The evolution of cracks in shale directly affects the efficient production of shale gas.However,there is a lack of research on the characteristics of crack initiation in deep dense shale under different stress conditi...The evolution of cracks in shale directly affects the efficient production of shale gas.However,there is a lack of research on the characteristics of crack initiation in deep dense shale under different stress conditions.In this work,considering the different combinations of confining pressure and bedding plane inclination angle(α),biaxial mechanical loading experiments were conducted on shale containing circular holes.The research results indicate that the confining pressure and inclination angle of the bedding planes significantly influence the failure patterns of shale containing circular holes.The instability of shale containing circular holes can be classified into five types:tensile failure along the bedding planes,tensile failure through the bedding planes,shear slip along the bedding planes,shear failure through the bedding planes,and block instability failure.Furthermore,the evolution of strain and stress fields around the circular holes was found to be the fundamental cause of variations in the initiation characteristics and locations of shale cracks.The crack initiation criterion for shale containing circular hole was established,providing a new method for evaluating the trajectory of shale hole wall fractures.This study holds significant importance for evaluating the evolution and stability of fracture networks within shale reservoirs.展开更多
Objective To explore the distribution and characteristics of initial PSA and PSA velocity in men younger than years without prostate cancer. Methods PSA in men younger than 50 years without prostate cancer from Januar...Objective To explore the distribution and characteristics of initial PSA and PSA velocity in men younger than years without prostate cancer. Methods PSA in men younger than 50 years without prostate cancer from January 2001 to November 2009 were retrieved retrospec-展开更多
In this paper,the flow field characteristics of Oblique Detonation Waves(ODWs)induced by a finite wedge under argon dilution are studied by solving the Euler equations with a detailed chemical model of hydrogen and ai...In this paper,the flow field characteristics of Oblique Detonation Waves(ODWs)induced by a finite wedge under argon dilution are studied by solving the Euler equations with a detailed chemical model of hydrogen and air.First,the effects of the expansion waves,argon concentration,geometric parameters,and Mach number on the ODW are discussed.The results show that the changes of these parameters may make the oblique detonation not be initiated.Then,the ODW initiation criterion of the finite wedge is summarized,as the characteristic length of the induction zone LCand the characteristic length of the oblique wedge LWmeet the condition LC/LW<1,the initiation of the ODW occurs;otherwise,it does not occur.What’s more,the Constant Volume Combustion(CVC)theory is applied to study the characteristic length of induction zone.It is found that CVC theory is more suitable for the“smooth transition”type of ODW flow field,the theoretical and numerical characteristic length in induction regions are in good agreement.This work is of great significance for the design of oblique detonation engines for hypersonic vehicles.展开更多
The characteristics of fatigue crack initiation in Ti-5AI-4Sn-2Zr1Mo-O.7Nd-O.25Si alloy wereStudied. Two modes Of fatigue crack initiation were found. The Nd-rich phase particles displaybetter resistance to fatigue cr...The characteristics of fatigue crack initiation in Ti-5AI-4Sn-2Zr1Mo-O.7Nd-O.25Si alloy wereStudied. Two modes Of fatigue crack initiation were found. The Nd-rich phase particles displaybetter resistance to fatigue crack initiation than the matrix at lower stress.展开更多
The upward lightning(UL) initiated from the top of tall buildings(at least above 100 m) is a type of atmospheric discharge. Currently, we understand the nature of the UL from ground observations, but the corresponding...The upward lightning(UL) initiated from the top of tall buildings(at least above 100 m) is a type of atmospheric discharge. Currently, we understand the nature of the UL from ground observations, but the corresponding theoretical research is lacking. Based on an existing bidirectional leader stochastic model, a stochastic parameterization scheme for the UL has been built and embedded in an existing two-dimensional thundercloud charge/discharge model. The ULs simulated from the experiments with two-dimensional high resolution agree generally with the observation results. By analyzing the charge structure of thunderstorm clouds, we determined the in-cloud environmental characteristics that favor the initiation of conventional cloud-to-ground(CG) flashes and analyzed the differences and similarities of some characteristics of the positive and the negative UL. Simulation results indicate that the positive ULs are typically other-lightning-triggered ULs(OLTUL) and are usually a discharge phenomenon between the ground and the lower positive charge region appearing below the main middle negative charge region. The effect of the previous in-cloud lightning(IC) process of space electrical field provides favorable conditions for the initiation of a positive UL. Its entire discharge process is limited, and the branches of the leader are fewer in number as its discharge is not sufficient. A negative UL is generally a discharge phenomenon of the dipole charge structure between the ground and the main negative charge region. The lower temperature stratification and the sinking of the hydrometeors typically initiate a negative UL. Negative ULs develop strongly and have more branches. The OLTUL is initiated mainly during the development stage of a thunderstorm, while the self-triggered UL(STUL) is initiated mainly during the dissipation stage of a thunderstorm.展开更多
The CSU-RAMS-2A was used to simulate the meteorological fields over the Zhujiang River Delta in South China. Initialized from a horizontally homogeneous atmosphere,real topography and inhomogeneous surface boundary co...The CSU-RAMS-2A was used to simulate the meteorological fields over the Zhujiang River Delta in South China. Initialized from a horizontally homogeneous atmosphere,real topography and inhomogeneous surface boundary condi- tions,the model was run with thermal and terrain forcing.The modeling results of winter and summer cases are com- pared with those observed.The similarity of the predicted distributions of winds,temperatures and humidities to the ob- served patterns permits us to conclude that the mesoscale distribution of meteorological elements for the two study dates is the result of the thermal and dynamical forcing by the underlying surface and topography.展开更多
This paper deals with the optimal transportation for generalized Lagrangian L = L（x, u, t）, and considers the following cost function： c（x, y） = inf x（0）=x x（1）=y u∈U∫0^1 L（x（s）, u（x（s）, s）, s）ds, w...This paper deals with the optimal transportation for generalized Lagrangian L = L（x, u, t）, and considers the following cost function： c（x, y） = inf x（0）=x x（1）=y u∈U∫0^1 L（x（s）, u（x（s）, s）, s）ds, where U is a control set, and x satisfies the ordinary equation x（s） = f（x（s）, u（x（s）, s））.It is proved that under the condition that the initial measure μ0 is absolutely continuous w.r.t. the Lebesgue measure, the Monge problem has a solution, and the optimal transport map just walks along the characteristic curves of the corresponding Hamilton-Jacobi equation：Vt（t, x） ＋ sup u∈U = 0,V（0, x） = Φ0（x）.展开更多
基金Projects(52104143,52109135,52374099)supported by the National Natural Science Foundation of ChinaProject(2025YFHZ0323)supported by the Natural Science Foundation of Sichuan Province,China。
文摘The evolution of cracks in shale directly affects the efficient production of shale gas.However,there is a lack of research on the characteristics of crack initiation in deep dense shale under different stress conditions.In this work,considering the different combinations of confining pressure and bedding plane inclination angle(α),biaxial mechanical loading experiments were conducted on shale containing circular holes.The research results indicate that the confining pressure and inclination angle of the bedding planes significantly influence the failure patterns of shale containing circular holes.The instability of shale containing circular holes can be classified into five types:tensile failure along the bedding planes,tensile failure through the bedding planes,shear slip along the bedding planes,shear failure through the bedding planes,and block instability failure.Furthermore,the evolution of strain and stress fields around the circular holes was found to be the fundamental cause of variations in the initiation characteristics and locations of shale cracks.The crack initiation criterion for shale containing circular hole was established,providing a new method for evaluating the trajectory of shale hole wall fractures.This study holds significant importance for evaluating the evolution and stability of fracture networks within shale reservoirs.
文摘Objective To explore the distribution and characteristics of initial PSA and PSA velocity in men younger than years without prostate cancer. Methods PSA in men younger than 50 years without prostate cancer from January 2001 to November 2009 were retrieved retrospec-
基金supported by the Fundamental Research Funds for the Central Universities of China(No.310201906zy009)the Basic Research Plan of Natural Science in Shanxi Province—General Project(Youth),China(No.2019JQ-132)。
文摘In this paper,the flow field characteristics of Oblique Detonation Waves(ODWs)induced by a finite wedge under argon dilution are studied by solving the Euler equations with a detailed chemical model of hydrogen and air.First,the effects of the expansion waves,argon concentration,geometric parameters,and Mach number on the ODW are discussed.The results show that the changes of these parameters may make the oblique detonation not be initiated.Then,the ODW initiation criterion of the finite wedge is summarized,as the characteristic length of the induction zone LCand the characteristic length of the oblique wedge LWmeet the condition LC/LW<1,the initiation of the ODW occurs;otherwise,it does not occur.What’s more,the Constant Volume Combustion(CVC)theory is applied to study the characteristic length of induction zone.It is found that CVC theory is more suitable for the“smooth transition”type of ODW flow field,the theoretical and numerical characteristic length in induction regions are in good agreement.This work is of great significance for the design of oblique detonation engines for hypersonic vehicles.
文摘The characteristics of fatigue crack initiation in Ti-5AI-4Sn-2Zr1Mo-O.7Nd-O.25Si alloy wereStudied. Two modes Of fatigue crack initiation were found. The Nd-rich phase particles displaybetter resistance to fatigue crack initiation than the matrix at lower stress.
基金supported by the Guangdong Basic and Applied Basic research Foundation (Grant No.2022A1515011565)Foundation of State Key Laboratory of High Temperature Gas Dynamics (Grant No.2021KF10)the China Postdoctoral Science Foundation (Grant Nos.2021M692633 and 2022T150534).
基金supported by the National Key Basic Research Development Program of China (Grant No. 2014CB441403)the National Natural Science Foundation of China (Grant Nos. 41175003 & 41475003)
文摘The upward lightning(UL) initiated from the top of tall buildings(at least above 100 m) is a type of atmospheric discharge. Currently, we understand the nature of the UL from ground observations, but the corresponding theoretical research is lacking. Based on an existing bidirectional leader stochastic model, a stochastic parameterization scheme for the UL has been built and embedded in an existing two-dimensional thundercloud charge/discharge model. The ULs simulated from the experiments with two-dimensional high resolution agree generally with the observation results. By analyzing the charge structure of thunderstorm clouds, we determined the in-cloud environmental characteristics that favor the initiation of conventional cloud-to-ground(CG) flashes and analyzed the differences and similarities of some characteristics of the positive and the negative UL. Simulation results indicate that the positive ULs are typically other-lightning-triggered ULs(OLTUL) and are usually a discharge phenomenon between the ground and the lower positive charge region appearing below the main middle negative charge region. The effect of the previous in-cloud lightning(IC) process of space electrical field provides favorable conditions for the initiation of a positive UL. Its entire discharge process is limited, and the branches of the leader are fewer in number as its discharge is not sufficient. A negative UL is generally a discharge phenomenon of the dipole charge structure between the ground and the main negative charge region. The lower temperature stratification and the sinking of the hydrometeors typically initiate a negative UL. Negative ULs develop strongly and have more branches. The OLTUL is initiated mainly during the development stage of a thunderstorm, while the self-triggered UL(STUL) is initiated mainly during the dissipation stage of a thunderstorm.
文摘The CSU-RAMS-2A was used to simulate the meteorological fields over the Zhujiang River Delta in South China. Initialized from a horizontally homogeneous atmosphere,real topography and inhomogeneous surface boundary condi- tions,the model was run with thermal and terrain forcing.The modeling results of winter and summer cases are com- pared with those observed.The similarity of the predicted distributions of winds,temperatures and humidities to the ob- served patterns permits us to conclude that the mesoscale distribution of meteorological elements for the two study dates is the result of the thermal and dynamical forcing by the underlying surface and topography.
文摘This paper deals with the optimal transportation for generalized Lagrangian L = L（x, u, t）, and considers the following cost function： c（x, y） = inf x（0）=x x（1）=y u∈U∫0^1 L（x（s）, u（x（s）, s）, s）ds, where U is a control set, and x satisfies the ordinary equation x（s） = f（x（s）, u（x（s）, s））.It is proved that under the condition that the initial measure μ0 is absolutely continuous w.r.t. the Lebesgue measure, the Monge problem has a solution, and the optimal transport map just walks along the characteristic curves of the corresponding Hamilton-Jacobi equation：Vt（t, x） ＋ sup u∈U = 0,V（0, x） = Φ0（x）.
