Gaokao, the college/university entrance examination, has been playing a decisive role in the access of higher education in China since 1949. This high-stakes examination has received increasing criticisms these years ...Gaokao, the college/university entrance examination, has been playing a decisive role in the access of higher education in China since 1949. This high-stakes examination has received increasing criticisms these years about the contents and forms of the exam. This article briefly examines the development of Gaokao, and focuses on the equity of educational opportunities the examinees can have in different provinces and rural and urban areas, which is the critical way to individual success and the promotion of social mobility. There is inequity of educational opportunities in different provinces as well as the rural and urban areas. The Ministry of Education (MoE) in China has adopted optional examination approaches, inequity, however, arises in them too. Remedial reform is implemented and Gaokao at present is still the effective system while optional system is available.展开更多
The phylogenetic origin of Beckmannia remains unknown. The genus has been placed within the Chlorideae, Aveneae （Agrostideae）, Poeae, or treated as an isolate lineage, Beckmanniinae. In the present study, we used nu...The phylogenetic origin of Beckmannia remains unknown. The genus has been placed within the Chlorideae, Aveneae （Agrostideae）, Poeae, or treated as an isolate lineage, Beckmanniinae. In the present study, we used nuclear internal transcribed spacer （ITS） and chloroplast trnL-F sequences to examine the phylogenetic relationship between Beckmannia and those genera that have assumed to be related. On the basis of the results of our studies, the following conclusions could be drawn： （i） Beckmannia and Alopecurus are sister groups with high support; and （ii） Beckmannia and Alopecurus are nested in the Poeae clade with high support. The results of our analysis suggest that Beckmannia should be placed in Poeae.展开更多
In order to overcome serious instability prob- lems in hydratable shale formations, a novel electropositive wellbore stabilizer （EPWS） was prepared by a new approach. It has good colloidal stability, particle size d...In order to overcome serious instability prob- lems in hydratable shale formations, a novel electropositive wellbore stabilizer （EPWS） was prepared by a new approach. It has good colloidal stability, particle size dis- tribution, compatibility, sealing property, and flexible adaptability. A variety of methods including measurements of particle size, Zeta potential, colloidal stability, contact angle, shale stability index, shale dispersion, shale swelling, and plugging experiments were adopted to characterize the EPWS and evaluate its anti-sloughing capacity and flexible adaptability. Results show that the EPWS has advantages over the conventional wellbore stabilizer （ZX-3） in particle size distribution, colloidal stability, inhibition, compatibil- ity, and flexible adaptability. The EPWS with an average particle size of 507 nm and an average Zeta potential of 54 mV could be stable for 147 days and be compatible with salt tolerant or positive charged additives, and it also exhibited preferable anti-sloughing performance to hydrat- able shales at 77, 100, and 120 ~C, and better compatibility with sodium bentonite than ZX-3 and KC1. The EPWS can plug micro-fractures and pores by forming a tight external mud cake and an internal sealing belt to retard pressure transmission and prevent filtrate invasion, enhancing hydrophobicity of shale surfaces by adsorption to inhibithydration. The EPWS with flexible adaptability to tem- perature for inhibition and sealing capacity is available for long open-hole sections during drilling.展开更多
Pseudo three-dimension (P3D) hydraulic fracturing models often overpredict the fracture height for a poorly contained fracture. To solve this problem, a new method is presented in shaping the P3D fracture geometry on ...Pseudo three-dimension (P3D) hydraulic fracturing models often overpredict the fracture height for a poorly contained fracture. To solve this problem, a new method is presented in shaping the P3D fracture geometry on the basis of the fundamental theory and the original 1D fluid flow is replaced with a more representatively radial flow. The distribution of the fluid in the modified fluid field is analyzed and a sound explanation to the problem is given. Due to the consideration of the fluid flow in the vertical direction, the modified model can predict the fracture height much better. To validate the rationality of the radial fluid flow assumption, the distribution of the fluid in the modified fluid field is simulated with the plane potential flow by using finite element method. And the results agree effectively with those from the assumption. Through comparing with the full 3D model, the results show that this new P3D model can be used to aid the fracturing design and predict the fracture height under poorly contained situation.展开更多
文摘Gaokao, the college/university entrance examination, has been playing a decisive role in the access of higher education in China since 1949. This high-stakes examination has received increasing criticisms these years about the contents and forms of the exam. This article briefly examines the development of Gaokao, and focuses on the equity of educational opportunities the examinees can have in different provinces and rural and urban areas, which is the critical way to individual success and the promotion of social mobility. There is inequity of educational opportunities in different provinces as well as the rural and urban areas. The Ministry of Education (MoE) in China has adopted optional examination approaches, inequity, however, arises in them too. Remedial reform is implemented and Gaokao at present is still the effective system while optional system is available.
基金supported b ythe National Natural Science Foundation of China(30270107)the Project Sponsored by the Scientific Research Foundation for the Doctors,Weifang Medical University
文摘The phylogenetic origin of Beckmannia remains unknown. The genus has been placed within the Chlorideae, Aveneae （Agrostideae）, Poeae, or treated as an isolate lineage, Beckmanniinae. In the present study, we used nuclear internal transcribed spacer （ITS） and chloroplast trnL-F sequences to examine the phylogenetic relationship between Beckmannia and those genera that have assumed to be related. On the basis of the results of our studies, the following conclusions could be drawn： （i） Beckmannia and Alopecurus are sister groups with high support; and （ii） Beckmannia and Alopecurus are nested in the Poeae clade with high support. The results of our analysis suggest that Beckmannia should be placed in Poeae.
基金financially supported by the National Science Foundation of China (No.51374233)Shandong Province Science Foundation (No.ZR2013EEM032)+1 种基金the Fundamental Research Funds for the Central Universities (No.13CX02044A)the Project of China Scholarship Council (201306455021)
文摘In order to overcome serious instability prob- lems in hydratable shale formations, a novel electropositive wellbore stabilizer （EPWS） was prepared by a new approach. It has good colloidal stability, particle size dis- tribution, compatibility, sealing property, and flexible adaptability. A variety of methods including measurements of particle size, Zeta potential, colloidal stability, contact angle, shale stability index, shale dispersion, shale swelling, and plugging experiments were adopted to characterize the EPWS and evaluate its anti-sloughing capacity and flexible adaptability. Results show that the EPWS has advantages over the conventional wellbore stabilizer （ZX-3） in particle size distribution, colloidal stability, inhibition, compatibil- ity, and flexible adaptability. The EPWS with an average particle size of 507 nm and an average Zeta potential of 54 mV could be stable for 147 days and be compatible with salt tolerant or positive charged additives, and it also exhibited preferable anti-sloughing performance to hydrat- able shales at 77, 100, and 120 ~C, and better compatibility with sodium bentonite than ZX-3 and KC1. The EPWS can plug micro-fractures and pores by forming a tight external mud cake and an internal sealing belt to retard pressure transmission and prevent filtrate invasion, enhancing hydrophobicity of shale surfaces by adsorption to inhibithydration. The EPWS with flexible adaptability to tem- perature for inhibition and sealing capacity is available for long open-hole sections during drilling.
文摘Pseudo three-dimension (P3D) hydraulic fracturing models often overpredict the fracture height for a poorly contained fracture. To solve this problem, a new method is presented in shaping the P3D fracture geometry on the basis of the fundamental theory and the original 1D fluid flow is replaced with a more representatively radial flow. The distribution of the fluid in the modified fluid field is analyzed and a sound explanation to the problem is given. Due to the consideration of the fluid flow in the vertical direction, the modified model can predict the fracture height much better. To validate the rationality of the radial fluid flow assumption, the distribution of the fluid in the modified fluid field is simulated with the plane potential flow by using finite element method. And the results agree effectively with those from the assumption. Through comparing with the full 3D model, the results show that this new P3D model can be used to aid the fracturing design and predict the fracture height under poorly contained situation.
