc...The authors regret that in the paper of Baldovino et al.(2019),published in Journal of Rock Mechanics and Geotechnical Engineering(JRMGE),Eq.(2)must be corrected.Eq.(2)in the original paper describes a formula to calculate the unconfined compressive strength(q_u).But Authors wrote it as if it were the formula for calculating the split tensile strength(qt).To amend this error,Eq.(1)and Eq.(2)are the correct expressions for q_u and q_t measurements,respectively.展开更多
An information system is a type of knowledge representation,and attribute reduction is crucial in big data,machine learning,data mining,and intelligent systems.There are several ways for solving attribute reduction pr...An information system is a type of knowledge representation,and attribute reduction is crucial in big data,machine learning,data mining,and intelligent systems.There are several ways for solving attribute reduction problems,but they all require a common categorization.The selection of features in most scientific studies is a challenge for the researcher.When working with huge datasets,selecting all available attributes is not an option because it frequently complicates the study and decreases performance.On the other side,neglecting some attributes might jeopardize data accuracy.In this case,rough set theory provides a useful approach for identifying superfluous attributes that may be ignored without sacrificing any significant information;nonetheless,investigating all available combinations of attributes will result in some problems.Furthermore,because attribute reduction is primarily a mathematical issue,technical progress in reduction is dependent on the advancement of mathematical models.Because the focus of this study is on the mathematical side of attribute reduction,we propose some methods to make a reduction for information systems according to classical rough set theory,the strength of rules and similarity matrix,we applied our proposed methods to several examples and calculate the reduction for each case.These methods expand the options of attribute reductions for researchers.展开更多
A systematic method was developed for ice-class propeller modeling,performance estimation,strength and integrity evaluation and optimization.To estimate the impact of sea ice on the propeller structure,URI3 rules,esta...A systematic method was developed for ice-class propeller modeling,performance estimation,strength and integrity evaluation and optimization.To estimate the impact of sea ice on the propeller structure,URI3 rules,established by the International Association of Classification Societies in 2007,were applied for ice loading calculations.An R-class propeller(a type of ice-class propeller)was utilized for subsequent investigations.The propeller modeling was simplified based on a conventional method,which expedited the model building process.The propeller performance was simulated using the computational fluid dynamics(CFD)method.The simulation results were validated by comparison with experimental data.Furthermore,the hydrodynamic pressure was transferred into a finite element analysis(FEA)module for strength assessment of ice-class propellers.According to URI3 rules,the ice loading was estimated based on different polar classes and working cases.Then,the FEA method was utilized to evaluate the propeller strength.The validation showed that the simulation results accorded with recent research results.Finally,an improved optimization method was developed to save the propeller constituent materials.The optimized propeller example had a minimum safety factor of 1.55,satisfying the safety factor requirement of≥1.5,and reduced the design volume to 88.2%of the original.展开更多
The size effect rule of roller compacted concrete (RCC) fracture toughness was reached on the analysis of fracture toughness of RCC specimens, which have been done by project team. And then the rule was applied to the...The size effect rule of roller compacted concrete (RCC) fracture toughness was reached on the analysis of fracture toughness of RCC specimens, which have been done by project team. And then the rule was applied to the calculation formula of equivalent strength of crack director in the RCC arch dam, thus a simple and useful formula was reached. The study shows that the equivalent strength of crack directors increases with the increasing intensity of concrete, but the surplus rate of strength of crack directors section decreases with the increasing intensity of concrete and the distance between centers of adjacent crack directors, and that bilateral interval crack directors are more efficient in weakening the strength of section than unidirectional interval crack directors in the case of the same distance between adjacent crack director centers. A good design for crack directors of RCC arch dam is proposed via the rule.展开更多
The competition among modem enterprises has been converted from products to capability. As the basis of competition, production system can＇t win the market unless it takes advantage of its capability in competition. ...The competition among modem enterprises has been converted from products to capability. As the basis of competition, production system can＇t win the market unless it takes advantage of its capability in competition. Here in this article, the evolutionary rules of production system contributing to the establishment, renovation, reform, invention and promotion of the production of modem enterprises are observed.展开更多
As it developed to today, Volleyball evolved from a game for the purpose of entertainment initially to a competitive Olympic sport. Through various periods of Volleyball development, we can find that when some old rul...As it developed to today, Volleyball evolved from a game for the purpose of entertainment initially to a competitive Olympic sport. Through various periods of Volleyball development, we can find that when some old rules can not adapt to the volleyball development, it will lead to changes in the rules, it is this continuous improvement and change that inject vigor to volleyball and bring vitality, and promote the innovative development of volleyball skills and tactics, in turn the constant enrichment and development of volleyball skills and tactics required the game rules constantly revised and improved, as promoted and restricted each other, analysis of the mutual relationship between volleyball game rules and technology or tactics can not only in favor of volleyball skills, like evolving tactics, but also beneficial to volleyball competition rules maturity. Development of Volleyball Rules has been the inexhaustible power to development of sports project, researching of the competition rules has been recognized as a major breakthrough in the field of sports in various projects to promote sports development. Volleyball Rules - from the generated moment until today, has evolved many times. This evolution is not blind, random; it follows its inherent rule. A contest rule, which has a close relationship with the development of sports technology, are the basic norms and principles of sports game. They promote each other, while mutually restraint. Analysis of the relationship between volleyball competition rules and the technology or tactics, is not only conducive to the development of athletic skills, but also to the maturity of competition rules.展开更多
基金supported by the National Natural Science Foundation of China (No. 51174197)the Major State Basic Research Development Program of China (No. 2014CB046905)+1 种基金State Key Laboratory for Geo Mechanics and Deep Underground Engineering (CUMT) (No. SKLGDUEK1503)the ‘Qing Lan’ Project of Jiangsu Province
文摘A series of plane-strain physical model experiments are carried out to study the spatiotemporal evolution rule of rocks fracture surrounding gob-side roadway, which is subjected to the pressure induced by the mining process. The digital photogrammetry technology and large deformation analysis method are applied to measure the deformation and fracture of surrounding rocks. The experimental results indicate that the deformation and fracture of coal pillars are the cause to the instability and failure of the surrounding rocks. The spatiotemporal evolution rule of the rock deformation and fracture surrounding gob-side roadway is obtained. The coal pillar and the roof near coal pillar should be strengthened in support design. The engineering application results also can provide a useful guide that the combined support with wire meshes, beam, anchor bolt and cable is an effective method.
基金Supported by the National Basic Research Program of China (2012CB720500)the National Natural Science Foundation of China (60974008)
文摘In this paper, an improved hybrid differential evolution-estimation of distribution algorithm (IHDE-EDA) is proposed for nonlinear programming (NLP) and mixed integer nonlinear programming (MINLP) models in engineering optimization fields. In order to improve the global searching ability and convergence speed, IHDE-EDA takes full advantage of differential information and global statistical information extracted respectively from differential evolution algorithm and annealing mechanism-embedded estimation of distribution algorithm. Moreover, the feasibility rules are used to handle constraints, which do not require additional parameters and can guide the population to the feasible region quickly. The effectiveness of hybridization mechanism of IHDE-EDA is first discussed, and then simulation and comparison based on three benchmark problems demonstrate the efficiency, accuracy and robustness of IHDE-EDA. Finally, optimization on an industrial-size scheduling of two-pipeline crude oil blending problem shows the practical applicability of IHDE-EDA.
基金supported by the Project of National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, China (No. 6142909190207)Shaanxi Key Laboratory of High-performance Precision Forming Technology and Equipment (SKL-HPFTE), China (No. PETE-2019-KF-01)。
文摘High strength β titanium alloys are widely used in large load bearing components in the aerospace field. At present, large parts are generally formed by die forging. Different initial microstructures and deformation process parameters will significantly affect the flow behavior. To precisely control the microstructures, researchers have conducted many studies to analyze the microstructure evolution law and deformation mechanism during hot compression. This review focuses on the microstructure evolution of high strength β titanium alloys during hot deformation, including dynamic recrystallization and dynamic recovery in the single-phase region and the dynamic evolution of the α phase in the two-phase region. Furthermore, the optimal hot processing regions, instability regions,and the relationship between the efficiency of power dissipation and the deformation mechanism in the hot processing map are summarized. Finally, the problems and development direction of using hot processing maps to optimize process parameters are also emphasized.
基金Projects(51774196,52074169)supported by the National Natural Science Foundation of China。
文摘Aiming at the circular chamber under uniform stress field in deep energy storage and mining,analytical solutions of stress and plastic zone of the surrounding rock under different far-field stress and internal pressure were derived based on bi-modulus theory and the elastic-brittle-ideal plastic constitutive model.Evolution trend of the elasticplastic stress and plastic region with different elastic constant ratios and residual strength coefficients were analyzed in details.Results revealed that when the internal pressure was small,the three-direction principal stress was compressive stress and the stress field distribution of the surrounding rock was not affected by the moduli difference.The obtained solution was consistent with the solution from the elastic-brittle plastic drop model under the equal modulus theory.On the other hand,when the internal pressure was large,the tangential stress was changed.The surrounding rock can be divided into three zones,i.e.,tensile plastic zone(TPZ),tensile elastic zone(TEZ)and compressive elastic zone(CEZ).The tensile and compressive dual modulus had significant influence on the demarcation point between TEZ and CEZ.In addition,the strength drop and the dual modulus characteristic had a coupling effect on the stress distribution in the surrounding rock.The related achievements further enrich the theory of deep rock mechanics.
基金Project(50708034)supported by the National Natural Science Foundation of ChinaProject(20060400263)supported by China Postdoctoral Science FoundationProject(2007RS4031)supported by the Provincial Science and Technology Plan of Hunan,China
文摘In the light of the localized progressive damage model,the evolution law of cohesive and frictional strength with irreversible strains was determined.Then,the location and the extent of the excavation disturbed zone in one deep rock engineering were predicted by using the strength evolution law.The theoretical result is close to the result of in-situ test.The strength evolution law excels the elastic-perfectly plastic model and elasto-brittle plastic model in which the cohesive and frictional strength are mobilized simultaneously.The results obtained indicate that the essential failure mechanism of the cracked rock can be described by the cohesion weakening and friction strengthening evolution law.
基金Sponsored by Project of National Natural Science Foundation(51608007)"Young Top-notch Talent Support Plan" of North China University of Technology
文摘As one of the eight Taihang passes,Fukou Xing is located in the south of the Taihang Mountains and has been an important passage for Shanxi and Hebei in history.Taking traditional settlements in Fukou Xing Region as research object,using the Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER) Global Digital Elevation Model(GDEM)(remote sensing measurement of elevation data) and GIS platform,this paper made a quantitative study on traditional settlement space in mountain environment of this region,and studied space parameters including elevation,terrain,aspect,and boundary,observed and summarized the spatial features.In addition,based on the local chronicles of Ming and Qing dynasties,it mutually verified the quantitative conclusions and qualitative cognition,analyzed the evolution rules of traditional settlements in Fukou Xing region,and finally obtained new understandings of spatial features of traditional settlements in Fukou Xing region.
基金This study was funded by the National Natural Science Foundation of China(Grant No.51869022).
文摘In the present study,in order to investigate the effects of fly ash on the structural evolution and strength damage mechanism of Pisha-sandstone cement soil,unconfined compressive strength tests of Pisha-sandstone cement soil with different fly ash content levels and various ages were carried out.The apparent morphology,microstructures,and chemical compositions of the samples were observed and analyzed using ultra-depth three-dimensional microscopy,scanning electron microscopy,and XRD methods.The results revealed that the unconfined compressive strength levels of Pisha-sandstone cement soil samples displayed increasing trends with the increases in fly ash content and age.For example,when the fly ash content levels were increased from 12%to 15%,the strength of Pisha-sandstone cement soil had only slightly increased under the curing ages of 7,28,and 60 days.In addition,the unconfined compressive strength levels of the samples with 15%fly ash content only increased 0.02%,0.51%,and 0.54%,respectively,when compared with the samples containing 12%fly ash.It was observed that with the increases in the fly ash content,the number of pores on the outer surfaces of the samples were significantly reduced.Also,the height differences of cross-sectional gullies were reduced,and the apparent morphology was observed to be flatter.Since cement hydration creates a strong alkaline environment for reaction systems,the active degrees of the pozzolanic reactions of the fly ash were stimulated in this study.Moreover,a significant amount of the C-S-H gel phase and the stable five-membered ring structure of the mordenite and ettringite were generated,which connected the loose Pisha-sandstone particles to form a skeleton.The internal microstructures were then observed to be denser and more uniform.At the same time,the micro-pores were filled and refined by the unreacted micro-bead fly ash.Consequently,the defects in the internal microstructures were improved.Also,based on the Weibull distribution,a damage evolution model of the Pisha-sandstone cement soil was established.The analysis results of the damage variable D values during the initial damage stage,damage evolution stage,and residual damage stage of the damage process showed that the damage variables during all three stages displayed decreasing trends with the increases in the fly ash content levels and age.Therefore,based on this study’s findings,it was considered that the incorporation of fly ash could effectively improve the damage degrees of Pisha-sandstone cement soil under external force conditions.
基金Project(200135)supported by the National Excellent Dissertation Foundation of ChinaProject(NECT-04-0754)supported by the Programfor New Century Excellent Talents in University of China
文摘Effects of the debinding atmosphere,powder characteristic,solid loading and heating rate on the compact deformation were investigated.The compact strength after thermal debinding was measured by bending mode.The experimental results indicate that the vacuum atmosphere is beneficial to improving the deformation resistance compared with nitrogen atmosphere.Small particle size,irregular particle shape and high solid loading are suitable for decreasing the deformation defects.Besides,too fast heating rate may induce deformation defects.It is also indicated that effect of the factors for the deformation defects is different in different debinding stages.The strength evolution of the compacts during thermal debinding was also discussed.
基金This work was financially supported by the National Science and Technology Major Project of China(No.J2019-VI-0006-0120)the National Key R&D Program of China(No.2021YFB3700402)the National Natural Science Foundation of China(Nos.52074092 and 52274330).
文摘We discussed the decrease in residual stress,precipitation evolution,and mechanical properties of GH4151 alloy in different annealing temperatures,which were studied by the scanning electron microscope(SEM),high-resolution transmission electron microscopy(HRTEM),and electron backscatter diffraction(EBSD).The findings reveal that annealing processing has a significant impact on diminishing residual stresses.As the annealing temperature rose from 950 to 1150℃,the majority of the residual stresses were relieved from 60.1 MPa down to 10.9 MPa.Moreover,the stress relaxation mechanism transitioned from being mainly controlled by dislocation slip to a combination of dislocation slip and grain boundary migration.Meanwhile,the annealing treatment promotes the decomposition of the Laves,accompanied by the precipitation ofμ-(Mo_(6)Co_(7))starting at 950℃ and reaching a maximum value at 1050℃.The tensile strength and plasticity of the annealing alloy at 1150℃ reached the maximum(1394 MPa,56.1%)which was 131%,200%fold than those of the as-cast alloy(1060 MPa,26.6%),but the oxidation process in the alloy was accelerated at 1150℃.The enhancement in durability and flexibility is primarily due to the dissolution of the brittle phase,along with the shape and dispersal of theγ′phase.
文摘In this paper, evolutions of ruled surfaces generated by the quasi normal and quasi binormal vector fields of space curve are presented. These evolutions of the ruled surfaces depend on the evolutions of their directrix using quasi frame along a space curve.
文摘The authors regret that in the paper of Baldovino et al.(2019),published in Journal of Rock Mechanics and Geotechnical Engineering(JRMGE),Eq.(2)must be corrected.Eq.(2)in the original paper describes a formula to calculate the unconfined compressive strength(q_u).But Authors wrote it as if it were the formula for calculating the split tensile strength(qt).To amend this error,Eq.(1)and Eq.(2)are the correct expressions for q_u and q_t measurements,respectively.
文摘An information system is a type of knowledge representation,and attribute reduction is crucial in big data,machine learning,data mining,and intelligent systems.There are several ways for solving attribute reduction problems,but they all require a common categorization.The selection of features in most scientific studies is a challenge for the researcher.When working with huge datasets,selecting all available attributes is not an option because it frequently complicates the study and decreases performance.On the other side,neglecting some attributes might jeopardize data accuracy.In this case,rough set theory provides a useful approach for identifying superfluous attributes that may be ignored without sacrificing any significant information;nonetheless,investigating all available combinations of attributes will result in some problems.Furthermore,because attribute reduction is primarily a mathematical issue,technical progress in reduction is dependent on the advancement of mathematical models.Because the focus of this study is on the mathematical side of attribute reduction,we propose some methods to make a reduction for information systems according to classical rough set theory,the strength of rules and similarity matrix,we applied our proposed methods to several examples and calculate the reduction for each case.These methods expand the options of attribute reductions for researchers.
基金The author would like to thank University of Tasmania and Newcastle University for their support。
文摘A systematic method was developed for ice-class propeller modeling,performance estimation,strength and integrity evaluation and optimization.To estimate the impact of sea ice on the propeller structure,URI3 rules,established by the International Association of Classification Societies in 2007,were applied for ice loading calculations.An R-class propeller(a type of ice-class propeller)was utilized for subsequent investigations.The propeller modeling was simplified based on a conventional method,which expedited the model building process.The propeller performance was simulated using the computational fluid dynamics(CFD)method.The simulation results were validated by comparison with experimental data.Furthermore,the hydrodynamic pressure was transferred into a finite element analysis(FEA)module for strength assessment of ice-class propellers.According to URI3 rules,the ice loading was estimated based on different polar classes and working cases.Then,the FEA method was utilized to evaluate the propeller strength.The validation showed that the simulation results accorded with recent research results.Finally,an improved optimization method was developed to save the propeller constituent materials.The optimized propeller example had a minimum safety factor of 1.55,satisfying the safety factor requirement of≥1.5,and reduced the design volume to 88.2%of the original.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50179002,50709013)Liaoning Province Dr. Fund(Grant No.20071025)
文摘The size effect rule of roller compacted concrete (RCC) fracture toughness was reached on the analysis of fracture toughness of RCC specimens, which have been done by project team. And then the rule was applied to the calculation formula of equivalent strength of crack director in the RCC arch dam, thus a simple and useful formula was reached. The study shows that the equivalent strength of crack directors increases with the increasing intensity of concrete, but the surplus rate of strength of crack directors section decreases with the increasing intensity of concrete and the distance between centers of adjacent crack directors, and that bilateral interval crack directors are more efficient in weakening the strength of section than unidirectional interval crack directors in the case of the same distance between adjacent crack director centers. A good design for crack directors of RCC arch dam is proposed via the rule.
文摘The competition among modem enterprises has been converted from products to capability. As the basis of competition, production system can＇t win the market unless it takes advantage of its capability in competition. Here in this article, the evolutionary rules of production system contributing to the establishment, renovation, reform, invention and promotion of the production of modem enterprises are observed.
文摘As it developed to today, Volleyball evolved from a game for the purpose of entertainment initially to a competitive Olympic sport. Through various periods of Volleyball development, we can find that when some old rules can not adapt to the volleyball development, it will lead to changes in the rules, it is this continuous improvement and change that inject vigor to volleyball and bring vitality, and promote the innovative development of volleyball skills and tactics, in turn the constant enrichment and development of volleyball skills and tactics required the game rules constantly revised and improved, as promoted and restricted each other, analysis of the mutual relationship between volleyball game rules and technology or tactics can not only in favor of volleyball skills, like evolving tactics, but also beneficial to volleyball competition rules maturity. Development of Volleyball Rules has been the inexhaustible power to development of sports project, researching of the competition rules has been recognized as a major breakthrough in the field of sports in various projects to promote sports development. Volleyball Rules - from the generated moment until today, has evolved many times. This evolution is not blind, random; it follows its inherent rule. A contest rule, which has a close relationship with the development of sports technology, are the basic norms and principles of sports game. They promote each other, while mutually restraint. Analysis of the relationship between volleyball competition rules and the technology or tactics, is not only conducive to the development of athletic skills, but also to the maturity of competition rules.
