Pulsating hydraulic fracturing(PHF)is a promising fracturing method and can generate a dynamic periodic pressure.The periodic pressure can induce fatigue failure of rocks and decrease initiation pressure of fracture.I...Pulsating hydraulic fracturing(PHF)is a promising fracturing method and can generate a dynamic periodic pressure.The periodic pressure can induce fatigue failure of rocks and decrease initiation pressure of fracture.If the frequency of periodic pressure exceeds 10 Hz,the distribution of pressure along the main fracture will be heterogeneous,which is much different from the one induced by the common fracturing method.In this study,the impact of this special spatial feature of pressure on hydraulic fracture is mainly investigated.A coupled numerical simulation model is first proposed and verified through experimental and theoretical solutions.The mechanism of secondary fracture initiation around the main fracture is then discovered.In addition,sensitivity studies are conducted to find out the application potential of this new method.The results show that(1)this coupled numerical simulation model is accurate.Through comparison with experimental and theoretical data,the average error of this coupled model is less than 1.01%.(2)Even if a reservoir has no natural fracture,this heterogeneous distribution pressure can also cause many secondary fractures around the main fracture.(3)The mechanism of secondary fracture initiation is that this heterogeneous distribution pressure causes tensile stress at many locations along the main fracture.(4)Through adjusting the stimulation parameters,the stimulation efficiency can be improved.The average and amplitude of pressure can increase possibility of secondary fracture initiation.The frequency of this periodic pressure can increase number of secondary fractures.Even 6 secondary fractures along a 100 m-length main fracture can be generated.(5)The influence magnitudes of stimulation parameters are larger than ones of geomechanical properties,therefore,this new fracturing method has a wide application potential.展开更多
Laboratory uniaxial compression creep tests,with differential stress of 30 MPa hold for 3 h,were performed on Chang-7,Longmaxi(LMX)and Barnett shales to study the influence of SC-CO_(2)on short-term viscoelastic prope...Laboratory uniaxial compression creep tests,with differential stress of 30 MPa hold for 3 h,were performed on Chang-7,Longmaxi(LMX)and Barnett shales to study the influence of SC-CO_(2)on short-term viscoelastic properties.To this end,the wet shale samples were treated with SC-CO_(2)with a pressure of30 MPa and a temperature of 110℃for 14 days.We analyzed the creep data using the fractional Maxwell model.To investigate microscopic structural alterations,the surface morphology of the same location,before and after SC-CO_(2)-water exposure,was examined by SEM images.Compared with dry shales,dynamic and static elastic moduli decreased by up to 25.02%and 55.83%,respectively,but the creep deformation increased by 200%for LMX and Chang-7 shales,and 500%for the Barnett shale treated by SC-CO_(2).Compared to dry sample,there is an increase in calculated fractional orders of 0.02,0.07,0.22 for SC-CO_(2)treated samples,indicating that SC-CO_(2)treatment is likely to enhance shale creep.SEM investigation confirmed physicochemical mechanisms responsible for the observed elastic damage and creep enhancement,including mineral dissolution and swelling caused by SC-CO_(2).This work would further improve our current understanding of the time-dependent deformation of shale under chemicalmechanical coupling effects during CO_(2)capture utilization and storage.展开更多
Using the particle swarm optimization algorithm on structural search methods, we focus our crystal structures search on boron-rich alkali metal compounds of MB_(12)(M = Be, Mg, Ca, Sr) with simulation cell sizes of 1...Using the particle swarm optimization algorithm on structural search methods, we focus our crystal structures search on boron-rich alkali metal compounds of MB_(12)(M = Be, Mg, Ca, Sr) with simulation cell sizes of 1–2 formula units(f.u.)at 0 GPa. The structure, electronic, and mechanical properties of MB_(12) are obtained from the density functional theory using the plane-wave pseudopotential method within the generalized gradient approximations. The formation enthalpies of MB_(12) regarding to solid metal M and solid alpha-boron suggested the predicted structures can be synthesized except for BeB12. The calculated band structures show MB_(12)(M = Be, Mg, Ca, Sr) are all indirect semiconductors. All the calculated elastic constants of MB_(12) satisfy the the mechanical stable conditions. The mechanical parameters(i.e., bulk modulus,shear modulus, and Young’s modulus) are derived using the Voigt–Reuss–Hill method. The G/B ratios indicated that the MB_(12) should exhibit brittle behavior. In addition, the hardness, Debye temperature, universal anisotropic index, and the percentage of anisotropy in compression and shear are also discussed in detail. We hope our results can inspire further experimental study on these boron-rich alkali-metal compounds.展开更多
Mammalian target of rapamycin(m TOR) inhibitor as an attractive drug target with promising antitumor effects has been widely investigated. High quality clinical trial has been conducted in liver transplant(LT) recipie...Mammalian target of rapamycin(m TOR) inhibitor as an attractive drug target with promising antitumor effects has been widely investigated. High quality clinical trial has been conducted in liver transplant(LT) recipients in Western countries. However, the pertinent studies in Eastern world are paucity. Therefore, we designed a clinical trial to test whether sirolimus can improve recurrence-free survival(RFS) in hepatocellular carcinoma(HCC) patients beyond the Milan criteria after LT. This is an open-labeled, single-arm, prospective, multicenter, and real-world study aiming to evaluate the clinical outcomes of early switch to sirolimus-based regimens in HCC patients after LT. Patients with a histologically proven HCC and beyond the Milan criteria will be enrolled. The initial immunosuppressant regimens are center-specifc for the frst 4-6 weeks. The following regimens integrated sirolimus into the regimens as a combination therapy with reduced calcineurin inhibitors based on the condition of patients and centers. The study is planned for 4 years in total with a 2-year enrollment period and a 2-year follow-up. We predict that sirolimus conversion regimen will provide survival benefts for patients particular in the key indicator RFS as well as better quality of life. If the trial is conducted successfully, we will have a continued monitoring over a longer follow-up time to estimate indicator of overall survival. We hope that the outcome will provide better evidence for clinical decision-making and revising treatment guidelines based on Chinese population data.展开更多
In recent years,the field of deep learning has experienced remarkable growth,leading to the emergence of large,pretrained models such as ChatGPT[1],which demonstrates significant capability in understanding and respon...In recent years,the field of deep learning has experienced remarkable growth,leading to the emergence of large,pretrained models such as ChatGPT[1],which demonstrates significant capability in understanding and responding to human language inputs,and DALL-E[2],which creatively generates images from textual descriptions in a zero-shot manner.展开更多
A dynamic network refers to a graph structure whose nodes and/or links dynamically change over time.Existing visualization and analysis techniques focus mainly on summarizing and revealing the primary evolution patter...A dynamic network refers to a graph structure whose nodes and/or links dynamically change over time.Existing visualization and analysis techniques focus mainly on summarizing and revealing the primary evolution patterns of the network structure.Little work focuses on detecting anomalous changing patterns in the dynamic network,the rare occurrence of which could damage the development of the entire structure.In this study,we introduce the first visual analysis system RCAnalyzer designed for detecting rare changes of sub-structures in a dynamic network.The proposed system employs a rare category detection algorithm to identify anomalous changing structures and visualize them in the context to help oracles examine the analysis results and label the data.In particular,a novel visualization is introduced,which represents the snapshots of a dynamic network in a series of connected triangular matrices.Hierarchical clustering and optimal tree cut are performed on each matrix to illustrate the detected rare change of nodes and links in the context of their surrounding structures.We evaluate our technique via a case study and a user study.The evaluation results verify the effectiveness of our system.展开更多
The structural, electronic, elastic, mechanical properties and stress-strain relationship of chair, boat, and stirrup conformers of fully hydrogenated h-BN(fh-BN) are investigated in this work using the Perdew-Burke-E...The structural, electronic, elastic, mechanical properties and stress-strain relationship of chair, boat, and stirrup conformers of fully hydrogenated h-BN(fh-BN) are investigated in this work using the Perdew-Burke-Ernzerhof(PBE) function in the frame of density functional theory. The achieved results for the lattice parameters and band gaps of three conformers in this research are in good accordance with other theoretical results. The band structures of three conformers show that the chair, boat, and stirrup are direct band gap with a band gaps of(3.12, 4.95, and4.95 e V), respectively. To regulate the band structures of fh-BN, we employ a hybrid functional of Heyd-ScuseriaErnzerhof(HSE06) calculations and the band gaps are 3.84(chair), 6.12(boat), and 6.18 e V(stirrup), respectively.The boat and stirrup fh-BN exhibits varying degrees of mechanical anisotropic properties with respect to the Young's modulus and Poisson's ratio, while the chair fh-BN exhibits the mechanical isotropic properties. Furthermore, tensile strains are applied in the armchair and zigzag directions related to tensile deformation of zigzag and armchair nanotubes,respectively. We find that the ultimate strains in zigzag and armchair deformations in stirrup conformer are 0.34 and0.25, respectively, larger than the strains of zigzag(0.29) and armchair(0.18) deformations in h-BN although h-BN can surstain a surface tension up to the maximum stresses higher than those of three conformers of fh-BN. Furthermore, the band gap energies in three conformers can be modulated effectively with the biaxial tensile strain.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.52004302)Science Foundation of China University of Petroleum,Beijing (No.2462021YXZZ012)the Strategic Cooperation Technology Projects of CNPC and CUPB (ZLZX2020-01)。
文摘Pulsating hydraulic fracturing(PHF)is a promising fracturing method and can generate a dynamic periodic pressure.The periodic pressure can induce fatigue failure of rocks and decrease initiation pressure of fracture.If the frequency of periodic pressure exceeds 10 Hz,the distribution of pressure along the main fracture will be heterogeneous,which is much different from the one induced by the common fracturing method.In this study,the impact of this special spatial feature of pressure on hydraulic fracture is mainly investigated.A coupled numerical simulation model is first proposed and verified through experimental and theoretical solutions.The mechanism of secondary fracture initiation around the main fracture is then discovered.In addition,sensitivity studies are conducted to find out the application potential of this new method.The results show that(1)this coupled numerical simulation model is accurate.Through comparison with experimental and theoretical data,the average error of this coupled model is less than 1.01%.(2)Even if a reservoir has no natural fracture,this heterogeneous distribution pressure can also cause many secondary fractures around the main fracture.(3)The mechanism of secondary fracture initiation is that this heterogeneous distribution pressure causes tensile stress at many locations along the main fracture.(4)Through adjusting the stimulation parameters,the stimulation efficiency can be improved.The average and amplitude of pressure can increase possibility of secondary fracture initiation.The frequency of this periodic pressure can increase number of secondary fractures.Even 6 secondary fractures along a 100 m-length main fracture can be generated.(5)The influence magnitudes of stimulation parameters are larger than ones of geomechanical properties,therefore,this new fracturing method has a wide application potential.
基金support of the National Science Fund for Distinguished Young Scholars(51925405)Beijing Outstanding Young Scientist Program(BJJWZYJH01201911414038)+3 种基金National Natural Science Foundation of China(52104050)National Natural Science Foundation of China(52174011)China Postdoctoral Science Foundation(2021M703579)China University of Petroleum,Beijing(ZX20200119)。
文摘Laboratory uniaxial compression creep tests,with differential stress of 30 MPa hold for 3 h,were performed on Chang-7,Longmaxi(LMX)and Barnett shales to study the influence of SC-CO_(2)on short-term viscoelastic properties.To this end,the wet shale samples were treated with SC-CO_(2)with a pressure of30 MPa and a temperature of 110℃for 14 days.We analyzed the creep data using the fractional Maxwell model.To investigate microscopic structural alterations,the surface morphology of the same location,before and after SC-CO_(2)-water exposure,was examined by SEM images.Compared with dry shales,dynamic and static elastic moduli decreased by up to 25.02%and 55.83%,respectively,but the creep deformation increased by 200%for LMX and Chang-7 shales,and 500%for the Barnett shale treated by SC-CO_(2).Compared to dry sample,there is an increase in calculated fractional orders of 0.02,0.07,0.22 for SC-CO_(2)treated samples,indicating that SC-CO_(2)treatment is likely to enhance shale creep.SEM investigation confirmed physicochemical mechanisms responsible for the observed elastic damage and creep enhancement,including mineral dissolution and swelling caused by SC-CO_(2).This work would further improve our current understanding of the time-dependent deformation of shale under chemicalmechanical coupling effects during CO_(2)capture utilization and storage.
基金Projected supported by the National Natural Science Foundation of China(Grant Nos.U1904179,U1904178,and 51501093)the Key Science Fund of Educational Department of Henan Province,China(Grant Nos.19A140013 and 20B140010)the Science Technology Innovation Talents Fund in Universities of Henan Province,China(Grant No.19HASTIT019)。
文摘Using the particle swarm optimization algorithm on structural search methods, we focus our crystal structures search on boron-rich alkali metal compounds of MB_(12)(M = Be, Mg, Ca, Sr) with simulation cell sizes of 1–2 formula units(f.u.)at 0 GPa. The structure, electronic, and mechanical properties of MB_(12) are obtained from the density functional theory using the plane-wave pseudopotential method within the generalized gradient approximations. The formation enthalpies of MB_(12) regarding to solid metal M and solid alpha-boron suggested the predicted structures can be synthesized except for BeB12. The calculated band structures show MB_(12)(M = Be, Mg, Ca, Sr) are all indirect semiconductors. All the calculated elastic constants of MB_(12) satisfy the the mechanical stable conditions. The mechanical parameters(i.e., bulk modulus,shear modulus, and Young’s modulus) are derived using the Voigt–Reuss–Hill method. The G/B ratios indicated that the MB_(12) should exhibit brittle behavior. In addition, the hardness, Debye temperature, universal anisotropic index, and the percentage of anisotropy in compression and shear are also discussed in detail. We hope our results can inspire further experimental study on these boron-rich alkali-metal compounds.
基金supported by grants from the National S&T Major Project (2017ZX10203205)Key Program,National Natural Science Foundation of China (81930016)Zhejiang Provincial Natural Science Foundation of China (LY21H160026)。
文摘Mammalian target of rapamycin(m TOR) inhibitor as an attractive drug target with promising antitumor effects has been widely investigated. High quality clinical trial has been conducted in liver transplant(LT) recipients in Western countries. However, the pertinent studies in Eastern world are paucity. Therefore, we designed a clinical trial to test whether sirolimus can improve recurrence-free survival(RFS) in hepatocellular carcinoma(HCC) patients beyond the Milan criteria after LT. This is an open-labeled, single-arm, prospective, multicenter, and real-world study aiming to evaluate the clinical outcomes of early switch to sirolimus-based regimens in HCC patients after LT. Patients with a histologically proven HCC and beyond the Milan criteria will be enrolled. The initial immunosuppressant regimens are center-specifc for the frst 4-6 weeks. The following regimens integrated sirolimus into the regimens as a combination therapy with reduced calcineurin inhibitors based on the condition of patients and centers. The study is planned for 4 years in total with a 2-year enrollment period and a 2-year follow-up. We predict that sirolimus conversion regimen will provide survival benefts for patients particular in the key indicator RFS as well as better quality of life. If the trial is conducted successfully, we will have a continued monitoring over a longer follow-up time to estimate indicator of overall survival. We hope that the outcome will provide better evidence for clinical decision-making and revising treatment guidelines based on Chinese population data.
基金This work was partially supported by the National Science and Technology Major Project(2022ZD0114805)the National Natural Science Foundation of China(Grant Nos.62376118,62006112,62250069,61921006)the Collaborative Innovation Center of Novel Software Technology and Industrialization.
文摘In recent years,the field of deep learning has experienced remarkable growth,leading to the emergence of large,pretrained models such as ChatGPT[1],which demonstrates significant capability in understanding and responding to human language inputs,and DALL-E[2],which creatively generates images from textual descriptions in a zero-shot manner.
基金Project supported by the National Natural Science Foundation of China(Nos.U1866602,61772456,U1736109,and 61972122)。
文摘A dynamic network refers to a graph structure whose nodes and/or links dynamically change over time.Existing visualization and analysis techniques focus mainly on summarizing and revealing the primary evolution patterns of the network structure.Little work focuses on detecting anomalous changing patterns in the dynamic network,the rare occurrence of which could damage the development of the entire structure.In this study,we introduce the first visual analysis system RCAnalyzer designed for detecting rare changes of sub-structures in a dynamic network.The proposed system employs a rare category detection algorithm to identify anomalous changing structures and visualize them in the context to help oracles examine the analysis results and label the data.In particular,a novel visualization is introduced,which represents the snapshots of a dynamic network in a series of connected triangular matrices.Hierarchical clustering and optimal tree cut are performed on each matrix to illustrate the detected rare change of nodes and links in the context of their surrounding structures.We evaluate our technique via a case study and a user study.The evaluation results verify the effectiveness of our system.
基金Supported by the Henan Joint Funds of the National Natural Science Foundation of China under Grant No.U1404608the National Natural Science Foundation of China under Grant No.51501093the Key Science Fund of Educational Department of Henan Province of China under Grant No.20B140010
文摘The structural, electronic, elastic, mechanical properties and stress-strain relationship of chair, boat, and stirrup conformers of fully hydrogenated h-BN(fh-BN) are investigated in this work using the Perdew-Burke-Ernzerhof(PBE) function in the frame of density functional theory. The achieved results for the lattice parameters and band gaps of three conformers in this research are in good accordance with other theoretical results. The band structures of three conformers show that the chair, boat, and stirrup are direct band gap with a band gaps of(3.12, 4.95, and4.95 e V), respectively. To regulate the band structures of fh-BN, we employ a hybrid functional of Heyd-ScuseriaErnzerhof(HSE06) calculations and the band gaps are 3.84(chair), 6.12(boat), and 6.18 e V(stirrup), respectively.The boat and stirrup fh-BN exhibits varying degrees of mechanical anisotropic properties with respect to the Young's modulus and Poisson's ratio, while the chair fh-BN exhibits the mechanical isotropic properties. Furthermore, tensile strains are applied in the armchair and zigzag directions related to tensile deformation of zigzag and armchair nanotubes,respectively. We find that the ultimate strains in zigzag and armchair deformations in stirrup conformer are 0.34 and0.25, respectively, larger than the strains of zigzag(0.29) and armchair(0.18) deformations in h-BN although h-BN can surstain a surface tension up to the maximum stresses higher than those of three conformers of fh-BN. Furthermore, the band gap energies in three conformers can be modulated effectively with the biaxial tensile strain.
