During the operational process of natural gas gathering and transmission pipelines,the formation of hydrates is highly probable,leading to uncontrolled movement and aggregation of hydrates.The continuous migration and...During the operational process of natural gas gathering and transmission pipelines,the formation of hydrates is highly probable,leading to uncontrolled movement and aggregation of hydrates.The continuous migration and accumulation of hydrates further contribute to the obstruction of natural gas pipelines,resulting in production reduction,shutdowns,and pressure build-ups.Consequently,a cascade of risks is prone to occur.To address this issue,this study focuses on the operational process of natural gas gathering and transmission pipelines,where a comprehensive framework is established.This framework includes theoretical models for pipeline temperature distribution,pipeline pressure distribution,multiphase flow within the pipeline,hydrate blockage,and numerical solution methods.By analyzing the influence of inlet temperature,inlet pressure,and terminal pressure on hydrate formation within the pipeline,the sensitivity patterns of hydrate blockage risks are derived.The research indicates that reducing inlet pressure and terminal pressure could lead to a decreased maximum hydrate formation rate,potentially mitigating pipeline blockage during natural gas transportation.Furthermore,an increase in inlet temperature and terminal pressure,and a decrease in inlet pressure,results in a displacement of the most probable location for hydrate blockage towards the terminal station.However,it is crucial to note that operating under low-pressure conditions significantly elevates energy consumption within the gathering system,contradicting the operational goal of energy efficiency and reduction of energy consumption.Consequently,for high-pressure gathering pipelines,measures such as raising the inlet temperature or employing inhibitors,electrical heat tracing,and thermal insulation should be adopted to prevent hydrate formation during natural gas transportation.Moreover,considering abnormal conditions such as gas well production and pipeline network shutdowns,which could potentially trigger hydrate formation,the installation of methanol injection connectors remains necessary to ensure production safety.展开更多
The casing deformation prevention technology based on the optimization of cement slurry is proposed to reduce the casing deformation of shale oil and gas wells during hydraulic fracturing. In this paper, the fracture ...The casing deformation prevention technology based on the optimization of cement slurry is proposed to reduce the casing deformation of shale oil and gas wells during hydraulic fracturing. In this paper, the fracture mechanism of hollow particles in cement sheath was firstly analyzed by discrete element method, and the effect of hollow particles in cement on casing deformation was investigated by laboratory experiment method. Finally, field test was carried out to verify the improvement effect of the casing deformation based on cement slurry modification. The results show that the formation displacement can be absorbed effectively by hollow particles inside the cement transferring the excessive deformation away from casing. The particles in the uncemented state provide deformation space during formation slipping. The casing with diameter of 139.7 mm could be passed through by bridge plug with the diameter of 99 mm when the mass ratio of particle/cement reaches 1:4. According to the field test feedback, the method based on optimization of cement slurry can effectively reduce the risk of casing deformation, and the recommended range of hollow microbeads content in the cement slurry is between 15% and 25%.展开更多
Coronary artery calcification （CAC） is highly prevalent in patients with coronary heart disease （CHD） and is associated with major adverse cardiovascular events. There are two recognized type of CAC--intimal and m...Coronary artery calcification （CAC） is highly prevalent in patients with coronary heart disease （CHD） and is associated with major adverse cardiovascular events. There are two recognized type of CAC--intimal and medial calcification, and each of them have specific risk factors. Several theories about the mechanism of vascular calcification have been put forward, and we currently believe that vascular calcification is an active, regulated process. CAC can usually be found in patients with severe CHD, and this asymptomatic phenomenon make early diagnosis of CAC important. Coronary computed tomographic angiography is the main noninvasive tool to detect calcified lesions. Measurement of coronary artery calcification by scoring is a reasonable metric for cardiovascular risk assessment in asymptomatic adults at intermediate risk. To date, effective medical treatment of CAC has not been identified. Several strategies of percutaneous coronary interven- tion have been applied to CHD patients with CAC, but with unsatisfactory results. Prognosis of CAC is still a major problem of CHD pa- tients. Thus, more details about the mechanisms of CAC need to be elucidated in order to improve the understanding and treatment of CAC.展开更多
Gecko-like robot（Geckobot）,an important branch of bionic robotics,is a robot that simulates gecko＇s capacity to climb walls and ceilings.The work environment of the traditional wall-climbing robot is greatly limite...Gecko-like robot（Geckobot）,an important branch of bionic robotics,is a robot that simulates gecko＇s capacity to climb walls and ceilings.The work environment of the traditional wall-climbing robot is greatly limited as the moving structure and adsorption principle of the robot have nothing to do with the real gecko.However,the adsorption principle and moving mode of the real gecko can provide a new way to break through the restrictions of the traditional wall-climbing robot.Inspired by the moving mechanism of geckos, this paper develops the Geckobot with motile body.Two types of Geckobots are addressed：one with compliant flat bar as the body,and the other with prismatic joint as the body.The compliant body not only resembles the moving mode of the real gecko body,but also simplifies the Geckobot＇s structure.The prismatic joint body is used to adapt the change of body length in ground-to-wall transition. The gait planning on the plane and the transition between perpendicular intersectional planes is discussed,with an emphasis on the analysis of the kinematics degree of freedom（DOF） and body posture.Central pattern generator（CPG） neural network is realized in LabVIEW and utilized to control Geckobot＇s movement.The CPG scheme in Lab VIEW is given,and how CPG is used to control Geckobot to turn or move forward is explored.Simulations are conducted in ADAMS to verify the feasibility of the structure design and gait planning and to acquire some parameters for practical Geckobot development.The experiment with Geckobot-Ⅰand Geckobot-Ⅱon their crawling capacity on the plane and the ground-to-wall transition finds that the robot can complete the crawling movement and ground-to-wall transition,verifying the feasibility of the structure design,gait planning and the CPG motion control.The Geckobot structure design approach,gait planning and the CPG motion control presented would be useful for the research on wall-climbing robots.展开更多
BACKGROUND A growing amount of evidence provides support for the hypothesis that acute myocardial infarction(AMI)patients should go through cardiopulmonary exercise testing(CPET)about 3-5 d after AMI is diagnosed,make...BACKGROUND A growing amount of evidence provides support for the hypothesis that acute myocardial infarction(AMI)patients should go through cardiopulmonary exercise testing(CPET)about 3-5 d after AMI is diagnosed,make reasonable exercising prescription,and conduct exercise training under guidance.AIM To investigate the effect of exercise training(ET)on left ventricular systolic function and left ventricular remodeling(LVRM)and to study the possible mechanisms of LVRM by the changes of matrix metallopeptidase 9(MMP-9)and tissue inhibitor of metalloproteinases 1(TIMP-1)in patients with acute STsegment elevation myocardial infarction(STEMI).METHODS Sixty patients with first STEMI undergoing direct percutaneous coronary intervention from February 2008 to October 2008 were randomly assigned to an exercise group(n=30)and a control group(n=30).The levels of MMP-9 and TIMP-1 were measured in all patients at 1 d,10-14 d,30 d,and 6 mo after admission.Two-dimensional echocardiography and cardiopulmonary exercise testing were done in patients at 10-14 d and 6 mo after admission.RESULTS There was no significant difference in CPET at baseline between the exercise group and the control group.At 6 mo,the time of exercise,peak and anaerobic threshold values of O2 uptake,and metabolic equivalents increased in both groups,but markedly increased in the exercise group.At baseline,there were no significant differences in left ventricular ejection fraction(LVEF)between the two groups.At 6 mo,LVEF increased in the exercise group,but not in the control group.At 6 mo,the percentage of patients with positive result of LVRM was 26.6%in the exercise group and 52.6%in the control group(P<0.05).The levels of plasma MMP-9 and TIMP-1 and the ratio of MMP-9 to TIMP-1 in both groups had no significant difference at 1 d and 10-14 d after AMI,but at 30 d and 6 mo,the levels of plasma MMP-9 and TIMP-1 in the exercise group were significantly lower than those in the control group;the ratio of MMP-9 to TIMP-1 in the exercise group was significantly higher than that in the control group.CONCLUSION ET under supervision based on home condition in early and recovery stage of AMI can improve exercise cardiopulmonary function and prevent the LVRM.Therefore,it may reduce unfavorable remodeling response by decreasing the levels of plasma MMP-9 and TIMP-1 and adjusting the ratio of MMP-9 to TIMP-1 hereafter.展开更多
Organic solvent nanofiltration(OSN)membranes have a great application prospect in organic solvent separation,but the development of OSN membranes is mainly restricted by trade-off between permeability and rejection ra...Organic solvent nanofiltration(OSN)membranes have a great application prospect in organic solvent separation,but the development of OSN membranes is mainly restricted by trade-off between permeability and rejection rate.In this work,a TA/Fe^(3+)polymer was introduced into polyetherimide(PEI)ultrafiltration membranes crosslinked with hexamethylene diamine as the intermediate layer,and OSN membranes with high separation performance and solvent permeability were obtained through interfacial polymerization and solvent activation.The interlayer with high surface hydrophilicity and a fixed pore structure controlled the adsorption/diffusion of the amine monomer during interfacial polymerization,forming a smooth(average surface roughness<5.5 nm),ultra-thin(separation layer thickness reduced from 150 to 16 nm)and dense surface structure polyamide(PA)layer.The PA-Fe^(3+)_3-HDA/PEI membrane retained more than 94%of methyl blue(BS)in 0.1 g·L^(-1)BS ethanol solution at 0.6 MPa,and the ethanol permeation reached 28.56 L^(-1)·m^(-2)·h^(-1).The average flux recovery ratio(FRR)of PA-Fe^(3+)_(3)-HDA/PEI membrane was found to be 84%,which has better fouling resistance than PA-HDA/PEI membrane,and it was found to have better stability performance through different solvent immersion experiments and continuous operation in 0.1 g·L^(-1)BS ethanol solution.Compared with thin-film composite nanofiltration membranes,the PA-Fe^(3+)_(3)-HDA/PEI membrane can be manufactured from an economical and environment-friendly method and overcomes the trade-off between permeability and rejection rate,showing great application potential in organic solvent separation systems.展开更多
Quasi-one-dimensional NiO with a hierarchically porous structure was synthesized through a facile coordination−precipitation method with the coupling effect of ammonia and a post-calcination treatment.The electrocatal...Quasi-one-dimensional NiO with a hierarchically porous structure was synthesized through a facile coordination−precipitation method with the coupling effect of ammonia and a post-calcination treatment.The electrocatalytic properties of NiO fibers for the oxidation of ethanol were compared with those of NiO spheres.The results show that the fibrous NiO possesses a larger specific surface area of 140.153 m2/g and a lower electrical resistivity of 4.5×105Ω·m,leading to an impressively superior electrocatalytic activity to spherical NiO for ethanol oxidation in alkaline media.The current decay on fibrous NiO at 0.6 V in 100−900 s was 0.00003%,which is much lower than that of spherical NiO,indicating its better stability.The unique morphology and hierarchically porous structure give the fibrous NiO great potential to be used as an anodic electrocatalyst for direct ethanol fuel cells.展开更多
The shortest path is a widely studied network science problem and has attracted great attention.Nevertheless,it draws little attention in temporal networks,in which temporal edges determine information dissemination.I...The shortest path is a widely studied network science problem and has attracted great attention.Nevertheless,it draws little attention in temporal networks,in which temporal edges determine information dissemination.In this paper,we propose an information spreading-based method to calculate the shortest paths distribution in temporal networks.We verify our method on both artificial and real-world temporal networks and obtain a good agreement.We further generalize our method to identify influential nodes and found an effective method.Finally,we verify the influential nodes identifying method on four networks.展开更多
基金supported by 111 Project (No.D21025)Open Fund Project of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Nos.PLN2021-01,PLN2021-02,PLN2021-03)+2 种基金High-end Foreign Expert Introduction Program (No.G2021036005L)National Key Research and Development Program (No.2021YFC2800903)National Natural Science Foundation of China (No.U20B6005-05)。
文摘During the operational process of natural gas gathering and transmission pipelines,the formation of hydrates is highly probable,leading to uncontrolled movement and aggregation of hydrates.The continuous migration and accumulation of hydrates further contribute to the obstruction of natural gas pipelines,resulting in production reduction,shutdowns,and pressure build-ups.Consequently,a cascade of risks is prone to occur.To address this issue,this study focuses on the operational process of natural gas gathering and transmission pipelines,where a comprehensive framework is established.This framework includes theoretical models for pipeline temperature distribution,pipeline pressure distribution,multiphase flow within the pipeline,hydrate blockage,and numerical solution methods.By analyzing the influence of inlet temperature,inlet pressure,and terminal pressure on hydrate formation within the pipeline,the sensitivity patterns of hydrate blockage risks are derived.The research indicates that reducing inlet pressure and terminal pressure could lead to a decreased maximum hydrate formation rate,potentially mitigating pipeline blockage during natural gas transportation.Furthermore,an increase in inlet temperature and terminal pressure,and a decrease in inlet pressure,results in a displacement of the most probable location for hydrate blockage towards the terminal station.However,it is crucial to note that operating under low-pressure conditions significantly elevates energy consumption within the gathering system,contradicting the operational goal of energy efficiency and reduction of energy consumption.Consequently,for high-pressure gathering pipelines,measures such as raising the inlet temperature or employing inhibitors,electrical heat tracing,and thermal insulation should be adopted to prevent hydrate formation during natural gas transportation.Moreover,considering abnormal conditions such as gas well production and pipeline network shutdowns,which could potentially trigger hydrate formation,the installation of methanol injection connectors remains necessary to ensure production safety.
基金the supports of project funded by China Postdoctoral Science Foundation(2023M743886)Project of Shale Gas Evaluation and Exploitation Key Laboratory of Sichuan Province(YSK2023004)youth project funded by Shaanxi Province Natural Science Basic Research Program(2024JC-YBQN-0522)。
文摘The casing deformation prevention technology based on the optimization of cement slurry is proposed to reduce the casing deformation of shale oil and gas wells during hydraulic fracturing. In this paper, the fracture mechanism of hollow particles in cement sheath was firstly analyzed by discrete element method, and the effect of hollow particles in cement on casing deformation was investigated by laboratory experiment method. Finally, field test was carried out to verify the improvement effect of the casing deformation based on cement slurry modification. The results show that the formation displacement can be absorbed effectively by hollow particles inside the cement transferring the excessive deformation away from casing. The particles in the uncemented state provide deformation space during formation slipping. The casing with diameter of 139.7 mm could be passed through by bridge plug with the diameter of 99 mm when the mass ratio of particle/cement reaches 1:4. According to the field test feedback, the method based on optimization of cement slurry can effectively reduce the risk of casing deformation, and the recommended range of hollow microbeads content in the cement slurry is between 15% and 25%.
基金This work were supported by the Beijing Municipal Administration of Hospitals Clinical Medicine Development of Special Funding Support （No. ZYLX201303）, the National Natural Science Foundation of China （No. 81470429, No.81270285）, and The capital health research and development of special （No 2011-2006-14）.
文摘Coronary artery calcification （CAC） is highly prevalent in patients with coronary heart disease （CHD） and is associated with major adverse cardiovascular events. There are two recognized type of CAC--intimal and medial calcification, and each of them have specific risk factors. Several theories about the mechanism of vascular calcification have been put forward, and we currently believe that vascular calcification is an active, regulated process. CAC can usually be found in patients with severe CHD, and this asymptomatic phenomenon make early diagnosis of CAC important. Coronary computed tomographic angiography is the main noninvasive tool to detect calcified lesions. Measurement of coronary artery calcification by scoring is a reasonable metric for cardiovascular risk assessment in asymptomatic adults at intermediate risk. To date, effective medical treatment of CAC has not been identified. Several strategies of percutaneous coronary interven- tion have been applied to CHD patients with CAC, but with unsatisfactory results. Prognosis of CAC is still a major problem of CHD pa- tients. Thus, more details about the mechanisms of CAC need to be elucidated in order to improve the understanding and treatment of CAC.
基金supported by National Natural Science Foundation of China(Grant No.60535020)National Natural Science Funds for Distinguished Young Scholars of China(Grant No.60525314)
文摘Gecko-like robot（Geckobot）,an important branch of bionic robotics,is a robot that simulates gecko＇s capacity to climb walls and ceilings.The work environment of the traditional wall-climbing robot is greatly limited as the moving structure and adsorption principle of the robot have nothing to do with the real gecko.However,the adsorption principle and moving mode of the real gecko can provide a new way to break through the restrictions of the traditional wall-climbing robot.Inspired by the moving mechanism of geckos, this paper develops the Geckobot with motile body.Two types of Geckobots are addressed：one with compliant flat bar as the body,and the other with prismatic joint as the body.The compliant body not only resembles the moving mode of the real gecko body,but also simplifies the Geckobot＇s structure.The prismatic joint body is used to adapt the change of body length in ground-to-wall transition. The gait planning on the plane and the transition between perpendicular intersectional planes is discussed,with an emphasis on the analysis of the kinematics degree of freedom（DOF） and body posture.Central pattern generator（CPG） neural network is realized in LabVIEW and utilized to control Geckobot＇s movement.The CPG scheme in Lab VIEW is given,and how CPG is used to control Geckobot to turn or move forward is explored.Simulations are conducted in ADAMS to verify the feasibility of the structure design and gait planning and to acquire some parameters for practical Geckobot development.The experiment with Geckobot-Ⅰand Geckobot-Ⅱon their crawling capacity on the plane and the ground-to-wall transition finds that the robot can complete the crawling movement and ground-to-wall transition,verifying the feasibility of the structure design,gait planning and the CPG motion control.The Geckobot structure design approach,gait planning and the CPG motion control presented would be useful for the research on wall-climbing robots.
基金Supported by Beijing Hospitals Authority Incubating Program,No.PZ2021007Beijing Hospitals Authority Youth Program,No.QML20200604Beijing Municipal Health Commission(No.17-3)and the Beijing Natural Science Foundation,No.7184205.
文摘BACKGROUND A growing amount of evidence provides support for the hypothesis that acute myocardial infarction(AMI)patients should go through cardiopulmonary exercise testing(CPET)about 3-5 d after AMI is diagnosed,make reasonable exercising prescription,and conduct exercise training under guidance.AIM To investigate the effect of exercise training(ET)on left ventricular systolic function and left ventricular remodeling(LVRM)and to study the possible mechanisms of LVRM by the changes of matrix metallopeptidase 9(MMP-9)and tissue inhibitor of metalloproteinases 1(TIMP-1)in patients with acute STsegment elevation myocardial infarction(STEMI).METHODS Sixty patients with first STEMI undergoing direct percutaneous coronary intervention from February 2008 to October 2008 were randomly assigned to an exercise group(n=30)and a control group(n=30).The levels of MMP-9 and TIMP-1 were measured in all patients at 1 d,10-14 d,30 d,and 6 mo after admission.Two-dimensional echocardiography and cardiopulmonary exercise testing were done in patients at 10-14 d and 6 mo after admission.RESULTS There was no significant difference in CPET at baseline between the exercise group and the control group.At 6 mo,the time of exercise,peak and anaerobic threshold values of O2 uptake,and metabolic equivalents increased in both groups,but markedly increased in the exercise group.At baseline,there were no significant differences in left ventricular ejection fraction(LVEF)between the two groups.At 6 mo,LVEF increased in the exercise group,but not in the control group.At 6 mo,the percentage of patients with positive result of LVRM was 26.6%in the exercise group and 52.6%in the control group(P<0.05).The levels of plasma MMP-9 and TIMP-1 and the ratio of MMP-9 to TIMP-1 in both groups had no significant difference at 1 d and 10-14 d after AMI,but at 30 d and 6 mo,the levels of plasma MMP-9 and TIMP-1 in the exercise group were significantly lower than those in the control group;the ratio of MMP-9 to TIMP-1 in the exercise group was significantly higher than that in the control group.CONCLUSION ET under supervision based on home condition in early and recovery stage of AMI can improve exercise cardiopulmonary function and prevent the LVRM.Therefore,it may reduce unfavorable remodeling response by decreasing the levels of plasma MMP-9 and TIMP-1 and adjusting the ratio of MMP-9 to TIMP-1 hereafter.
基金supported by grants from the National Natural Science Foundation of China (41662004)the Jiangxi Graduate Innovation Fund (YC2021-S557),China。
文摘Organic solvent nanofiltration(OSN)membranes have a great application prospect in organic solvent separation,but the development of OSN membranes is mainly restricted by trade-off between permeability and rejection rate.In this work,a TA/Fe^(3+)polymer was introduced into polyetherimide(PEI)ultrafiltration membranes crosslinked with hexamethylene diamine as the intermediate layer,and OSN membranes with high separation performance and solvent permeability were obtained through interfacial polymerization and solvent activation.The interlayer with high surface hydrophilicity and a fixed pore structure controlled the adsorption/diffusion of the amine monomer during interfacial polymerization,forming a smooth(average surface roughness<5.5 nm),ultra-thin(separation layer thickness reduced from 150 to 16 nm)and dense surface structure polyamide(PA)layer.The PA-Fe^(3+)_3-HDA/PEI membrane retained more than 94%of methyl blue(BS)in 0.1 g·L^(-1)BS ethanol solution at 0.6 MPa,and the ethanol permeation reached 28.56 L^(-1)·m^(-2)·h^(-1).The average flux recovery ratio(FRR)of PA-Fe^(3+)_(3)-HDA/PEI membrane was found to be 84%,which has better fouling resistance than PA-HDA/PEI membrane,and it was found to have better stability performance through different solvent immersion experiments and continuous operation in 0.1 g·L^(-1)BS ethanol solution.Compared with thin-film composite nanofiltration membranes,the PA-Fe^(3+)_(3)-HDA/PEI membrane can be manufactured from an economical and environment-friendly method and overcomes the trade-off between permeability and rejection rate,showing great application potential in organic solvent separation systems.
基金Project(51404306)supported by the National Natural Science Foundation of ChinaProject(JNJJ201613)supported by Jiana Foundation of Central South University,ChinaProject(2017YFC0210401)supported by the National Key Research and Development Program of China。
文摘Quasi-one-dimensional NiO with a hierarchically porous structure was synthesized through a facile coordination−precipitation method with the coupling effect of ammonia and a post-calcination treatment.The electrocatalytic properties of NiO fibers for the oxidation of ethanol were compared with those of NiO spheres.The results show that the fibrous NiO possesses a larger specific surface area of 140.153 m2/g and a lower electrical resistivity of 4.5×105Ω·m,leading to an impressively superior electrocatalytic activity to spherical NiO for ethanol oxidation in alkaline media.The current decay on fibrous NiO at 0.6 V in 100−900 s was 0.00003%,which is much lower than that of spherical NiO,indicating its better stability.The unique morphology and hierarchically porous structure give the fibrous NiO great potential to be used as an anodic electrocatalyst for direct ethanol fuel cells.
基金Project supported by the National Natural Science Foundation of China(Grant No.61903266)China Postdoctoral Science Foundation(Grant No.2018M631073)+2 种基金China Postdoctoral Science Special Foundation(Grant No.2019T120829)the Fundamental Research Funds for the Central Universities,ChinaSichuan Science and Technology Program,China(Grant No.20YYJC4001)。
文摘The shortest path is a widely studied network science problem and has attracted great attention.Nevertheless,it draws little attention in temporal networks,in which temporal edges determine information dissemination.In this paper,we propose an information spreading-based method to calculate the shortest paths distribution in temporal networks.We verify our method on both artificial and real-world temporal networks and obtain a good agreement.We further generalize our method to identify influential nodes and found an effective method.Finally,we verify the influential nodes identifying method on four networks.
