With respect to constitutive models for continuum modeling applications, the post-yield domain remainsthe area of greatest uncertainty. Recent studies based on laboratory testing have led to thedevelopment of a number...With respect to constitutive models for continuum modeling applications, the post-yield domain remainsthe area of greatest uncertainty. Recent studies based on laboratory testing have led to thedevelopment of a number of models for brittle rock dilation, which account for both the plastic shearstrain and confining stress dependencies of this phenomenon. Although these models are useful inproviding an improved understanding of how dilatancy evolves during a compression test, there hasbeen relatively little work performed examining their validity for modeling brittle rock yield in situ. Inthis study, different constitutive models for rock dilation are reviewed and then tested, in the context of anumber of case studies, using a continuum finite-difference approach (FLAC). The uncertainty associatedwith the modeling of brittle fracture localization is addressed, and the overall ability of mobilizeddilation models to replicate in situ deformation measurements and yield patterns is evaluated. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.展开更多
This study aims to numerically and experimentally investigate the response of a medium strength rock material under unconfined compression loading up to failure. The unconfined compressive strength(UCS) is one of the ...This study aims to numerically and experimentally investigate the response of a medium strength rock material under unconfined compression loading up to failure. The unconfined compressive strength(UCS) is one of the most important parameters in characterising rock material behaviour. Hence the UCS is crucial in understanding the failure mechanism of fractured rocks. An effective approach to determine the UCS and to investigate the behaviours of rock materials under unconfined compression is essential in the majority of research fields of rock mechanics. The experimental configuration for the unconfined compression test, suggested by the protocols of the ASTM standard, has some limitations which affect the accuracy in determination of the real UCS. Among several alternative configurations proposed, the Mogi’s configuration seems to be the most appropriate one. Therefore, the ASTM and Mogi’s configurations were used to perform the tests on a medium strength rock material, i.e. Pietra Serena sandstone. The results using two configurations were discussed in terms of the differences. The tests were also replicated in LSDYNA using a finite element method(FEM) coupled smooth particle hydrodynamics(SPH) technique.This technique is employed in this study due to its capabilities to cope with large deformation issues related to the rocks. An advanced material model, called the Karagozian and Case Concrete(KCC) model,is implemented in the numerical simulations. The KCC model consists of three independent fixed failure surfaces and it can consider the damage accumulation based on the current state of stress among these failure surfaces. An equation-of-state(EOS) is used in conjunction with KCC material model for decoupling the volumetric and deviatoric responses. The numerical and experimental results were finally compared with the focus on the stress-strain diagram and the failure patterns. The comparison shows that the numerical results are in good agreement with the experimental results.展开更多
This research aims to construct a case resource library for programming course,which can be used for either teachers’teaching or students’learning.The cases cannot be simply piled up but rather require a systematic ...This research aims to construct a case resource library for programming course,which can be used for either teachers’teaching or students’learning.The cases cannot be simply piled up but rather require a systematic planning.The solution to this is to design a case system model.The outcome-based education(OBE)concept is adopted to guide the research,and a three-dimensional case system model matching the course objectives is designed.Under the guidance of the model,the case resource library construction is more planned.Cases based on the model can provide all-round support for the cultivation of students’ability by gradually promoting knowledge and technology,frequently exercising one’s abilities,as well as expanding diverse and innovative problems.展开更多
Laboratory cased-hole acoustic logging simulations are developed with the linear phased-array transmitter in scaled cased well models for evaluating the feasibility of extracting formation acoustic parameters through ...Laboratory cased-hole acoustic logging simulations are developed with the linear phased-array transmitter in scaled cased well models for evaluating the feasibility of extracting formation acoustic parameters through casing.The full waveforms are measured with different cement bonding models.By analyzing the measured wavetrains and the time-slowness correlation graphs,it is showed that when the generation conditions of the refracted compressional wave and the refracted shear wave are reached successively by regulating the direction of acoustic beam radiated from the linear phased-array transmitter,steered angle of the main radiation lobe with both good bonding interfaces.The refracted compressional wave and the refracted shear wave can be stimulated obviously and the casing wave can be suppressed effectively,even when the casing and cement(or the cement and formation) is not bonded.Based on these observations, it is worthwhile to apply the linear phased-array transmitter to determine formation velocities,particularly in poorly bonded cased well.The works establish the experimental and theoretical foundation for new generation cased-hole acoustic logging tool development.展开更多
We introduced the two-parameter stratiform cloud model of Hu and Yan (1986) into the mesoscale model ofAnthes et al. (1987), and reprogramed the latter, then constructed a three-dimensional stratiform cloud system mod...We introduced the two-parameter stratiform cloud model of Hu and Yan (1986) into the mesoscale model ofAnthes et al. (1987), and reprogramed the latter, then constructed a three-dimensional stratiform cloud system modelwhich includes three phases of water and detailed cloud physical processes. For the stability and accuracy of calculationin a larger time step, we accepted a set of hybrid-schemes for all and the time split scheme for some of the cloud physicalprocesses, and proposed a parameterized method which calculates different types of phase change processessimultaneously, and designed the falling schemes of particles following the Lagrangian method.We used a dry model, a cumulus parameterization model, a two-phase explicit scheme model, and the model pres-ented here to simulate two low-level mesoscale vortices, compared and analysed the simulating capability of these mod-els. The results show that in simulation of the circulation structure of meso-vortex, the structure of cloud system, andsurface precipitation, the model presented here is more reasonable and closer to the observations than other models.展开更多
Story understanding is one of the important branches of natural language under-standing research in AI techniques. A new approach to story understanding is proposedin this paper. The so-called Story Parsing Grammar (S...Story understanding is one of the important branches of natural language under-standing research in AI techniques. A new approach to story understanding is proposedin this paper. The so-called Story Parsing Grammar (SPG) is used to represent thestory abstracting processes with different degrees in story understanding, and the storyunderstanding process is converted to the story recognizing process done by the syn-tactic parser of SPG. This kind of story understanding is called story parsing. In thispaper, firstly, a survey of story understanding research is given. Secondly, by the clas-sification of various kinds of story structures, the so-called Case Frame Forest (CFF) isproposed to represent the superficial meaning of story. Based on CFF, a high- dimen-sional grammar, called Forest Grammar (FG), is defined. Furthermore, SPG is definedas a subclass of context-sensitive FG. Considering the context-sensitivity of story con-tent, a type of context-sensitive derivation is defined in the definition of SPG. Lastly,data about runtime efficiency of the syntactic parsing algorithm of weak precedenceSPG, a subclass of SPG, are given and analysed.展开更多
基金funding support from the Natural Sciences and Engineering Research Council of Canada (NSERC)the Center for Excellence in Mining Innovation (CEMI)the Nuclear Waste Management Organization of Canada (NWMO)
文摘With respect to constitutive models for continuum modeling applications, the post-yield domain remainsthe area of greatest uncertainty. Recent studies based on laboratory testing have led to thedevelopment of a number of models for brittle rock dilation, which account for both the plastic shearstrain and confining stress dependencies of this phenomenon. Although these models are useful inproviding an improved understanding of how dilatancy evolves during a compression test, there hasbeen relatively little work performed examining their validity for modeling brittle rock yield in situ. Inthis study, different constitutive models for rock dilation are reviewed and then tested, in the context of anumber of case studies, using a continuum finite-difference approach (FLAC). The uncertainty associatedwith the modeling of brittle fracture localization is addressed, and the overall ability of mobilizeddilation models to replicate in situ deformation measurements and yield patterns is evaluated. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.
文摘This study aims to numerically and experimentally investigate the response of a medium strength rock material under unconfined compression loading up to failure. The unconfined compressive strength(UCS) is one of the most important parameters in characterising rock material behaviour. Hence the UCS is crucial in understanding the failure mechanism of fractured rocks. An effective approach to determine the UCS and to investigate the behaviours of rock materials under unconfined compression is essential in the majority of research fields of rock mechanics. The experimental configuration for the unconfined compression test, suggested by the protocols of the ASTM standard, has some limitations which affect the accuracy in determination of the real UCS. Among several alternative configurations proposed, the Mogi’s configuration seems to be the most appropriate one. Therefore, the ASTM and Mogi’s configurations were used to perform the tests on a medium strength rock material, i.e. Pietra Serena sandstone. The results using two configurations were discussed in terms of the differences. The tests were also replicated in LSDYNA using a finite element method(FEM) coupled smooth particle hydrodynamics(SPH) technique.This technique is employed in this study due to its capabilities to cope with large deformation issues related to the rocks. An advanced material model, called the Karagozian and Case Concrete(KCC) model,is implemented in the numerical simulations. The KCC model consists of three independent fixed failure surfaces and it can consider the damage accumulation based on the current state of stress among these failure surfaces. An equation-of-state(EOS) is used in conjunction with KCC material model for decoupling the volumetric and deviatoric responses. The numerical and experimental results were finally compared with the focus on the stress-strain diagram and the failure patterns. The comparison shows that the numerical results are in good agreement with the experimental results.
基金The“OBE-Oriented Programming Course Practice Teaching Research and Resource Construction”Project supported by the Association of Fundamental Computing Education in Chinese Universities in 2021.(Project Number:2021-AFCEC-246)。
文摘This research aims to construct a case resource library for programming course,which can be used for either teachers’teaching or students’learning.The cases cannot be simply piled up but rather require a systematic planning.The solution to this is to design a case system model.The outcome-based education(OBE)concept is adopted to guide the research,and a three-dimensional case system model matching the course objectives is designed.Under the guidance of the model,the case resource library construction is more planned.Cases based on the model can provide all-round support for the cultivation of students’ability by gradually promoting knowledge and technology,frequently exercising one’s abilities,as well as expanding diverse and innovative problems.
基金supported by the National Natural Science Foundation of China(40804020)Natural Science Foundation of Shandong(ZR2011DQ020)
文摘Laboratory cased-hole acoustic logging simulations are developed with the linear phased-array transmitter in scaled cased well models for evaluating the feasibility of extracting formation acoustic parameters through casing.The full waveforms are measured with different cement bonding models.By analyzing the measured wavetrains and the time-slowness correlation graphs,it is showed that when the generation conditions of the refracted compressional wave and the refracted shear wave are reached successively by regulating the direction of acoustic beam radiated from the linear phased-array transmitter,steered angle of the main radiation lobe with both good bonding interfaces.The refracted compressional wave and the refracted shear wave can be stimulated obviously and the casing wave can be suppressed effectively,even when the casing and cement(or the cement and formation) is not bonded.Based on these observations, it is worthwhile to apply the linear phased-array transmitter to determine formation velocities,particularly in poorly bonded cased well.The works establish the experimental and theoretical foundation for new generation cased-hole acoustic logging tool development.
文摘We introduced the two-parameter stratiform cloud model of Hu and Yan (1986) into the mesoscale model ofAnthes et al. (1987), and reprogramed the latter, then constructed a three-dimensional stratiform cloud system modelwhich includes three phases of water and detailed cloud physical processes. For the stability and accuracy of calculationin a larger time step, we accepted a set of hybrid-schemes for all and the time split scheme for some of the cloud physicalprocesses, and proposed a parameterized method which calculates different types of phase change processessimultaneously, and designed the falling schemes of particles following the Lagrangian method.We used a dry model, a cumulus parameterization model, a two-phase explicit scheme model, and the model pres-ented here to simulate two low-level mesoscale vortices, compared and analysed the simulating capability of these mod-els. The results show that in simulation of the circulation structure of meso-vortex, the structure of cloud system, andsurface precipitation, the model presented here is more reasonable and closer to the observations than other models.
文摘Story understanding is one of the important branches of natural language under-standing research in AI techniques. A new approach to story understanding is proposedin this paper. The so-called Story Parsing Grammar (SPG) is used to represent thestory abstracting processes with different degrees in story understanding, and the storyunderstanding process is converted to the story recognizing process done by the syn-tactic parser of SPG. This kind of story understanding is called story parsing. In thispaper, firstly, a survey of story understanding research is given. Secondly, by the clas-sification of various kinds of story structures, the so-called Case Frame Forest (CFF) isproposed to represent the superficial meaning of story. Based on CFF, a high- dimen-sional grammar, called Forest Grammar (FG), is defined. Furthermore, SPG is definedas a subclass of context-sensitive FG. Considering the context-sensitivity of story con-tent, a type of context-sensitive derivation is defined in the definition of SPG. Lastly,data about runtime efficiency of the syntactic parsing algorithm of weak precedenceSPG, a subclass of SPG, are given and analysed.