Since launched in March 2002,the Gravity Recovery and Climate Experiment(GRACE)satellite gravity mission has brought a new era to the studies of large-scale mass transport and redistribution within different component...Since launched in March 2002,the Gravity Recovery and Climate Experiment(GRACE)satellite gravity mission has brought a new era to the studies of large-scale mass transport and redistribution within different components of the Earth system,including the atmosphere,hydrosphere,ocean,cryosphere,and solid Earth,and greatly improved our understanding of the Earth climate system and solid Earth geophysics.This paper provides a comprehensive review of GRACE satellite gravimetry and its geophysical applications in monitoring and quantifying water mass changes in various components of the global water cycle,ice mass balance of polar ice sheets and mountain glaciers,global sea level change,and mass redistribution in solid Earth.We also discuss in detail different GRACE data products(e.g.,standard spherical harmonic and mascon solutions),commonly used GRACE data post-processing methods,major challenges in using different GRACE data and how to correctly address those challenges.展开更多
The Gravity Recovery and Climate Experiment(GRACE) has been measuring temporal and spatial variations of mass redistribution within the Earth system since2002. As large earthquakes cause significant mass changes on ...The Gravity Recovery and Climate Experiment(GRACE) has been measuring temporal and spatial variations of mass redistribution within the Earth system since2002. As large earthquakes cause significant mass changes on and under the Earth's surface,GRACE provides a new means from space to observe mass redistribution due to earthquake deformations. GRACE serves as a good complement to other earthquake measurements because of its extensive spatial coverage and being free from terrestrial restriction. During its over 10 years mission,GRACE has successfully detected seismic gravitational changes of several giant earthquakes,which include the 2004 Sumatra–Andaman earthquake,2010 Maule(Chile) earthquake,and 2011 Tohoku-Oki(Japan) earthquake. In this review,we describe by examples how to process GRACE timevariable gravity data to retrieve seismic signals,and summarize the results of recent studies that apply GRACE observations to detect co- and post-seismic signals and constrain fault slip models and viscous lithospheric structures. We also discuss major problems and give an outlook in this field of GRACE application.展开更多
Using more than 14 years of GRACE(Gravity Recovery and Climate Experiment) satellite gravimetry observations, we estimate the ice loss rate for the Patagonia Ice Field(PIF) of South America. After correcting the effec...Using more than 14 years of GRACE(Gravity Recovery and Climate Experiment) satellite gravimetry observations, we estimate the ice loss rate for the Patagonia Ice Field(PIF) of South America. After correcting the effects of glacier isostatic adjustment(GIA) and hydrological variations, the ice loss rate is -23.5 ± 8.1 Giga ton per year(Gt/yr) during the period April 2002 through December 2016, equivalent to an average ice thickness change of-1.3 m/yr if evenly distributed over PIF. The PIF ice mass change series also show obvious inter-annual variations during the entire period. For the time spans April 2002 to December 2007, January 2008 to December 2012 and January 2013 to December 2016, the ice loss rates are -26.4,-9.0 and -25.0 Gt/yr, respectively, indicating that the ice melting experienced significant slowing down and accelerating again in the past decade. Comparison with time series from temperature and precipitation data over PIF suggests that the inter-annual ice losses might not be directly correlated with the temperature changes and precipitation anomalies, and thus their interrelation is intricate. However, the dramatic ice loss acceleration in 2016(with more than 100 Gt within the first half of the year) appears closely related with the evident temperature increase and severe precipitation shortage over 2016, which are likely correlated with the strong E1 Nino event around 2016. Moreover, we compare the GRACE spherical harmonic(SH) and mass concentration(Mascon) solutions in estimating the PIF ice loss rate, and find that the Mascon result has larger uncertainty in leakage error correction,while the SH solutions can better correct leakage errors based on a constrained forward modeling iterative method. Thus the GRACE SH solutions with constrained forward modeling recovery are recommended to evaluating the ice mass change of PIF or other glacier regions with relatively smaller spatial scales.展开更多
The observed Earth’s polar motion on decadal time scales has long been conjectured to be excited by the exchange of equatorial angular momentum between the solid mantle and the fluid outer core,via the mechanism of e...The observed Earth’s polar motion on decadal time scales has long been conjectured to be excited by the exchange of equatorial angular momentum between the solid mantle and the fluid outer core,via the mechanism of electromagnetic(EM)core-mantle coupling.However,past estimations of the EM coupling torque from surface geomagnetic observations is too weak to account for the observed decadal polar motion.Our recent estimations from numerical geodynamo simulations have shown the opposite.In this paper,we re-examine in detail the EM coupling mechanism and the properties of the magnetic field in the electrically conducting lower mantle(characterized by a thin D '-layer at the base of the mantle).Our simulations find that the toroidal field in the D'-layer from the induction and convection of the toroidal field in the outer core could be potentially much stronger than that from the advection of the poloidal field in the outer core.The former,however,cannot be inferred from geomagnetic observations at the Earth’s surface,and is missing in previous EM torque estimated from geomagnetic observations.Our deduction suggests further that this field could make the actual EM coupling torque sufficiently strong,at approximately 5×1019 Nm,to excite,and hence explain,the decadal polar motion to magnitude of approximately 10 mas.展开更多
Indoor environment has significant impacts on human health as people spend 90%of their time indoors.The COVID-19 pandemic and the increased public health awareness have further elevated the urgency for cultivating and...Indoor environment has significant impacts on human health as people spend 90%of their time indoors.The COVID-19 pandemic and the increased public health awareness have further elevated the urgency for cultivating and maintaining a healthy indoor environment.The advancement in emerging digital twin technologies including building information modeling(BIM),Internet of Things(IoT),data analytics,and smart control have led to new opportunities for building design and operation.Despite the numerous studies on developing methods for creating digital twins and enabling new functionalities and services in smart building management,very few have focused on the health of indoor environment.There is a critical need for understanding and envisaging how digital twin paradigms can be geared towards healthy indoor environment.Therefore,this study reviews the techniques for developing digital twins and discusses how the techniques can be customized to contribute to public health.Specifically,the current applications of BIM,IoT sensing,data analytics,and smart building control technologies for building digital twins are reviewed,and the knowledge gaps and limitations are discussed to guide future research for improving environmental and occupant health.Moreover,this paper elaborates a vision for future research on integrated digital twins for a healthy indoor environment with special considerations of the above four emerging techniques and issues.This review contributes to the body of knowledge by advocating for the consideration of health in digital twin modeling and smart building services and presenting the research roadmap for digital twin-enabled healthy indoor environment.展开更多
A series of AIN nanostructures were synthesized by an ultrahigh-temperature, catalyst-free, physical vapor transport(PVT) process. Energy dispersive X-ray spectroscopy(EDX), X-ray diffraction(XRD), X-Ray photoel...A series of AIN nanostructures were synthesized by an ultrahigh-temperature, catalyst-free, physical vapor transport(PVT) process. Energy dispersive X-ray spectroscopy(EDX), X-ray diffraction(XRD), X-Ray photoelectron spectroscopy(XPS),high resolution transmission electron microscopy(HRTEM) detection show that high quality AIN nanowires were prepared. Nanostructures including nanorings, nanosprings, nanohelices, chainlike nanowires, six-fold symmetric nanostructure and rod-like structure were successfully obtained by controlling the growth duration and temperature. The morphology evolution was attributed to electrostatic polar charge model and the crystalline lattice structure of AIN.展开更多
The Laowan deposit is a large gold deposit in the Qinling-Dabie orogenic belt where pyrite is the main Au-bearing mineral phase.We present results from the occurrences of gold,trace elements and sulfur isotopes of pyr...The Laowan deposit is a large gold deposit in the Qinling-Dabie orogenic belt where pyrite is the main Au-bearing mineral phase.We present results from the occurrences of gold,trace elements and sulfur isotopes of pyrite,and hydrogen and oxygen isotopes of quartz and calcite to elucidate the sources of ore-forming fluid;the genesis of pyrite and the ore-forming process.From field observations,five generations of pyrite are identified;one formed in a metamorphic-diagenetic epoch(PyI),and the others during four mineralization stages:1)the coarse-grained pyrite-quartz stage(PyII),2)the quartz and medium-to fine-grained pyrite stage(PyIII),3)the polymetallic sulfide stage(PyIV),and 4)the carbonate-quartz stage(PyV).Gold mainly occurs in PyIII and PyIV.We find that Au,Ag,Pb,and Cu are incorporated into pyrite as micro-/nano-inclusions and that Co,Ni,As,and Se enter the pyrite lattice via isomorphous replacement.The Co/Ni values and Se concentrations indicate that PyI formed from metamorphic hydrothermal fluids and that pyrites(PyII,PyIII,and PyIV)from the ore-forming stages typically reflect a hydrothermal genesis involving magmatic fluid.Theδ^34S values of PyI(1.45‰-2.09‰)are similar to that of plagioclase amphibole schist,indicating that S was primarily derived from wall rock,while those of PyII,PyIII,and PyIV(3.10‰-5.55‰)suggest that S was derived from the Guishanyan Formation and the Laowan granite.The four mineralization stages show a systematic decrease inδD(from−77.1‰to−82.8‰,−84.7‰,and−102.7‰),while theδ^18OH2O values showed a gradual decrease from 5.7 to 2.7‰,1.0‰,and−1.3‰.These data show that the ore-forming fluid was similar to a mixture of magmatic and meteoric waters.Thus,we conclude that the Laowan gold deposit is related to magmatic-hydrothermal fluid.展开更多
Recently, iteratively reweighted methods have attracted much interest in compressed sensing, outperforming their unweighted counterparts in most cases. In these methods, decision variables and weights are optimized al...Recently, iteratively reweighted methods have attracted much interest in compressed sensing, outperforming their unweighted counterparts in most cases. In these methods, decision variables and weights are optimized alternatingly, or decision variables are optimized under heuristically chosen weights. In this paper,we present a novel weighted l1-norm minimization problem for the sparsest solution of underdetermined linear equations. We propose an iteratively weighted thresholding method for this problem, wherein decision variables and weights are optimized simultaneously. Furthermore, we prove that the iteration process will converge eventually. Using the homotopy technique, we enhance the performance of the iteratively weighted thresholding method. Finally, extensive computational experiments show that our method performs better in terms of both running time and recovery accuracy compared with some state-of-the-art methods.展开更多
Detailed routing has become much challenging in modern circuit designs due to the extreme scaling of chip size and the complicated design rules.In this paper,we give an effective algorithm for detailed routing conside...Detailed routing has become much challenging in modern circuit designs due to the extreme scaling of chip size and the complicated design rules.In this paper,we give an effective algorithm for detailed routing considering advanced technology nodes.First,we present a valid pin-access candidates generation technology for handling complex pin shapes.Then,we propose a tree-based nets components selection algorithm to decide connecting order for multiple nets components.Finally,combined with global routing results and advanced technology nodes,an initial routing results optimization algorithm is presented to achieve the final detailed routing results.Experimental results on industry benchmarks show that,our proposed algorithm not only achieves 100%routability on real industrial cases in a reasonable runtime,but also optimizes total wirelength,total vias and other advanced technology nodes simultaneously.展开更多
基金supported by the NASA GRACE and GRACE Follow-On Projects (under contract # NNL14AAOOC and JPL subcontract # 1478584)NASA ESI Program (NNX12AM86G and NNX17AG96G)NASA GRACE Science Team Program(NNX12AJ97G)
文摘Since launched in March 2002,the Gravity Recovery and Climate Experiment(GRACE)satellite gravity mission has brought a new era to the studies of large-scale mass transport and redistribution within different components of the Earth system,including the atmosphere,hydrosphere,ocean,cryosphere,and solid Earth,and greatly improved our understanding of the Earth climate system and solid Earth geophysics.This paper provides a comprehensive review of GRACE satellite gravimetry and its geophysical applications in monitoring and quantifying water mass changes in various components of the global water cycle,ice mass balance of polar ice sheets and mountain glaciers,global sea level change,and mass redistribution in solid Earth.We also discuss in detail different GRACE data products(e.g.,standard spherical harmonic and mascon solutions),commonly used GRACE data post-processing methods,major challenges in using different GRACE data and how to correctly address those challenges.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41204017,41228004,and 41274025)the Shanghai Postdoctoral Sustentation Fund (No. 13R21417900)
文摘The Gravity Recovery and Climate Experiment(GRACE) has been measuring temporal and spatial variations of mass redistribution within the Earth system since2002. As large earthquakes cause significant mass changes on and under the Earth's surface,GRACE provides a new means from space to observe mass redistribution due to earthquake deformations. GRACE serves as a good complement to other earthquake measurements because of its extensive spatial coverage and being free from terrestrial restriction. During its over 10 years mission,GRACE has successfully detected seismic gravitational changes of several giant earthquakes,which include the 2004 Sumatra–Andaman earthquake,2010 Maule(Chile) earthquake,and 2011 Tohoku-Oki(Japan) earthquake. In this review,we describe by examples how to process GRACE timevariable gravity data to retrieve seismic signals,and summarize the results of recent studies that apply GRACE observations to detect co- and post-seismic signals and constrain fault slip models and viscous lithospheric structures. We also discuss major problems and give an outlook in this field of GRACE application.
基金supported by the Natural Science Foundation of Shanghai (17ZR1435600)the Open Fund of Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, Wuhan University (16-01-05)the National Key Research and Development Program of China (2016YFB0501405)
文摘Using more than 14 years of GRACE(Gravity Recovery and Climate Experiment) satellite gravimetry observations, we estimate the ice loss rate for the Patagonia Ice Field(PIF) of South America. After correcting the effects of glacier isostatic adjustment(GIA) and hydrological variations, the ice loss rate is -23.5 ± 8.1 Giga ton per year(Gt/yr) during the period April 2002 through December 2016, equivalent to an average ice thickness change of-1.3 m/yr if evenly distributed over PIF. The PIF ice mass change series also show obvious inter-annual variations during the entire period. For the time spans April 2002 to December 2007, January 2008 to December 2012 and January 2013 to December 2016, the ice loss rates are -26.4,-9.0 and -25.0 Gt/yr, respectively, indicating that the ice melting experienced significant slowing down and accelerating again in the past decade. Comparison with time series from temperature and precipitation data over PIF suggests that the inter-annual ice losses might not be directly correlated with the temperature changes and precipitation anomalies, and thus their interrelation is intricate. However, the dramatic ice loss acceleration in 2016(with more than 100 Gt within the first half of the year) appears closely related with the evident temperature increase and severe precipitation shortage over 2016, which are likely correlated with the strong E1 Nino event around 2016. Moreover, we compare the GRACE spherical harmonic(SH) and mass concentration(Mascon) solutions in estimating the PIF ice loss rate, and find that the Mascon result has larger uncertainty in leakage error correction,while the SH solutions can better correct leakage errors based on a constrained forward modeling iterative method. Thus the GRACE SH solutions with constrained forward modeling recovery are recommended to evaluating the ice mass change of PIF or other glacier regions with relatively smaller spatial scales.
基金supported by NASA Earth Surface and Interior (ESI) Program (W.K.and J.C.)NASA Geomagnetic Infrastructure Fund+4 种基金NASA GSFC SEEC Fund (W.K.)NASA GRACE Project (J.C.)Taiwan Ministry of Science and Technology via grant 106-2116-M-001-013(B. F. Chao)NASA GSFC fellowship programIES of Academia Sinica for support of visiting tenure
文摘The observed Earth’s polar motion on decadal time scales has long been conjectured to be excited by the exchange of equatorial angular momentum between the solid mantle and the fluid outer core,via the mechanism of electromagnetic(EM)core-mantle coupling.However,past estimations of the EM coupling torque from surface geomagnetic observations is too weak to account for the observed decadal polar motion.Our recent estimations from numerical geodynamo simulations have shown the opposite.In this paper,we re-examine in detail the EM coupling mechanism and the properties of the magnetic field in the electrically conducting lower mantle(characterized by a thin D '-layer at the base of the mantle).Our simulations find that the toroidal field in the D'-layer from the induction and convection of the toroidal field in the outer core could be potentially much stronger than that from the advection of the poloidal field in the outer core.The former,however,cannot be inferred from geomagnetic observations at the Earth’s surface,and is missing in previous EM torque estimated from geomagnetic observations.Our deduction suggests further that this field could make the actual EM coupling torque sufficiently strong,at approximately 5×1019 Nm,to excite,and hence explain,the decadal polar motion to magnitude of approximately 10 mas.
基金This research was funded by the US National Science Foundation(NSF)(Grant Nos.1952140,2038967,and 2026719).
文摘Indoor environment has significant impacts on human health as people spend 90%of their time indoors.The COVID-19 pandemic and the increased public health awareness have further elevated the urgency for cultivating and maintaining a healthy indoor environment.The advancement in emerging digital twin technologies including building information modeling(BIM),Internet of Things(IoT),data analytics,and smart control have led to new opportunities for building design and operation.Despite the numerous studies on developing methods for creating digital twins and enabling new functionalities and services in smart building management,very few have focused on the health of indoor environment.There is a critical need for understanding and envisaging how digital twin paradigms can be geared towards healthy indoor environment.Therefore,this study reviews the techniques for developing digital twins and discusses how the techniques can be customized to contribute to public health.Specifically,the current applications of BIM,IoT sensing,data analytics,and smart building control technologies for building digital twins are reviewed,and the knowledge gaps and limitations are discussed to guide future research for improving environmental and occupant health.Moreover,this paper elaborates a vision for future research on integrated digital twins for a healthy indoor environment with special considerations of the above four emerging techniques and issues.This review contributes to the body of knowledge by advocating for the consideration of health in digital twin modeling and smart building services and presenting the research roadmap for digital twin-enabled healthy indoor environment.
基金Project supported by the Natural Science Foundation of Tianjin,China(No.15JCQNJC03700)the National Natural Science Foundation of China(Nos.51702297)
文摘A series of AIN nanostructures were synthesized by an ultrahigh-temperature, catalyst-free, physical vapor transport(PVT) process. Energy dispersive X-ray spectroscopy(EDX), X-ray diffraction(XRD), X-Ray photoelectron spectroscopy(XPS),high resolution transmission electron microscopy(HRTEM) detection show that high quality AIN nanowires were prepared. Nanostructures including nanorings, nanosprings, nanohelices, chainlike nanowires, six-fold symmetric nanostructure and rod-like structure were successfully obtained by controlling the growth duration and temperature. The morphology evolution was attributed to electrostatic polar charge model and the crystalline lattice structure of AIN.
基金This research was supported by the Project of the Nanyang Basin and Orogenic Belt Metallogenic Diversity Research(No.2014-49)supported by No.1 Geological Exploration Institute,Henan Bureau of Geo-exploration and Mineral Development.
文摘The Laowan deposit is a large gold deposit in the Qinling-Dabie orogenic belt where pyrite is the main Au-bearing mineral phase.We present results from the occurrences of gold,trace elements and sulfur isotopes of pyrite,and hydrogen and oxygen isotopes of quartz and calcite to elucidate the sources of ore-forming fluid;the genesis of pyrite and the ore-forming process.From field observations,five generations of pyrite are identified;one formed in a metamorphic-diagenetic epoch(PyI),and the others during four mineralization stages:1)the coarse-grained pyrite-quartz stage(PyII),2)the quartz and medium-to fine-grained pyrite stage(PyIII),3)the polymetallic sulfide stage(PyIV),and 4)the carbonate-quartz stage(PyV).Gold mainly occurs in PyIII and PyIV.We find that Au,Ag,Pb,and Cu are incorporated into pyrite as micro-/nano-inclusions and that Co,Ni,As,and Se enter the pyrite lattice via isomorphous replacement.The Co/Ni values and Se concentrations indicate that PyI formed from metamorphic hydrothermal fluids and that pyrites(PyII,PyIII,and PyIV)from the ore-forming stages typically reflect a hydrothermal genesis involving magmatic fluid.Theδ^34S values of PyI(1.45‰-2.09‰)are similar to that of plagioclase amphibole schist,indicating that S was primarily derived from wall rock,while those of PyII,PyIII,and PyIV(3.10‰-5.55‰)suggest that S was derived from the Guishanyan Formation and the Laowan granite.The four mineralization stages show a systematic decrease inδD(from−77.1‰to−82.8‰,−84.7‰,and−102.7‰),while theδ^18OH2O values showed a gradual decrease from 5.7 to 2.7‰,1.0‰,and−1.3‰.These data show that the ore-forming fluid was similar to a mixture of magmatic and meteoric waters.Thus,we conclude that the Laowan gold deposit is related to magmatic-hydrothermal fluid.
基金supported by National Natural Science Foundation of China(Grant Nos.61672005 and 11571074)。
文摘Recently, iteratively reweighted methods have attracted much interest in compressed sensing, outperforming their unweighted counterparts in most cases. In these methods, decision variables and weights are optimized alternatingly, or decision variables are optimized under heuristically chosen weights. In this paper,we present a novel weighted l1-norm minimization problem for the sparsest solution of underdetermined linear equations. We propose an iteratively weighted thresholding method for this problem, wherein decision variables and weights are optimized simultaneously. Furthermore, we prove that the iteration process will converge eventually. Using the homotopy technique, we enhance the performance of the iteratively weighted thresholding method. Finally, extensive computational experiments show that our method performs better in terms of both running time and recovery accuracy compared with some state-of-the-art methods.
文摘Detailed routing has become much challenging in modern circuit designs due to the extreme scaling of chip size and the complicated design rules.In this paper,we give an effective algorithm for detailed routing considering advanced technology nodes.First,we present a valid pin-access candidates generation technology for handling complex pin shapes.Then,we propose a tree-based nets components selection algorithm to decide connecting order for multiple nets components.Finally,combined with global routing results and advanced technology nodes,an initial routing results optimization algorithm is presented to achieve the final detailed routing results.Experimental results on industry benchmarks show that,our proposed algorithm not only achieves 100%routability on real industrial cases in a reasonable runtime,but also optimizes total wirelength,total vias and other advanced technology nodes simultaneously.