In this study,the moment tensor of transversely isotropic shale was analyzed using a discrete element method-acoustic emission model(DEM-AE model).Firstly,the failure modes of the shale obtained from the acoustic emis...In this study,the moment tensor of transversely isotropic shale was analyzed using a discrete element method-acoustic emission model(DEM-AE model).Firstly,the failure modes of the shale obtained from the acoustic emission(AE) events and physical experiments were compared.Secondly,the relationships between AE events and seismic magnitudes,and AE events and the resulting cracks were analyzed.Finally,a moment tensor T-k chart describing the seismic source was introduced to demonstrate the differences in the transversely isotropic shale.The results showed that,for different anisotropy angles,a linear logarithmic relationship existed between the cumulative AE events and the seismic magnitude in the concentration area of the AE events.A normal distribution was observed for the number of AE events as the seismic magnitude changed from small to large.The moment tensor T-k chart indicated that the number and proportion of linear tension cracks in the shale were highest.When θ = 30°,the peak seismic magnitude was at a minimum.The average seismic magnitude in the concentration area of the AE events was also relatively small.Points close to the U=-1/3V line and the number of cracks included in a single AE event were at a minimum,and the corresponding peak stress also reached its lowest level.In contrast,when θ=90°,all related parameters were contrary to the above θ = 30° case.The DEM-AE model and the moment tensor T-k chart are suitable for analyzing the distribution of shale cracks appearing during the loading process.This study can provide constructive references for future research on the fracturing treatment of shale.展开更多
Central Asia is emerging as an important pole of global economic and political power,thanks to its unique location at the heart of Eurasia and its abundance in energy reserves.This study explores the social power chan...Central Asia is emerging as an important pole of global economic and political power,thanks to its unique location at the heart of Eurasia and its abundance in energy reserves.This study explores the social power change in Central Asia from the perspective of cross-border mergers and acquisitions(M&A)by using the social network method.The main results are as follows:(1)The complexity of the energy M&A network has significantly decreased after the financial crisis in 2008.In the meantime,energy M&A became an important way to enhance energy power for buyer countries.Betweenness centrality is becoming the most significant factor affecting energy power,yet the effect of out-degree is weakening.(2)The community underwent multifaceted restructuring,which reflected the shift of energy power in Central Asia.Kazakhstan is the most powerful country in the energy sector in Central Asia.In addition,East Asian countries/regions,represented by China,are actively enhancing their energy power.(3)Different M&A modes reflect various M&A motivations of countries in the energy sector.In the future,more efforts should be made to promote the establishment of a pragmatic and efficient multilateral energy cooperation mechanism and strength the cooperation of the economy and energy finance when China participates in the energy market in Central Asia.展开更多
基金Financial support for this work is provided by the National Natural Science Foundation of China (no.51474208)the National Key Research and Development Program of China (2016YFC0600904)+1 种基金a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)The fnancial support provided by China Scholarship Council (CSC,Grant no.201606420013)
文摘In this study,the moment tensor of transversely isotropic shale was analyzed using a discrete element method-acoustic emission model(DEM-AE model).Firstly,the failure modes of the shale obtained from the acoustic emission(AE) events and physical experiments were compared.Secondly,the relationships between AE events and seismic magnitudes,and AE events and the resulting cracks were analyzed.Finally,a moment tensor T-k chart describing the seismic source was introduced to demonstrate the differences in the transversely isotropic shale.The results showed that,for different anisotropy angles,a linear logarithmic relationship existed between the cumulative AE events and the seismic magnitude in the concentration area of the AE events.A normal distribution was observed for the number of AE events as the seismic magnitude changed from small to large.The moment tensor T-k chart indicated that the number and proportion of linear tension cracks in the shale were highest.When θ = 30°,the peak seismic magnitude was at a minimum.The average seismic magnitude in the concentration area of the AE events was also relatively small.Points close to the U=-1/3V line and the number of cracks included in a single AE event were at a minimum,and the corresponding peak stress also reached its lowest level.In contrast,when θ=90°,all related parameters were contrary to the above θ = 30° case.The DEM-AE model and the moment tensor T-k chart are suitable for analyzing the distribution of shale cracks appearing during the loading process.This study can provide constructive references for future research on the fracturing treatment of shale.
基金The Strategic Priority Research of the CAS,No.XDA20040400National Natural Science Foundation of China,No.41871118,No.42022007China Scholarship Council,No.201904910633。
文摘Central Asia is emerging as an important pole of global economic and political power,thanks to its unique location at the heart of Eurasia and its abundance in energy reserves.This study explores the social power change in Central Asia from the perspective of cross-border mergers and acquisitions(M&A)by using the social network method.The main results are as follows:(1)The complexity of the energy M&A network has significantly decreased after the financial crisis in 2008.In the meantime,energy M&A became an important way to enhance energy power for buyer countries.Betweenness centrality is becoming the most significant factor affecting energy power,yet the effect of out-degree is weakening.(2)The community underwent multifaceted restructuring,which reflected the shift of energy power in Central Asia.Kazakhstan is the most powerful country in the energy sector in Central Asia.In addition,East Asian countries/regions,represented by China,are actively enhancing their energy power.(3)Different M&A modes reflect various M&A motivations of countries in the energy sector.In the future,more efforts should be made to promote the establishment of a pragmatic and efficient multilateral energy cooperation mechanism and strength the cooperation of the economy and energy finance when China participates in the energy market in Central Asia.
