Existing empirical methods for interpreting the consolidation yield stress and the overconsolidation ratio （OCR） in clays from piezocone tests are briefly reviewed. It can be seen that no universal correlation exist...Existing empirical methods for interpreting the consolidation yield stress and the overconsolidation ratio （OCR） in clays from piezocone tests are briefly reviewed. It can be seen that no universal correlation exists for all worldwide sites. However, for a given clay deposit, there does exist a most appropriate method to reflect the consolidation yield stress and the OCR based on piezocone test data. Three empirical methods are compared based on the piezocone test data collected on Lixia River lagoonal deposit soil sites in the north of Jiangsu province. The objective of this study is to evaluate the validity of the existing relationships linking the consolidation yield stress to piezocone test data and identify the appropriate method for Lixia River lagoonal deposit soil. It is shown that the correlation based on the net tip resistance has much higher accuracy for estimating the consolidation yield stress of lagoonal deposit soil than other methods.展开更多
The study area is located in the south of Huanxian county,in Yan'an and Puxian counties and to the north of Xi'an.The Shanxi and lower Shihezi formations are important gas-bearing formations.Given our analysis...The study area is located in the south of Huanxian county,in Yan'an and Puxian counties and to the north of Xi'an.The Shanxi and lower Shihezi formations are important gas-bearing formations.Given our analysis of the direction of rivers,the contents of stable heavy minerals and of feldspar of palaeo river systems,the study area is divided into six palaeodrainage patterns corresponding to six feldspar regions and six sedimentary facies regions.On this basis,the distribution of sedimentary facies was also analyzed.During the Shanxi stage,a delta front was deposited in the Huanxian region and delta plains and fronts were deposited in the Pingliang,Chunhua-Yaoxian and Hancheng-Chengcheng regions.In the Yan'an-Daning region,only a delta front was developed.The distribution of sedimentary facies in the earlier Shihezi stage originated from the Shanxi stage.A delta front was developed in the Huanxian region while a delta plain and front developed in the Pingliang-Zhenyuan region during the same time.Lakes originated only in the Zhenyuan-Huanxian-Huachi-Zhengning and Daning-Jixian zones.This analytical method shows that different palaeodrainage patterns can be effectively distinguished in order to forecast sedimentary facies.展开更多
Given sustaining exploration, the eastern zone of the Sulige gas field may soon become a key area of exploitation. In order to explore its genesis, types and distribution of the reservoir sandstones in the eastern zon...Given sustaining exploration, the eastern zone of the Sulige gas field may soon become a key area of exploitation. In order to explore its genesis, types and distribution of the reservoir sandstones in the eastern zone of this gas field, we focused in our study on the provenance and detailed sedimentary facies of sandstone of the He8 （the eighth part of the Shihezi formation, Permian system） and Shanxil （the first part of the Shanxi formation, Permian system） members, based on core observations, analyses in petrography, granularity and logging. The results show that： 1） the sandstone provenance of Shanxil and He8 in the eastern zone of the Sulige gas field is from the north of the Ordos Basin, characterized by dual directions from the north and northeast. 2） The He8 and Shanxil members were deposited in a fluvial-delta sedimentary system. The He8 was mainly deposited in braided rivers, in- cluding braided channels, channel bars, levee and floodplain sub-environments, whereas the Shanxil Member was deposited in braided rivers and deltas, including braided channels, channel bars, floodplains, tributaries and inter-tributary sub-environments. 3） Sedimentary facies bands migrated in drastic fashion towards the basin from the Shanxil to the He8 Member. Base levels of sedi- mentation generally present a trend of small increases in-amplitude, large decreasing amplitudes and slow and gradual Increases. 4） The continuity of the reservoir sandbodies along the source direction is better than that perpendicular to the direction. Compared with Shanxil, both dimensions and continuity of the sandbodies in He8 are better from which we conclude that it is the most fa- vorable part of the reservoir.展开更多
Based on field observation,core description and well logging analysis,the tectonic-sedimentary framework of the Liangshan and Qixia Formations in the northwestern Sichuan Basin,China is deeply discussed.Two long-term ...Based on field observation,core description and well logging analysis,the tectonic-sedimentary framework of the Liangshan and Qixia Formations in the northwestern Sichuan Basin,China is deeply discussed.Two long-term sequence cycles were identified,denoted as LSC1 and LSC2,respectively.The sequence stratigraphic framework was established,suggesting the Liangshan Formation to be not isochronously deposited.Paleogeomorphy before deposition of LSC1 was reconstructed by the impression method.LSC1 was featured by thin,low-energy shoal deposits in the high topography,and thick inter-shoal sea and open sea deposits in the low topography.Meanwhile,paleogeomorphy before deposition of LSC2 was reconstructed using the residual thickness method,which was demonstrated to have primary high-energy,thick shoal deposits in the high topography,and thin inter-shoal and open sea deposits in the low topography.The results show that differential tectonic subsidence has already taken place during the Qixia Period,and thus the Dongwu Movement should occur earlier than previously expected.Meanwhile,pre-depositional paleogeomorphy has obvious controlling effects on the sequence stratigraphic filling and sedimentary facies distribution.Results of this study were expected to provide practical guidance to fine characterization of the sedimentary evolution process and prediction of high-quality reservoir distribution.展开更多
Ecosystem response to climate change in high-altitude regions is a focus on global change research. Picea/Abies forests are widely distributed at high altitudes of East and Central Asia, and their distribution changes...Ecosystem response to climate change in high-altitude regions is a focus on global change research. Picea/Abies forests are widely distributed at high altitudes of East and Central Asia, and their distribution changes are sensitive to climate change. Humidity is an important climatic factor that affects high-altitude ecosystems; however, the relationship between distribution changes of Picea/Abies forests and millennial-scale variability of humidity is still not dear. Palynological records can provide insights into millennial-scale paleovegetation changes, which have been successfully used to reconstruct past climate change in East and Central Asia. In this study, we synthesized 24 Picea/Abies pollen and humidity/moisture changes based upon Holocene lake records in East and Central Asia in order to explore the response of high-latitude ecosystem to millennial-scale climate change. The changing pattern of Holocene lacustrine Picea/Abies pollen in arid Central Asia differs from that of monsoonal East Asia, which can be due to different millennial-scale climate change patterns between monsoonal and arid Central Asia. Then, the relationship between changes in Picea/Abies pollen and humidity/moisture conditions was examined based on a comparison of pollen and humidity/moisture records. The results indicate that millennial-scale Picea/Abies distribution changes aremainly controlled by moisture variability at high altitudes, while the temperature effect plays a minor role in Picea/Abies distribution changes. Moreover, this research proves that lacustrine Picea/Abies pollen can be used as an indicator of millennial-scale humidity/moisture evolution at high altitudes in East and Central Asia.展开更多
The paper describes the sedimentary features and biostratigraphy of the transitional Jurassic to Cretaceous deposits in the continental basins of Priamurie formed after the collision between the Siberian and North Chi...The paper describes the sedimentary features and biostratigraphy of the transitional Jurassic to Cretaceous deposits in the continental basins of Priamurie formed after the collision between the Siberian and North China blocks. In Upper Priamurie, the collision occurred in the late Early Jurassic as dated by the emplacement of the post-collisional granites （ 191 Ma）. While in Lower Priamurie and West Priokhotie it could take place in the late Middle Jurassic on the basis of fossil evidence from an aceretionary turbidite complex. This event reflected the environmental change from coastal-marine to alluvial plains, often boggy, where coals aecmnulated. The environinental change is in harmony with that of biota. Systematic study of floral and spores/pollen assemblages, particularly in the sections of interbedded marine and non-marine deposits, makes clear the chronostrati-graphic succession of floral associations and shows the possibility of their application for subdivision and correlation of the continental deposits of Priamurie. Tire coastal-marine environment of the residual post-collisional sublatitudinal basins in the uestern part of Priamurie （Upper Amur and Dep basins） was replaced by the continental in the late Middle Jurassic and in the eastern part in the Berriasian-Valanginian （Torom Basin）. Similar environmental change commenced in the submeridional rift basins： the Bureya Basin in the Callovian and the Partizansk Basin in the Hauterivian. Changes in ecosystems ocemTed frequently during the Middle Jurassic-Ne- ocomian, but the most substantial changes took place in the late Middle Jurassic and in the end of Late Jurassie.展开更多
Realizing low contact resistance between graphene and metal electrodes remains a well-known challenge for building high-performance graphene devices. In this work, we attempt to reduce the contact resistance in graphe...Realizing low contact resistance between graphene and metal electrodes remains a well-known challenge for building high-performance graphene devices. In this work, we attempt to reduce the contact resistance in graphene transistors and further explore the resistance limit between graphene and metal contacts. The Pd/graphene contact resistance at room temperature is reduced below the 100 Ω·μm level both on mechanically exfoliated and chemical-vapor-deposition graphene by adopting high-purity palladium and high-quality graphene and controlling the fabrication process to not contaminate the interface. After excluding the parasitic series resistances from the measurement system and electrodes, the retrieved contact resistance is shown to be systematically and statistically less than 100 Ω·μm, with a minimum value of 69 Ω·μm, which is very close to the theoretical limit. Furthermore, the contact resistance shows no clear dependence on temperature in the range of 77-300 K; this is attributed to the saturation of carrier injection efficiency between graphene and Pd owing to the high quality of the graphene samples used, which have a sufficiently long carrier mean-free-path.展开更多
We integrate the lattice Boltzmann method(LBM) and immersed boundary method(IBM) to capture the coupling between a rigid boundary surface and the hydrodynamic response of an enclosed particle laden fluid. We focus on ...We integrate the lattice Boltzmann method(LBM) and immersed boundary method(IBM) to capture the coupling between a rigid boundary surface and the hydrodynamic response of an enclosed particle laden fluid. We focus on a rigid box filled with a Newtonian fluid where the drag force based on the slip velocity at the wall and settling particles induces the interaction. We impose an external harmonic oscillation on the system boundary and found interesting results in the sedimentation behavior. Our results reveal that the sedimentation and particle locations are sensitive to the boundary walls oscillation amplitude and the subsequent changes on the enclosed flow field. Two different particle distribution analyses were performed and showed the presence of an agglomerate structure of particles. Despite the increase in the amplitude of wall motion, the turbulence level of the flow field and distribution of particles are found to be less in quantity compared to the stationary walls. The integrated LBM-IBM methodology promised the prospect of an efficient and accurate dynamic coupling between a non-compliant bounding surface and flow field in a wide-range of systems. Understanding the dynamics of the fluid-filled box can be particularly important in a simulation of particle deposition within biological systems and other engineering applications.展开更多
基金Jiangsu Transportation Research Program Fund (No03Y007)
文摘Existing empirical methods for interpreting the consolidation yield stress and the overconsolidation ratio （OCR） in clays from piezocone tests are briefly reviewed. It can be seen that no universal correlation exists for all worldwide sites. However, for a given clay deposit, there does exist a most appropriate method to reflect the consolidation yield stress and the OCR based on piezocone test data. Three empirical methods are compared based on the piezocone test data collected on Lixia River lagoonal deposit soil sites in the north of Jiangsu province. The objective of this study is to evaluate the validity of the existing relationships linking the consolidation yield stress to piezocone test data and identify the appropriate method for Lixia River lagoonal deposit soil. It is shown that the correlation based on the net tip resistance has much higher accuracy for estimating the consolidation yield stress of lagoonal deposit soil than other methods.
基金Projects OF06142 supported by the National Basic Research Program of China2001CB209100 by the Science Foundation of China University of Mining and Technology
文摘The study area is located in the south of Huanxian county,in Yan'an and Puxian counties and to the north of Xi'an.The Shanxi and lower Shihezi formations are important gas-bearing formations.Given our analysis of the direction of rivers,the contents of stable heavy minerals and of feldspar of palaeo river systems,the study area is divided into six palaeodrainage patterns corresponding to six feldspar regions and six sedimentary facies regions.On this basis,the distribution of sedimentary facies was also analyzed.During the Shanxi stage,a delta front was deposited in the Huanxian region and delta plains and fronts were deposited in the Pingliang,Chunhua-Yaoxian and Hancheng-Chengcheng regions.In the Yan'an-Daning region,only a delta front was developed.The distribution of sedimentary facies in the earlier Shihezi stage originated from the Shanxi stage.A delta front was developed in the Huanxian region while a delta plain and front developed in the Pingliang-Zhenyuan region during the same time.Lakes originated only in the Zhenyuan-Huanxian-Huachi-Zhengning and Daning-Jixian zones.This analytical method shows that different palaeodrainage patterns can be effectively distinguished in order to forecast sedimentary facies.
基金supported by the National Basic Re-search Program of China (No2003CB214603)
文摘Given sustaining exploration, the eastern zone of the Sulige gas field may soon become a key area of exploitation. In order to explore its genesis, types and distribution of the reservoir sandstones in the eastern zone of this gas field, we focused in our study on the provenance and detailed sedimentary facies of sandstone of the He8 （the eighth part of the Shihezi formation, Permian system） and Shanxil （the first part of the Shanxi formation, Permian system） members, based on core observations, analyses in petrography, granularity and logging. The results show that： 1） the sandstone provenance of Shanxil and He8 in the eastern zone of the Sulige gas field is from the north of the Ordos Basin, characterized by dual directions from the north and northeast. 2） The He8 and Shanxil members were deposited in a fluvial-delta sedimentary system. The He8 was mainly deposited in braided rivers, in- cluding braided channels, channel bars, levee and floodplain sub-environments, whereas the Shanxil Member was deposited in braided rivers and deltas, including braided channels, channel bars, floodplains, tributaries and inter-tributary sub-environments. 3） Sedimentary facies bands migrated in drastic fashion towards the basin from the Shanxil to the He8 Member. Base levels of sedi- mentation generally present a trend of small increases in-amplitude, large decreasing amplitudes and slow and gradual Increases. 4） The continuity of the reservoir sandbodies along the source direction is better than that perpendicular to the direction. Compared with Shanxil, both dimensions and continuity of the sandbodies in He8 are better from which we conclude that it is the most fa- vorable part of the reservoir.
基金Project(41802147)supported by the National Natural Science Foundation of ChinaProject(2016ZX05007-004)supported by the National Major Science and Technology Projects of China。
文摘Based on field observation,core description and well logging analysis,the tectonic-sedimentary framework of the Liangshan and Qixia Formations in the northwestern Sichuan Basin,China is deeply discussed.Two long-term sequence cycles were identified,denoted as LSC1 and LSC2,respectively.The sequence stratigraphic framework was established,suggesting the Liangshan Formation to be not isochronously deposited.Paleogeomorphy before deposition of LSC1 was reconstructed by the impression method.LSC1 was featured by thin,low-energy shoal deposits in the high topography,and thick inter-shoal sea and open sea deposits in the low topography.Meanwhile,paleogeomorphy before deposition of LSC2 was reconstructed using the residual thickness method,which was demonstrated to have primary high-energy,thick shoal deposits in the high topography,and thin inter-shoal and open sea deposits in the low topography.The results show that differential tectonic subsidence has already taken place during the Qixia Period,and thus the Dongwu Movement should occur earlier than previously expected.Meanwhile,pre-depositional paleogeomorphy has obvious controlling effects on the sequence stratigraphic filling and sedimentary facies distribution.Results of this study were expected to provide practical guidance to fine characterization of the sedimentary evolution process and prediction of high-quality reservoir distribution.
基金supported by the National Natural Science Foundation of China (Grant No. 41371009)the Fundamental Research Fund for the Central Universities of China (Grant No. lzujbky2013-127)
文摘Ecosystem response to climate change in high-altitude regions is a focus on global change research. Picea/Abies forests are widely distributed at high altitudes of East and Central Asia, and their distribution changes are sensitive to climate change. Humidity is an important climatic factor that affects high-altitude ecosystems; however, the relationship between distribution changes of Picea/Abies forests and millennial-scale variability of humidity is still not dear. Palynological records can provide insights into millennial-scale paleovegetation changes, which have been successfully used to reconstruct past climate change in East and Central Asia. In this study, we synthesized 24 Picea/Abies pollen and humidity/moisture changes based upon Holocene lake records in East and Central Asia in order to explore the response of high-latitude ecosystem to millennial-scale climate change. The changing pattern of Holocene lacustrine Picea/Abies pollen in arid Central Asia differs from that of monsoonal East Asia, which can be due to different millennial-scale climate change patterns between monsoonal and arid Central Asia. Then, the relationship between changes in Picea/Abies pollen and humidity/moisture conditions was examined based on a comparison of pollen and humidity/moisture records. The results indicate that millennial-scale Picea/Abies distribution changes aremainly controlled by moisture variability at high altitudes, while the temperature effect plays a minor role in Picea/Abies distribution changes. Moreover, this research proves that lacustrine Picea/Abies pollen can be used as an indicator of millennial-scale humidity/moisture evolution at high altitudes in East and Central Asia.
文摘The paper describes the sedimentary features and biostratigraphy of the transitional Jurassic to Cretaceous deposits in the continental basins of Priamurie formed after the collision between the Siberian and North China blocks. In Upper Priamurie, the collision occurred in the late Early Jurassic as dated by the emplacement of the post-collisional granites （ 191 Ma）. While in Lower Priamurie and West Priokhotie it could take place in the late Middle Jurassic on the basis of fossil evidence from an aceretionary turbidite complex. This event reflected the environmental change from coastal-marine to alluvial plains, often boggy, where coals aecmnulated. The environinental change is in harmony with that of biota. Systematic study of floral and spores/pollen assemblages, particularly in the sections of interbedded marine and non-marine deposits, makes clear the chronostrati-graphic succession of floral associations and shows the possibility of their application for subdivision and correlation of the continental deposits of Priamurie. Tire coastal-marine environment of the residual post-collisional sublatitudinal basins in the uestern part of Priamurie （Upper Amur and Dep basins） was replaced by the continental in the late Middle Jurassic and in the eastern part in the Berriasian-Valanginian （Torom Basin）. Similar environmental change commenced in the submeridional rift basins： the Bureya Basin in the Callovian and the Partizansk Basin in the Hauterivian. Changes in ecosystems ocemTed frequently during the Middle Jurassic-Ne- ocomian, but the most substantial changes took place in the late Middle Jurassic and in the end of Late Jurassie.
基金This work was supported by the Ministry of Sdence and Technology of China （Grant Nos. 2011CB933001 and 2011CB933002）, National Natural Science Foundation of China （Grant Nos. 61322105, 61271051, 61321001, and 61390504）, and Beijing Municipal Science and Technology Commission （Grant Nos. Z131100003213021 and D141100000614001）.
文摘Realizing low contact resistance between graphene and metal electrodes remains a well-known challenge for building high-performance graphene devices. In this work, we attempt to reduce the contact resistance in graphene transistors and further explore the resistance limit between graphene and metal contacts. The Pd/graphene contact resistance at room temperature is reduced below the 100 Ω·μm level both on mechanically exfoliated and chemical-vapor-deposition graphene by adopting high-purity palladium and high-quality graphene and controlling the fabrication process to not contaminate the interface. After excluding the parasitic series resistances from the measurement system and electrodes, the retrieved contact resistance is shown to be systematically and statistically less than 100 Ω·μm, with a minimum value of 69 Ω·μm, which is very close to the theoretical limit. Furthermore, the contact resistance shows no clear dependence on temperature in the range of 77-300 K; this is attributed to the saturation of carrier injection efficiency between graphene and Pd owing to the high quality of the graphene samples used, which have a sufficiently long carrier mean-free-path.
基金supported by the National Natural Science Foundation of China(Grant No.11372068)the National Key Basic Research and Development Program of China(Grant No.2014CB744104)
文摘We integrate the lattice Boltzmann method(LBM) and immersed boundary method(IBM) to capture the coupling between a rigid boundary surface and the hydrodynamic response of an enclosed particle laden fluid. We focus on a rigid box filled with a Newtonian fluid where the drag force based on the slip velocity at the wall and settling particles induces the interaction. We impose an external harmonic oscillation on the system boundary and found interesting results in the sedimentation behavior. Our results reveal that the sedimentation and particle locations are sensitive to the boundary walls oscillation amplitude and the subsequent changes on the enclosed flow field. Two different particle distribution analyses were performed and showed the presence of an agglomerate structure of particles. Despite the increase in the amplitude of wall motion, the turbulence level of the flow field and distribution of particles are found to be less in quantity compared to the stationary walls. The integrated LBM-IBM methodology promised the prospect of an efficient and accurate dynamic coupling between a non-compliant bounding surface and flow field in a wide-range of systems. Understanding the dynamics of the fluid-filled box can be particularly important in a simulation of particle deposition within biological systems and other engineering applications.
