Polymer nanocomposites have been investigated for about three decades. To get deep insights into the modifying effects of various nanofillers on mechanical and physical properties of polymer nanocomposites, the three ...Polymer nanocomposites have been investigated for about three decades. To get deep insights into the modifying effects of various nanofillers on mechanical and physical properties of polymer nanocomposites, the three basic aspects of processing, characterization and properties are critically reviewed in this paper. Nanofillers can be classified into three major types of two-dimensional (2D) layered, one-dimensional (1D) fibrous and zerodimensional (0D) spherical ones and this review thus discusses in detail the processing, characterization and properties of the three types of polymer nanocomposites. It starts with an introduction of various nanoscale fillers such as two-dimensional (2D) nano-clay, graphene and MXene, one dimensional (1D) carbon nanofibers and nanotubes, zero dimensional (0D) silica nanoparticles and ZnO quantum dots as well as nanofiller-polymer interfaces. The processing of these polymer nanocomposites using different methods and the characterization of nanofillers and polymer nanocomposites using various techniques are described. Finally, the mechanical and physical properties of these polymer nanocomposites are discussed by considering the effects of nanofiller type, dispersion and contents;also, interface properties show significant effects on the mechanical properties of polymer nanocomposites and are discussed in some details.展开更多
In this work,a flowing material balance equation(FMBE) is established for under saturated coalbed methane(CBM) reservoirs,which considers immobile free gas expansion effect at the dewatering stage.Based on the establi...In this work,a flowing material balance equation(FMBE) is established for under saturated coalbed methane(CBM) reservoirs,which considers immobile free gas expansion effect at the dewatering stage.Based on the established FMBE,five straight-line methods are proposed to determine the control area,initial water reserve,initial free gas reserve,initial adsorbed gas reserve,original gas in place,as well as permeability at the same time.Subsequently,the proposed FMBE methods for undersaturated CBM reservoirs are validated against a reservoir simulation software with and without considering free gas expansion.Finally,the proposed methods are applied in a field case when considering free gas expansion effect.Validation cases show that the straight-line relationships for the proposed five FMBE methods are excellent,and good agreements are obtained among the actual reserves and permeabilities and those evaluated by the proposed five FMBE methods,indicating the proposed five FMBE methods are effective and rational for CBM reservoirs.Results show that a small amount of free gas will result in a great deviation in reserve evaluation;hence,the immobile free gas expansion effect should be considered when establishing the material balance equation of undersaturated CBM reservoirs at the dewatering stage.展开更多
BACKGROUND Remote ischemic conditioning(RIC)is used to protect against myocardial injury.However,there is no adequate evidence for comprehensive RIC in elderly patients with ST-segment elevation myocardial infarction(...BACKGROUND Remote ischemic conditioning(RIC)is used to protect against myocardial injury.However,there is no adequate evidence for comprehensive RIC in elderly patients with ST-segment elevation myocardial infarction(STEMI).This study aimed to test whether comprehensive RIC,started pre-primary percutaneous coronary intervention(PPCI)and repeated daily on 1-30 days post-PPCI,can improve myocardial salvage index(SI),left ventricular ejection fraction(LVEF),Kansas City Cardiomyopathy Questionnaire Clinical Summary Score(KCCQ-CSS)and 6-min walk test distance(6MWD)in elderly patients with acute STEMI during 12 months follow-up.METHODS 328 consenting elderly patients were randomized to receive standard PPCI plus comprehensive RIC(the treatment group)or standard PPCI(the control group).SI at 5-7 days after PPCI,LVEF,left ventricular end-diastolic volume index(LVEDVI),left ventricular end-systolic volume index(LVESVI),KCCQ-CSS,6MWD and adverse events rates were measured and assessed.RESULTS SI was significantly higher in the treatment group[interquartile range(IQR):0.38-0.66,P=0.037].There were no significant differences in major adverse events at 12 months.Although the differences of LVEDVI,LVESVI and LVEF between the treatment group and the control group did not reach statistical significance at 6 months and 12 months,LVEF tended to be higher,LVEDVI tended to be lower in the treatment group.The KCCQ-CSS was significantly higher in the treatment group at 1 month(IQR:46.5-87,P=0.001)and 12 months(IQR:55-93,P=0.008).There was significant difference in 6MWD between the treatment group and the control group(IQR:258-360 vs.IQR:250-345,P=0.002)at 1 month and(IQR:360-445 vs.IQR:345-432,P=0.035)at 12 months.A modest correlation was found between SI and LVEF(r=0.452,P<0.01),KCCQ-CSS(r=0.440,P<0.01)and 6MWD(r=0.384,P<0.01)respectively at 12 months.CONCLUSIONS The comprehensive RIC can improve SI,KCCQ-CSS and 6MWD.It may be an adjunctive therapy to PPCI in elderly patients with STEMI.展开更多
Path planning is a key technique of autonomous navigation for robots,and the velocity field is an important part.Constructing velocity field in a complex workspace is still challenging.In this paper,an inner normal gu...Path planning is a key technique of autonomous navigation for robots,and the velocity field is an important part.Constructing velocity field in a complex workspace is still challenging.In this paper,an inner normal guided segmentation algorithm in a complex polygon is proposed to decompose the complex workspace in this paper.The artificial potential field model based on probability theory is then used to calculate the potential field of the decomposed workspace,and the velocity field is obtained by utilizing the potential field of this workspace.Path optimization is implemented by curve evolution,during which the internal force generated in the smoothing process of the initial path by a mean filter and the external force is obtained from the gradient of the workspace potential field.The parameter selection principle is deduced by analyzing the influence of several parameters on the path length and smoothness.Simulation results show that the designed polygon decomposition algorithm can effectively segment complex workspace and that the path optimization algorithm can shorten and smoothen paths.展开更多
Advanced machine learning(ML)approaches such as transfer learning have seldom been applied to approximate quantum many-body systems.Here we demonstrate that a simple recurrent unit(SRU)based efficient and transferable...Advanced machine learning(ML)approaches such as transfer learning have seldom been applied to approximate quantum many-body systems.Here we demonstrate that a simple recurrent unit(SRU)based efficient and transferable sequence learning framework is capable of learning and accurately predicting the time evolution of the one-dimensional(ID)Ising model with simultaneous transverse and parallel magnetic fields,as quantitatively corroborated by relative entropy measurements between the predicted and exact state distributions.At a cost of constant computational complexity,a larger many-body state evolution is predicted in an autoregressive way from just one initial state,without any guidance or knowledge of any Hamiltonian.Our work paves the way for future applications of advanced ML methods in quantum many-body dynamics with knowledge only from a smaller system.展开更多
基金National Natural Science Foundation of China (Nos. 51573200, 11872132 and U183720015) for financial support
文摘Polymer nanocomposites have been investigated for about three decades. To get deep insights into the modifying effects of various nanofillers on mechanical and physical properties of polymer nanocomposites, the three basic aspects of processing, characterization and properties are critically reviewed in this paper. Nanofillers can be classified into three major types of two-dimensional (2D) layered, one-dimensional (1D) fibrous and zerodimensional (0D) spherical ones and this review thus discusses in detail the processing, characterization and properties of the three types of polymer nanocomposites. It starts with an introduction of various nanoscale fillers such as two-dimensional (2D) nano-clay, graphene and MXene, one dimensional (1D) carbon nanofibers and nanotubes, zero dimensional (0D) silica nanoparticles and ZnO quantum dots as well as nanofiller-polymer interfaces. The processing of these polymer nanocomposites using different methods and the characterization of nanofillers and polymer nanocomposites using various techniques are described. Finally, the mechanical and physical properties of these polymer nanocomposites are discussed by considering the effects of nanofiller type, dispersion and contents;also, interface properties show significant effects on the mechanical properties of polymer nanocomposites and are discussed in some details.
基金supported by the National Science and Technology Major Projects of China (No. 2016ZX05042 and No. 2017ZX05039)the National Natural Science Foundation Projects of China (No. 51504269 and No. 51490654)Science Foundation of China University of Petroleum, Beijing (No.C201605) to support part of this work。
文摘In this work,a flowing material balance equation(FMBE) is established for under saturated coalbed methane(CBM) reservoirs,which considers immobile free gas expansion effect at the dewatering stage.Based on the established FMBE,five straight-line methods are proposed to determine the control area,initial water reserve,initial free gas reserve,initial adsorbed gas reserve,original gas in place,as well as permeability at the same time.Subsequently,the proposed FMBE methods for undersaturated CBM reservoirs are validated against a reservoir simulation software with and without considering free gas expansion.Finally,the proposed methods are applied in a field case when considering free gas expansion effect.Validation cases show that the straight-line relationships for the proposed five FMBE methods are excellent,and good agreements are obtained among the actual reserves and permeabilities and those evaluated by the proposed five FMBE methods,indicating the proposed five FMBE methods are effective and rational for CBM reservoirs.Results show that a small amount of free gas will result in a great deviation in reserve evaluation;hence,the immobile free gas expansion effect should be considered when establishing the material balance equation of undersaturated CBM reservoirs at the dewatering stage.
基金supported by the National Natural Science Foundation of China(No.62172288)the Beijing Municipal Science&Technology Commission(Z151100003915095).
文摘BACKGROUND Remote ischemic conditioning(RIC)is used to protect against myocardial injury.However,there is no adequate evidence for comprehensive RIC in elderly patients with ST-segment elevation myocardial infarction(STEMI).This study aimed to test whether comprehensive RIC,started pre-primary percutaneous coronary intervention(PPCI)and repeated daily on 1-30 days post-PPCI,can improve myocardial salvage index(SI),left ventricular ejection fraction(LVEF),Kansas City Cardiomyopathy Questionnaire Clinical Summary Score(KCCQ-CSS)and 6-min walk test distance(6MWD)in elderly patients with acute STEMI during 12 months follow-up.METHODS 328 consenting elderly patients were randomized to receive standard PPCI plus comprehensive RIC(the treatment group)or standard PPCI(the control group).SI at 5-7 days after PPCI,LVEF,left ventricular end-diastolic volume index(LVEDVI),left ventricular end-systolic volume index(LVESVI),KCCQ-CSS,6MWD and adverse events rates were measured and assessed.RESULTS SI was significantly higher in the treatment group[interquartile range(IQR):0.38-0.66,P=0.037].There were no significant differences in major adverse events at 12 months.Although the differences of LVEDVI,LVESVI and LVEF between the treatment group and the control group did not reach statistical significance at 6 months and 12 months,LVEF tended to be higher,LVEDVI tended to be lower in the treatment group.The KCCQ-CSS was significantly higher in the treatment group at 1 month(IQR:46.5-87,P=0.001)and 12 months(IQR:55-93,P=0.008).There was significant difference in 6MWD between the treatment group and the control group(IQR:258-360 vs.IQR:250-345,P=0.002)at 1 month and(IQR:360-445 vs.IQR:345-432,P=0.035)at 12 months.A modest correlation was found between SI and LVEF(r=0.452,P<0.01),KCCQ-CSS(r=0.440,P<0.01)and 6MWD(r=0.384,P<0.01)respectively at 12 months.CONCLUSIONS The comprehensive RIC can improve SI,KCCQ-CSS and 6MWD.It may be an adjunctive therapy to PPCI in elderly patients with STEMI.
基金supported by the financial support of the ship segmentation intelligent manufacturing equipment solution and key common technology research,High-tech Ship Research Project of the Chinese Ministry of Science and Technology and the project of Shandong Provincial Key R&D Program(No.2019GGX104035).
文摘Path planning is a key technique of autonomous navigation for robots,and the velocity field is an important part.Constructing velocity field in a complex workspace is still challenging.In this paper,an inner normal guided segmentation algorithm in a complex polygon is proposed to decompose the complex workspace in this paper.The artificial potential field model based on probability theory is then used to calculate the potential field of the decomposed workspace,and the velocity field is obtained by utilizing the potential field of this workspace.Path optimization is implemented by curve evolution,during which the internal force generated in the smoothing process of the initial path by a mean filter and the external force is obtained from the gradient of the workspace potential field.The parameter selection principle is deduced by analyzing the influence of several parameters on the path length and smoothness.Simulation results show that the designed polygon decomposition algorithm can effectively segment complex workspace and that the path optimization algorithm can shorten and smoothen paths.
基金the National Natural Science Foundation of China under Grant Nos 11874431 and 11804181the National Key R&D Program of China under Grant No 2018YFA0306800+1 种基金the Guangdong Science and Technology Innovation Youth Talent Program under Grant Nos 2016TQ03X688 and 2018YFA0306504the Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics under Grant No ZZ201803.
文摘Advanced machine learning(ML)approaches such as transfer learning have seldom been applied to approximate quantum many-body systems.Here we demonstrate that a simple recurrent unit(SRU)based efficient and transferable sequence learning framework is capable of learning and accurately predicting the time evolution of the one-dimensional(ID)Ising model with simultaneous transverse and parallel magnetic fields,as quantitatively corroborated by relative entropy measurements between the predicted and exact state distributions.At a cost of constant computational complexity,a larger many-body state evolution is predicted in an autoregressive way from just one initial state,without any guidance or knowledge of any Hamiltonian.Our work paves the way for future applications of advanced ML methods in quantum many-body dynamics with knowledge only from a smaller system.
