Given the challenge of definitively discriminating between chemical and nuclear explosions using seismic methods alone,surface detection of signature noble gas radioisotopes is considered a positive identification of ...Given the challenge of definitively discriminating between chemical and nuclear explosions using seismic methods alone,surface detection of signature noble gas radioisotopes is considered a positive identification of underground nuclear explosions(UNEs).However,the migration of signature radionuclide gases between the nuclear cavity and surface is not well understood because complex processes are involved,including the generation of complex fracture networks,reactivation of natural fractures and faults,and thermo-hydro-mechanical-chemical(THMC)coupling of radionuclide gas transport in the subsurface.In this study,we provide an experimental investigation of hydro-mechanical(HM)coupling among gas flow,stress states,rock deformation,and rock damage using a unique multi-physics triaxial direct shear rock testing system.The testing system also features redundant gas pressure and flow rate measurements,well suited for parameter uncertainty quantification.Using porous tuff and tight granite samples that are relevant to historic UNE tests,we measured the Biot effective stress coefficient,rock matrix gas permeability,and fracture gas permeability at a range of pore pressure and stress conditions.The Biot effective stress coefficient varies from 0.69 to 1 for the tuff,whose porosity averages 35.3%±0.7%,while this coefficient varies from 0.51 to 0.78 for the tight granite(porosity<1%,perhaps an underestimate).Matrix gas permeability is strongly correlated to effective stress for the granite,but not for the porous tuff.Our experiments reveal the following key engineering implications on transport of radionuclide gases post a UNE event:(1)The porous tuff shows apparent fracture dilation or compression upon stress changes,which does not necessarily change the gas permeability;(2)The granite fracture permeability shows strong stress sensitivity and is positively related to shear displacement;and(3)Hydromechanical coupling among stress states,rock damage,and gas flow appears to be stronger in tight granite than in porous tuff.展开更多
Debonding at the cement-casing interface is recognized as a principal failure mechanism leading to CO_(2) leakage in wells.This detachment gives rise to a microannulus,which notably possesses greater permeability than...Debonding at the cement-casing interface is recognized as a principal failure mechanism leading to CO_(2) leakage in wells.This detachment gives rise to a microannulus,which notably possesses greater permeability than undamaged cement,undermining its sealing efficacy.Conventionally,the permeability of the microannulus is regarded as a uniform value throughout the well.However,fundamentally,a microannulus is one type of fracture,and its gap or aperture size is affected by the effective stress.In this work,we developed a unique experimental apparatus.This equipment facilitates the curing of cement inside a steel casing,the formation of a microannulus between the casing and the cement,and the investigation of the fluid flow dynamics along the microannulus under laboratory-replicated in situ conditions.The microannulus was formed by injecting fluid from one end of the setup,and receiving similar amount of fluid on the other end signified the development of the leakage channel.Additionally,strain gauges affixed to the casing’s external surface yielded key information on the microannulus’s opening and closure.We observed a noticeable decline in microannulus hydraulic aperture(or permeability)in relation to effective stress and an exponential equation fits their relationship.Our findings also indicate a distinct behavior when comparing liquid CO_(2) with water.Specifically,it is easier for liquid CO_(2) to create the microannulus.However,the hydraulic aperture range for this microannulus(0.7-6 mm)is considerably smaller than that created by water flow(2-17 mm).Finally,we integrated the stressdependent microannulus aperture size into the combined analysis of well mechanical integrity and well leakage.The outcomes consistently demonstrated that when factoring in the stress-dependent aperture sizes,the leakage rates are 3e5 times compared to a fixed aperture model.The traditional assumption of a constant aperture significantly underestimates fluid leakage risks.展开更多
[目的/意义]系统审视并分析国外冲突性健康信息研究的现状、热点以及前沿,以全面把握该领域的发展情况,为未来研究提供有益的参考和支持。[方法/过程]在Web of Science和Elsevier ScienceDirect两个外文数据库中检索冲突性健康信息的研...[目的/意义]系统审视并分析国外冲突性健康信息研究的现状、热点以及前沿,以全面把握该领域的发展情况,为未来研究提供有益的参考和支持。[方法/过程]在Web of Science和Elsevier ScienceDirect两个外文数据库中检索冲突性健康信息的研究文献,利用VOSviewer可视化工具分析文献的发文趋势以及研究热点和前沿,并对这些分析结果进行详细的阐释和说明。[结果/结论]国外冲突性健康信息研究正处于高速发展阶段,研究热点包括:冲突性健康信息产生原因和来源研究、冲突性健康信息对公众健康认知和行为的影响研究、冲突性健康信息下的公众健康决策研究以及冲突性健康信息应对和治理研究。研究前沿涵盖了不确定性视角下的冲突性健康信息、冲突性健康信息的延滞效应以及跨学科理论的冲突性健康信息研究。展开更多
Lower Earth Orbit(LEO) satellite becomes an important part of complementing terrestrial communication due to its lower orbital altitude and smaller propagation delay than Geostationary satellite. However, the LEO sate...Lower Earth Orbit(LEO) satellite becomes an important part of complementing terrestrial communication due to its lower orbital altitude and smaller propagation delay than Geostationary satellite. However, the LEO satellite communication system cannot meet the requirements of users when the satellite-terrestrial link is blocked by obstacles. To solve this problem, we introduce Intelligent reflect surface(IRS) for improving the achievable rate of terrestrial users in LEO satellite communication. We investigated joint IRS scheduling, user scheduling, power and bandwidth allocation(JIRPB) optimization algorithm for improving LEO satellite system throughput.The optimization problem of joint user scheduling and resource allocation is formulated as a non-convex optimization problem. To cope with this problem, the nonconvex optimization problem is divided into resource allocation optimization sub-problem and scheduling optimization sub-problem firstly. Second, we optimize the resource allocation sub-problem via alternating direction multiplier method(ADMM) and scheduling sub-problem via Lagrangian dual method repeatedly.Third, we prove that the proposed resource allocation algorithm based ADMM approaches sublinear convergence theoretically. Finally, we demonstrate that the proposed JIRPB optimization algorithm improves the LEO satellite communication system throughput.展开更多
为揭示大叶茶(Camellia sinensis var.assamica,CSA)研究的热点及前沿,研究采用文献计量学的方法,利用SCI-E和SSCI数据库进行检索,从发文趋势、研究力量布局、研究主题及演变规律、前沿发展态势探测方面进行分析。结果显示:关于大叶茶...为揭示大叶茶(Camellia sinensis var.assamica,CSA)研究的热点及前沿,研究采用文献计量学的方法,利用SCI-E和SSCI数据库进行检索,从发文趋势、研究力量布局、研究主题及演变规律、前沿发展态势探测方面进行分析。结果显示:关于大叶茶的研究总发文量呈上升趋势,分为萌芽期(1976-2004年)、发展期(2005-2014年)和快速增长期(2015年至今)3个阶段;发文单位以安徽农业大学、中国科学院和云南农业大学为主,刊载相关研究论文最多的期刊为《Journal of Agricultural and Food Chemistry》;关键词分析中,Antioxidant(抗氧化)、Theacrine(苦茶碱)和Fermentation(发酵)等具有较高词频,Genome(基因组)和Metabolomics(代谢组学)兼具高频词和新兴词的特征,为研究的热点词汇;引文网络分析显示,全基因组遗传分析、茶树系统发生学研究、靶向/非靶向代谢组分析以及化合物差异化分析为研究前沿。研究结果为学者开展研究以及相关机构制定科技战略规划提供参考。展开更多
基金supported by the Laboratory Directed Research&Development(LDRD)program at the Los Alamos National Laboratory(LANL)(Grant No.20220019DR).
文摘Given the challenge of definitively discriminating between chemical and nuclear explosions using seismic methods alone,surface detection of signature noble gas radioisotopes is considered a positive identification of underground nuclear explosions(UNEs).However,the migration of signature radionuclide gases between the nuclear cavity and surface is not well understood because complex processes are involved,including the generation of complex fracture networks,reactivation of natural fractures and faults,and thermo-hydro-mechanical-chemical(THMC)coupling of radionuclide gas transport in the subsurface.In this study,we provide an experimental investigation of hydro-mechanical(HM)coupling among gas flow,stress states,rock deformation,and rock damage using a unique multi-physics triaxial direct shear rock testing system.The testing system also features redundant gas pressure and flow rate measurements,well suited for parameter uncertainty quantification.Using porous tuff and tight granite samples that are relevant to historic UNE tests,we measured the Biot effective stress coefficient,rock matrix gas permeability,and fracture gas permeability at a range of pore pressure and stress conditions.The Biot effective stress coefficient varies from 0.69 to 1 for the tuff,whose porosity averages 35.3%±0.7%,while this coefficient varies from 0.51 to 0.78 for the tight granite(porosity<1%,perhaps an underestimate).Matrix gas permeability is strongly correlated to effective stress for the granite,but not for the porous tuff.Our experiments reveal the following key engineering implications on transport of radionuclide gases post a UNE event:(1)The porous tuff shows apparent fracture dilation or compression upon stress changes,which does not necessarily change the gas permeability;(2)The granite fracture permeability shows strong stress sensitivity and is positively related to shear displacement;and(3)Hydromechanical coupling among stress states,rock damage,and gas flow appears to be stronger in tight granite than in porous tuff.
基金Financial support for this work from the U.S.Department of Energy(DOE)Office of Basic Energy Sciences for“Center for Coupled Chemo-Mechanics of Cementitious Composites for EGS(C4M)”,DOE’s“National Risk Assessment Partnership(NRAP)”programDOE Office of Energy Efficiency&Renewable Energy’s Geothermal Technologies Office for“Advanced Downhole Acoustic Sensing for Wellbore Integrity”is gratefully acknowledged.
文摘Debonding at the cement-casing interface is recognized as a principal failure mechanism leading to CO_(2) leakage in wells.This detachment gives rise to a microannulus,which notably possesses greater permeability than undamaged cement,undermining its sealing efficacy.Conventionally,the permeability of the microannulus is regarded as a uniform value throughout the well.However,fundamentally,a microannulus is one type of fracture,and its gap or aperture size is affected by the effective stress.In this work,we developed a unique experimental apparatus.This equipment facilitates the curing of cement inside a steel casing,the formation of a microannulus between the casing and the cement,and the investigation of the fluid flow dynamics along the microannulus under laboratory-replicated in situ conditions.The microannulus was formed by injecting fluid from one end of the setup,and receiving similar amount of fluid on the other end signified the development of the leakage channel.Additionally,strain gauges affixed to the casing’s external surface yielded key information on the microannulus’s opening and closure.We observed a noticeable decline in microannulus hydraulic aperture(or permeability)in relation to effective stress and an exponential equation fits their relationship.Our findings also indicate a distinct behavior when comparing liquid CO_(2) with water.Specifically,it is easier for liquid CO_(2) to create the microannulus.However,the hydraulic aperture range for this microannulus(0.7-6 mm)is considerably smaller than that created by water flow(2-17 mm).Finally,we integrated the stressdependent microannulus aperture size into the combined analysis of well mechanical integrity and well leakage.The outcomes consistently demonstrated that when factoring in the stress-dependent aperture sizes,the leakage rates are 3e5 times compared to a fixed aperture model.The traditional assumption of a constant aperture significantly underestimates fluid leakage risks.
文摘[目的/意义]系统审视并分析国外冲突性健康信息研究的现状、热点以及前沿,以全面把握该领域的发展情况,为未来研究提供有益的参考和支持。[方法/过程]在Web of Science和Elsevier ScienceDirect两个外文数据库中检索冲突性健康信息的研究文献,利用VOSviewer可视化工具分析文献的发文趋势以及研究热点和前沿,并对这些分析结果进行详细的阐释和说明。[结果/结论]国外冲突性健康信息研究正处于高速发展阶段,研究热点包括:冲突性健康信息产生原因和来源研究、冲突性健康信息对公众健康认知和行为的影响研究、冲突性健康信息下的公众健康决策研究以及冲突性健康信息应对和治理研究。研究前沿涵盖了不确定性视角下的冲突性健康信息、冲突性健康信息的延滞效应以及跨学科理论的冲突性健康信息研究。
基金supported by the National Key R&D Program of China under Grant 2020YFB1807900the National Natural Science Foundation of China (NSFC) under Grant 61931005Beijing University of Posts and Telecommunications-China Mobile Research Institute Joint Innovation Center。
文摘Lower Earth Orbit(LEO) satellite becomes an important part of complementing terrestrial communication due to its lower orbital altitude and smaller propagation delay than Geostationary satellite. However, the LEO satellite communication system cannot meet the requirements of users when the satellite-terrestrial link is blocked by obstacles. To solve this problem, we introduce Intelligent reflect surface(IRS) for improving the achievable rate of terrestrial users in LEO satellite communication. We investigated joint IRS scheduling, user scheduling, power and bandwidth allocation(JIRPB) optimization algorithm for improving LEO satellite system throughput.The optimization problem of joint user scheduling and resource allocation is formulated as a non-convex optimization problem. To cope with this problem, the nonconvex optimization problem is divided into resource allocation optimization sub-problem and scheduling optimization sub-problem firstly. Second, we optimize the resource allocation sub-problem via alternating direction multiplier method(ADMM) and scheduling sub-problem via Lagrangian dual method repeatedly.Third, we prove that the proposed resource allocation algorithm based ADMM approaches sublinear convergence theoretically. Finally, we demonstrate that the proposed JIRPB optimization algorithm improves the LEO satellite communication system throughput.
文摘为揭示大叶茶(Camellia sinensis var.assamica,CSA)研究的热点及前沿,研究采用文献计量学的方法,利用SCI-E和SSCI数据库进行检索,从发文趋势、研究力量布局、研究主题及演变规律、前沿发展态势探测方面进行分析。结果显示:关于大叶茶的研究总发文量呈上升趋势,分为萌芽期(1976-2004年)、发展期(2005-2014年)和快速增长期(2015年至今)3个阶段;发文单位以安徽农业大学、中国科学院和云南农业大学为主,刊载相关研究论文最多的期刊为《Journal of Agricultural and Food Chemistry》;关键词分析中,Antioxidant(抗氧化)、Theacrine(苦茶碱)和Fermentation(发酵)等具有较高词频,Genome(基因组)和Metabolomics(代谢组学)兼具高频词和新兴词的特征,为研究的热点词汇;引文网络分析显示,全基因组遗传分析、茶树系统发生学研究、靶向/非靶向代谢组分析以及化合物差异化分析为研究前沿。研究结果为学者开展研究以及相关机构制定科技战略规划提供参考。
