The Ordovician-Silurian transition was marked by extensive volcanic activity globally.In South China,intensive volcanism was documented by abundant ash layers in strata,but the origins and tectonic settings of these a...The Ordovician-Silurian transition was marked by extensive volcanic activity globally.In South China,intensive volcanism was documented by abundant ash layers in strata,but the origins and tectonic settings of these ashes remain controversial.This study presents the stratigraphic distribution of volcanic ash layers,zircon trace element and Hf isotope data from the Wanhe Section in the southwestern Yangtze Shelf,providing insights into the tectonic setting and the origin of the parent magmas.The results suggest that volcanic ashes in the southwestern Yangtze Shelf primarily originated from arc magmatism in the Wuyi-Yunkai Orogen,with a mixed source from mantle and crust.The findings corroborate the hypothesis that the Late Ordovician–Silurian Wuyi-Yunkai Orogen in South China represents a collisional orogenic belt.展开更多
Policy training against diverse opponents remains a challenge when using Multi-Agent Reinforcement Learning(MARL)in multiple Unmanned Combat Aerial Vehicle(UCAV)air combat scenarios.In view of this,this paper proposes...Policy training against diverse opponents remains a challenge when using Multi-Agent Reinforcement Learning(MARL)in multiple Unmanned Combat Aerial Vehicle(UCAV)air combat scenarios.In view of this,this paper proposes a novel Dominant and Non-dominant strategy sample selection(DoNot)mechanism and a Local Observation Enhanced Multi-Agent Proximal Policy Optimization(LOE-MAPPO)algorithm to train the multi-UCAV air combat policy and improve its generalization.Specifically,the LOE-MAPPO algorithm adopts a mixed state that concatenates the global state and individual agent's local observation to enable efficient value function learning in multi-UCAV air combat.The DoNot mechanism classifies opponents into dominant or non-dominant strategy opponents,and samples from easier to more challenging opponents to form an adaptive training curriculum.Empirical results demonstrate that the proposed LOE-MAPPO algorithm outperforms baseline MARL algorithms in multi-UCAV air combat scenarios,and the DoNot mechanism leads to stronger policy generalization when facing diverse opponents.The results pave the way for the fast generation of cooperative strategies for air combat agents with MARLalgorithms.展开更多
The commercial exploitation of unconventional petroleum resources(e.g.,shale oil/gas and tight oil/gas)has drastically changed the global energy structure within the past two decades.Sweet-spot intervals(areas),the mo...The commercial exploitation of unconventional petroleum resources(e.g.,shale oil/gas and tight oil/gas)has drastically changed the global energy structure within the past two decades.Sweet-spot intervals(areas),the most prolific unconventional hydrocarbon resources,generally consist of extraordinarily high organic matter(EHOM)deposits or closely associated sandstones/carbonate rocks.The formation of sweet-spot intervals(areas)is fundamentally controlled by their depositional and subsequent diagenetic settings,which result from the coupled sedimentation of global or regional geological events,such as tectonic activity,sea level(lake level)fluctuations,climate change,bottom water anoxia,volcanic activity,biotic mass extinction or radiation,and gravity flows during a certain geological period.Black shales with EHOM content and their associated high-quality reservoir rocks deposited by the coupling of major geological events provide not only a prerequisite for massive hydrocarbon generation but also abundant hydrocarbon storage space.The Ordovician-Silurian Wufeng-Longmaxi shale of the Sichuan Basin,Devonian Marcellus shale of the Appalachian Basin,Devonian-Carboniferous Bakken Formation of the Williston Basin,and Triassic Yanchang Formation of the Ordos Basin are four typical unconventional hydrocarbon systems selected as case studies herein.In each case,the formation of sweet-spot intervals for unconventional hydrocarbon resources was controlled by the coupled sedimentation of different global or regional geological events,collectively resulting in a favorable environment for the production,preservation,and accumulation of organic matter,as well as for the generation,migration,accumulation,and exploitation of hydrocarbons.Unconventional petroleum sedimentology,which focuses on coupled sedimentation during dramatic environmental changes driven by major geological events,is key to improve the understanding of the formation and distribution of sweet-spot intervals(areas)in unconventional petroleum systems.展开更多
Coronavirus Disease 2019(COVID-19),caused by a novel coronavirus(SARS-Co V-2),is a highly contagious disease.It firstly appeared in Wuhan,Hubei province of China in December 2019.During the next two months,it moved ra...Coronavirus Disease 2019(COVID-19),caused by a novel coronavirus(SARS-Co V-2),is a highly contagious disease.It firstly appeared in Wuhan,Hubei province of China in December 2019.During the next two months,it moved rapidly throughout China.Most of the infected patients have mild symptoms including fever,fatigue and cough,but in severe cases,patients can progress rapidly and develop into acute respiratory distress syndrome,septic shock,metabolic acidosis and coagulopathy.The new coronavirus was reported to spread via droplets,contact and natural aerosols from human to human.Therefore,aerosol-producing procedures such as endotracheal intubation may put the anesthesiologists at high risk of nosocomial infections.In fact,SARSCo V-2 infection of anesthesiologists after endotracheal intubation for confirmed COVID-19 patients have been reported in hospitals in Wuhan.The expert panel of airway management in Chinese Society of Anaesthesiology has deliberated and drafted this recommendation,by which we hope to guide the performance of endotracheal intubation by frontline anesthesiologists and critical care physicians.During the airway management,enhanced droplet/airborne personal protective equitment(PPE)should be applied to the health care providers.A good airway assessment before airway intervention is of vital importance.For patients with normal airway,awake intubation should be avoided,and modified rapid sequence induction is strongly recommended.Sufficient muscle relaxant should be assured before intubation.For patients with difficult airway,good preparation of airway devices and detailed intubation plans should be made.展开更多
Coal correlation cannot only guide coal and coalbed methane exploitation,but may also provide valuable information for the evolution of the paleoclimate and paleoenvironment during coalaccumulation periods.It is diffi...Coal correlation cannot only guide coal and coalbed methane exploitation,but may also provide valuable information for the evolution of the paleoclimate and paleoenvironment during coalaccumulation periods.It is difficult to undertake coal correlation in a terrestrial basin due to multiple superimposed coal seams and a lack of effective marker beds.In this study,based on the analyses of coal-bearing sedimentary environments and the observations of field outcrops and drilling cores,three key sequence surfaces of the Middle Jurassic Xishanyao Formation were identified in the middle part of the southern Junggar Basin.Three third-order sequences(S.Ⅲ1,S.Ⅲ2 and S.Ⅲ3)and ten fourth-order sequences were divided within the Xishanyao Formation.Regional coal correlation was finally identified,combined with the layered vertical pattern coal and its interval thickness,coal maceral,and coal quality data.In terms of the coal correlation within a specific sequence set,the interval of the B2–B3 coals was approximately three times thicker than that of the B3–B5 coals,which was the main marker for regional coal correlation in the Lower Xishanyao Formation.Furthermore,the phenomena of steadily developed B4 coal seam(2–3 m in thickness)across the Liuhuanggou coal mining area(eastern study region)and the large-small-large variation for intervals between the B8 and B9,B9 and B10,and B10 and B11 coal seams in the Manasi coal mining(western study region)were also an effective means for local coal correlation.Increasing vitrinite and sulphur content and decreasing inertinite content in a third-order sequence were found,which were likely to be closely related to lake level fluctuations.Based on the variation of coal macerals,the wildfire frequency gradually decreased from the bottom to the top of the Xishanyao Formation.The predicted O2level of the S.Ⅲ1,S.Ⅲ2,and S.Ⅲ3 of the Xishanyao Formation was 26.36%,24.22%,and 22.51%,respectively.Except for global paleoclimate effects,the provenance direction changes caused by the Bogda Mountains uplifts would result in a regular variation of coal maceral and coal quality across the study region.展开更多
In order to meet the higher accuracy requirement of trajectory prediction for Unmanned Aircraft System(UAS)in Unmanned Aircraft System Traffic Management(UTM),an Intent Based Trajectory Prediction and Smooth Based on ...In order to meet the higher accuracy requirement of trajectory prediction for Unmanned Aircraft System(UAS)in Unmanned Aircraft System Traffic Management(UTM),an Intent Based Trajectory Prediction and Smooth Based on Constrained State-dependent-transition Hybrid Estimation(CSDTHE-IBTPS)algorithm is proposed.Firstly,an intent inference method of UAS is constructed based on the information of ADS-B and geofence system.Moreover,a geofence layering algorithm is proposed.Secondly,the Flight Mode Change Points(FMCP)are used to define the relevant mode transition parameters and design the guard conditions,so as to generate the mode transition probability matrix and establish the continuous state-dependent-transition model.After that,the constrained Kalman filter(CKF)is applied to improve State-dependent-transition Hybrid Estimation(SDTHE)algorithm by applying equality constraint to the velocity of UAS in the straight phase and turning phase,respectively,and thus the constrained state-dependent-transition hybrid estimation(CSDTHE)algorithm is constructed.Finally,the results of intent inference and hybrid estimation are used to make trajectory prediction.Furthermore,each flight segment of trajectory is smoothed respectively by Rauch-Tung-Striebel(RTS)backward smooth method using the proposed CSDTHE-RTS algorithm,so as to obtain more accurate trajectory prediction results.The simulation shows that the proposed algorithm can reduce the errors of trajectory prediction and the time delay of intent inference.展开更多
Eukaryotic genomes are hierarchically packaged into cell nucleus,affecting gene regulation.The genome is organized into multiscale structural units,including chromosome territories,compartments,topologically associati...Eukaryotic genomes are hierarchically packaged into cell nucleus,affecting gene regulation.The genome is organized into multiscale structural units,including chromosome territories,compartments,topologically associating domains(TADs),and DNA loops.The identification of these hierarchical structures has benefited from the development of experimental approaches,such as 3C-based methods(Hi-C,ChIA-PET,etc.),imaging tools(2D-FISH,3D-FISH,Cryo-FISH,etc.)and ligation-free methods(GAM,SPRITE,etc.).In recent two decades,numerous studies have shown that the 3D organization of genome plays essential roles in multiple cellular processes via various mechanisms,such as regulating enhancer activity and promoter-enhancer interactions.However,there are relatively few studies about the 3D genome in livestock species.Therefore,studies for exploring the function of 3D genomes in livestock are urgently needed to provide a more comprehensive understanding of potential relationships between the genome and production traits.In this review,we summarize the recent advances of 3D genomics and its biological functions in human and mouse studies,drawing inspiration to explore the 3D genomics of livestock species.We then mainly focus on the biological functions of 3D genome organization in muscle development and its implications in animal breeding.展开更多
Consensus control of multi-agent systems has attracted compelling attentions from various scientific communities for its promising applications.This paper presents a discrete-time consensus protocol for a class of mul...Consensus control of multi-agent systems has attracted compelling attentions from various scientific communities for its promising applications.This paper presents a discrete-time consensus protocol for a class of multi-agent systems with switching topologies and input constraints based on distributed predictive control scheme.The consensus protocol is not only distributed but also depends on the errors of states between agent and its neighbors.We focus mainly on dealing with the input constraints and a distributed model predictive control scheme is developed to achieve stable consensus under the condition that both velocity and acceleration constraints are included simultaneously.The acceleration constraint is regarded as the changing rate of velocity based on some reasonable assumptions so as to simplify the analysis.Theoretical analysis shows that the constrained system steered by the proposed protocol achieves consensus asymptotically if the switching interaction graphs always have a spanning tree.Numerical examples are also provided to illustrate the validity of the algorithm.展开更多
The pore structures of coal can directly affect the adsorption and seepage capacity of coalbed methane(CBM),which therefore is an important influence on CBM exploration and development.In this study,the pore structure...The pore structures of coal can directly affect the adsorption and seepage capacity of coalbed methane(CBM),which therefore is an important influence on CBM exploration and development.In this study,the pore structures of low-rank coals from the Middle Jurassic Xishanyao Formation in the southern Junggar Basin were analyzed,and the fractal dimensions(D1,D2,D3 and D4 corresponding to pore sizes of 0-5 nm,5-100 nm,100-1000 nm and 1000-20000 nm,respectively)were calculated to quantitatively describe these coal pore structures.The results show that Xishanyao coal is characterized by open pore morphology,good pore connectivity and well-developed seepage pores and microfractures,which is beneficial to CBM seepage.The D1 and D2 can be used to characterize the pore surface and structure of adsorption pores respectively.The D3 and D4 can be used to represent the pore structure of seepage pores.Compared with adsorption pores,the structure of seepage pores is more affected by the change of coal rank.The D1 is better than D2 in characterizing the methane adsorption capacity.When D1>2.2,D1 is positively correlated with Langmuir volume(VL)and negatively correlated with Langmuir pressure(PL),while D2 shows a weak opposite trend.The coals with the higher D1 and lower D2 are associated with a higher VL,indicating the coal reservoir with more complex pore surfaces and simpler pore structures has stronger methane adsorption capacity.D4 is better than D3 in characterizing the methane seepage capacity.The porosity and permeability of coal reservoirs increase with the increase of D4,while D3 displays an opposite trend,which is mainly related to the well-developed microfractures.The well-developed fracture system enhances the seepage capacity of the Xishanyao coal reservoir.This study reveals the fractal characteristics of pore structure and its significant influence on adsorption and seepage capacity of low-rank coal.展开更多
This paper presents a rule-based framework for addressing decision-making problems within the context of the "UI-STRIVE"Competition.First,two distinct autonomous confrontation scenarios are described:autonom...This paper presents a rule-based framework for addressing decision-making problems within the context of the "UI-STRIVE"Competition.First,two distinct autonomous confrontation scenarios are described:autonomous air combat and cooperative interception.Second,a State-Event-Condition-Action(SECA)decision-making framework is developed,which integrates thefinite state machine and event-condition-action frameworks.This framework provides three products to describe rules,i.e.the SECA model,the SECA state chart,and the SECA rule description.Third,the situation assessment and target assignment during autonomous air combat are investigated,and the mathematical models are established.Finally,the decisionmaking model's rationality and feasibility are verified through data simulation and analysis.展开更多
基金funded by the National Natural Science Foundation of China(Nos.42222209 and 42488201)the State Scholarship Fund.
文摘The Ordovician-Silurian transition was marked by extensive volcanic activity globally.In South China,intensive volcanism was documented by abundant ash layers in strata,but the origins and tectonic settings of these ashes remain controversial.This study presents the stratigraphic distribution of volcanic ash layers,zircon trace element and Hf isotope data from the Wanhe Section in the southwestern Yangtze Shelf,providing insights into the tectonic setting and the origin of the parent magmas.The results suggest that volcanic ashes in the southwestern Yangtze Shelf primarily originated from arc magmatism in the Wuyi-Yunkai Orogen,with a mixed source from mantle and crust.The findings corroborate the hypothesis that the Late Ordovician–Silurian Wuyi-Yunkai Orogen in South China represents a collisional orogenic belt.
文摘Policy training against diverse opponents remains a challenge when using Multi-Agent Reinforcement Learning(MARL)in multiple Unmanned Combat Aerial Vehicle(UCAV)air combat scenarios.In view of this,this paper proposes a novel Dominant and Non-dominant strategy sample selection(DoNot)mechanism and a Local Observation Enhanced Multi-Agent Proximal Policy Optimization(LOE-MAPPO)algorithm to train the multi-UCAV air combat policy and improve its generalization.Specifically,the LOE-MAPPO algorithm adopts a mixed state that concatenates the global state and individual agent's local observation to enable efficient value function learning in multi-UCAV air combat.The DoNot mechanism classifies opponents into dominant or non-dominant strategy opponents,and samples from easier to more challenging opponents to form an adaptive training curriculum.Empirical results demonstrate that the proposed LOE-MAPPO algorithm outperforms baseline MARL algorithms in multi-UCAV air combat scenarios,and the DoNot mechanism leads to stronger policy generalization when facing diverse opponents.The results pave the way for the fast generation of cooperative strategies for air combat agents with MARLalgorithms.
基金jointly supported by the Scientific Research and Technological Development Programs of CNPC(2021yjcq02 and 2021DJ2001)。
文摘The commercial exploitation of unconventional petroleum resources(e.g.,shale oil/gas and tight oil/gas)has drastically changed the global energy structure within the past two decades.Sweet-spot intervals(areas),the most prolific unconventional hydrocarbon resources,generally consist of extraordinarily high organic matter(EHOM)deposits or closely associated sandstones/carbonate rocks.The formation of sweet-spot intervals(areas)is fundamentally controlled by their depositional and subsequent diagenetic settings,which result from the coupled sedimentation of global or regional geological events,such as tectonic activity,sea level(lake level)fluctuations,climate change,bottom water anoxia,volcanic activity,biotic mass extinction or radiation,and gravity flows during a certain geological period.Black shales with EHOM content and their associated high-quality reservoir rocks deposited by the coupling of major geological events provide not only a prerequisite for massive hydrocarbon generation but also abundant hydrocarbon storage space.The Ordovician-Silurian Wufeng-Longmaxi shale of the Sichuan Basin,Devonian Marcellus shale of the Appalachian Basin,Devonian-Carboniferous Bakken Formation of the Williston Basin,and Triassic Yanchang Formation of the Ordos Basin are four typical unconventional hydrocarbon systems selected as case studies herein.In each case,the formation of sweet-spot intervals for unconventional hydrocarbon resources was controlled by the coupled sedimentation of different global or regional geological events,collectively resulting in a favorable environment for the production,preservation,and accumulation of organic matter,as well as for the generation,migration,accumulation,and exploitation of hydrocarbons.Unconventional petroleum sedimentology,which focuses on coupled sedimentation during dramatic environmental changes driven by major geological events,is key to improve the understanding of the formation and distribution of sweet-spot intervals(areas)in unconventional petroleum systems.
文摘Coronavirus Disease 2019(COVID-19),caused by a novel coronavirus(SARS-Co V-2),is a highly contagious disease.It firstly appeared in Wuhan,Hubei province of China in December 2019.During the next two months,it moved rapidly throughout China.Most of the infected patients have mild symptoms including fever,fatigue and cough,but in severe cases,patients can progress rapidly and develop into acute respiratory distress syndrome,septic shock,metabolic acidosis and coagulopathy.The new coronavirus was reported to spread via droplets,contact and natural aerosols from human to human.Therefore,aerosol-producing procedures such as endotracheal intubation may put the anesthesiologists at high risk of nosocomial infections.In fact,SARSCo V-2 infection of anesthesiologists after endotracheal intubation for confirmed COVID-19 patients have been reported in hospitals in Wuhan.The expert panel of airway management in Chinese Society of Anaesthesiology has deliberated and drafted this recommendation,by which we hope to guide the performance of endotracheal intubation by frontline anesthesiologists and critical care physicians.During the airway management,enhanced droplet/airborne personal protective equitment(PPE)should be applied to the health care providers.A good airway assessment before airway intervention is of vital importance.For patients with normal airway,awake intubation should be avoided,and modified rapid sequence induction is strongly recommended.Sufficient muscle relaxant should be assured before intubation.For patients with difficult airway,good preparation of airway devices and detailed intubation plans should be made.
基金supported by the National Science and Technology Major Project(No.2016ZX05041004-003)the China Geological Survey Scientific Research Project(No.DD20160204)+1 种基金the Guiding Program of Liaoning Natural Science Founds(No.2019-ZD-0046)the Scientific Research Funding Project of Liaoning Education Department(No.LJ2019JL004)。
文摘Coal correlation cannot only guide coal and coalbed methane exploitation,but may also provide valuable information for the evolution of the paleoclimate and paleoenvironment during coalaccumulation periods.It is difficult to undertake coal correlation in a terrestrial basin due to multiple superimposed coal seams and a lack of effective marker beds.In this study,based on the analyses of coal-bearing sedimentary environments and the observations of field outcrops and drilling cores,three key sequence surfaces of the Middle Jurassic Xishanyao Formation were identified in the middle part of the southern Junggar Basin.Three third-order sequences(S.Ⅲ1,S.Ⅲ2 and S.Ⅲ3)and ten fourth-order sequences were divided within the Xishanyao Formation.Regional coal correlation was finally identified,combined with the layered vertical pattern coal and its interval thickness,coal maceral,and coal quality data.In terms of the coal correlation within a specific sequence set,the interval of the B2–B3 coals was approximately three times thicker than that of the B3–B5 coals,which was the main marker for regional coal correlation in the Lower Xishanyao Formation.Furthermore,the phenomena of steadily developed B4 coal seam(2–3 m in thickness)across the Liuhuanggou coal mining area(eastern study region)and the large-small-large variation for intervals between the B8 and B9,B9 and B10,and B10 and B11 coal seams in the Manasi coal mining(western study region)were also an effective means for local coal correlation.Increasing vitrinite and sulphur content and decreasing inertinite content in a third-order sequence were found,which were likely to be closely related to lake level fluctuations.Based on the variation of coal macerals,the wildfire frequency gradually decreased from the bottom to the top of the Xishanyao Formation.The predicted O2level of the S.Ⅲ1,S.Ⅲ2,and S.Ⅲ3 of the Xishanyao Formation was 26.36%,24.22%,and 22.51%,respectively.Except for global paleoclimate effects,the provenance direction changes caused by the Bogda Mountains uplifts would result in a regular variation of coal maceral and coal quality across the study region.
基金This work was financially supported by the Major Program of National Natural Science Foundation of Chinathe National Natural Science Foundation of China[Grant No.61703427].
文摘In order to meet the higher accuracy requirement of trajectory prediction for Unmanned Aircraft System(UAS)in Unmanned Aircraft System Traffic Management(UTM),an Intent Based Trajectory Prediction and Smooth Based on Constrained State-dependent-transition Hybrid Estimation(CSDTHE-IBTPS)algorithm is proposed.Firstly,an intent inference method of UAS is constructed based on the information of ADS-B and geofence system.Moreover,a geofence layering algorithm is proposed.Secondly,the Flight Mode Change Points(FMCP)are used to define the relevant mode transition parameters and design the guard conditions,so as to generate the mode transition probability matrix and establish the continuous state-dependent-transition model.After that,the constrained Kalman filter(CKF)is applied to improve State-dependent-transition Hybrid Estimation(SDTHE)algorithm by applying equality constraint to the velocity of UAS in the straight phase and turning phase,respectively,and thus the constrained state-dependent-transition hybrid estimation(CSDTHE)algorithm is constructed.Finally,the results of intent inference and hybrid estimation are used to make trajectory prediction.Furthermore,each flight segment of trajectory is smoothed respectively by Rauch-Tung-Striebel(RTS)backward smooth method using the proposed CSDTHE-RTS algorithm,so as to obtain more accurate trajectory prediction results.The simulation shows that the proposed algorithm can reduce the errors of trajectory prediction and the time delay of intent inference.
基金supported by the National Natural Science Foundation of China(31972558)the Agricultural Improved Seed Project of Shandong Province,China(2020LZGC014)。
文摘Eukaryotic genomes are hierarchically packaged into cell nucleus,affecting gene regulation.The genome is organized into multiscale structural units,including chromosome territories,compartments,topologically associating domains(TADs),and DNA loops.The identification of these hierarchical structures has benefited from the development of experimental approaches,such as 3C-based methods(Hi-C,ChIA-PET,etc.),imaging tools(2D-FISH,3D-FISH,Cryo-FISH,etc.)and ligation-free methods(GAM,SPRITE,etc.).In recent two decades,numerous studies have shown that the 3D organization of genome plays essential roles in multiple cellular processes via various mechanisms,such as regulating enhancer activity and promoter-enhancer interactions.However,there are relatively few studies about the 3D genome in livestock species.Therefore,studies for exploring the function of 3D genomes in livestock are urgently needed to provide a more comprehensive understanding of potential relationships between the genome and production traits.In this review,we summarize the recent advances of 3D genomics and its biological functions in human and mouse studies,drawing inspiration to explore the 3D genomics of livestock species.We then mainly focus on the biological functions of 3D genome organization in muscle development and its implications in animal breeding.
基金This work was financially supported by the Major Program of National Natural Science Foundation of China[grant numbers is not public]the National Natural Science Foundation of China[Grant No.61703427].
文摘Consensus control of multi-agent systems has attracted compelling attentions from various scientific communities for its promising applications.This paper presents a discrete-time consensus protocol for a class of multi-agent systems with switching topologies and input constraints based on distributed predictive control scheme.The consensus protocol is not only distributed but also depends on the errors of states between agent and its neighbors.We focus mainly on dealing with the input constraints and a distributed model predictive control scheme is developed to achieve stable consensus under the condition that both velocity and acceleration constraints are included simultaneously.The acceleration constraint is regarded as the changing rate of velocity based on some reasonable assumptions so as to simplify the analysis.Theoretical analysis shows that the constrained system steered by the proposed protocol achieves consensus asymptotically if the switching interaction graphs always have a spanning tree.Numerical examples are also provided to illustrate the validity of the algorithm.
文摘The pore structures of coal can directly affect the adsorption and seepage capacity of coalbed methane(CBM),which therefore is an important influence on CBM exploration and development.In this study,the pore structures of low-rank coals from the Middle Jurassic Xishanyao Formation in the southern Junggar Basin were analyzed,and the fractal dimensions(D1,D2,D3 and D4 corresponding to pore sizes of 0-5 nm,5-100 nm,100-1000 nm and 1000-20000 nm,respectively)were calculated to quantitatively describe these coal pore structures.The results show that Xishanyao coal is characterized by open pore morphology,good pore connectivity and well-developed seepage pores and microfractures,which is beneficial to CBM seepage.The D1 and D2 can be used to characterize the pore surface and structure of adsorption pores respectively.The D3 and D4 can be used to represent the pore structure of seepage pores.Compared with adsorption pores,the structure of seepage pores is more affected by the change of coal rank.The D1 is better than D2 in characterizing the methane adsorption capacity.When D1>2.2,D1 is positively correlated with Langmuir volume(VL)and negatively correlated with Langmuir pressure(PL),while D2 shows a weak opposite trend.The coals with the higher D1 and lower D2 are associated with a higher VL,indicating the coal reservoir with more complex pore surfaces and simpler pore structures has stronger methane adsorption capacity.D4 is better than D3 in characterizing the methane seepage capacity.The porosity and permeability of coal reservoirs increase with the increase of D4,while D3 displays an opposite trend,which is mainly related to the well-developed microfractures.The well-developed fracture system enhances the seepage capacity of the Xishanyao coal reservoir.This study reveals the fractal characteristics of pore structure and its significant influence on adsorption and seepage capacity of low-rank coal.
文摘This paper presents a rule-based framework for addressing decision-making problems within the context of the "UI-STRIVE"Competition.First,two distinct autonomous confrontation scenarios are described:autonomous air combat and cooperative interception.Second,a State-Event-Condition-Action(SECA)decision-making framework is developed,which integrates thefinite state machine and event-condition-action frameworks.This framework provides three products to describe rules,i.e.the SECA model,the SECA state chart,and the SECA rule description.Third,the situation assessment and target assignment during autonomous air combat are investigated,and the mathematical models are established.Finally,the decisionmaking model's rationality and feasibility are verified through data simulation and analysis.
