The development of pores in a clastic reservoir is one of the most important research subjects in oil-gas exploration and development, whereas the many reasons for the formation of secondary porosity have increased th...The development of pores in a clastic reservoir is one of the most important research subjects in oil-gas exploration and development, whereas the many reasons for the formation of secondary porosity have increased the degree of difficulty in such research. Thus the research aims are to discover the controlling factors of solutional voids in feldspars and to predict favorable regions for these voids. Macroscopic and systematic researches into the relationship between the kaolinite content in the feldspar solutional void developed area of the Chang 2 reservoir group of the Triassic Yanchang Formation in the Midwest Ordos Basin and the solutional void in feldspar have been made, and from this it can be determined that the kaolinite content has an indicative function to the distribution of the solutional void in feldspar. Solutional void in feldspar is relatively well developed at the area where kaolinite content is high. Although the factors affecting kaolinite content are complicated, yet that of the research area is mainly affected by the impact of the leaching atmospheric water acting on the palaeogeomorphology. Three favorable zone belts for the development of solutional voids in feldspars are forecasted on the basis of restoration of palaeogeomorphology.展开更多
1 Introduction Yanchang Formation in Upper Triassic,Ordos basin contains the most abundant hydrocarbon resources in North China(Wang et al.,2014).The sandstones are the most important oil-bearing reservoirs in Yanchang
Characteristics of Chang 21 low permeability sandstone reservoir of Shunning oil field are analyzed and evaluated based on the data of well logging and experiment. The result shows that 1) the Chang 21 low permeabilit...Characteristics of Chang 21 low permeability sandstone reservoir of Shunning oil field are analyzed and evaluated based on the data of well logging and experiment. The result shows that 1) the Chang 21 low permeability reservoir belongs to the classification of middle-to-fine sized feldspar sandstone, with its components being low in ma- turity, deposited in distributary rivers in the front of the delta; 2) the reservoir is obviously dominated by a low or a very low permeability with a linear variation tendency different from that of the ultra-low permeability reservoir; 3) the spa- tial variation in lithology and physical properties of the reservoir are controlled by the sedimentary facies zones, and 4) the physical property of the reservoir is significantly influenced by clastic constituents and their structure, and the con- stituent of cement materials and their content. The result also shows that the diagenesis action of the reservoir is quite strong in which dissolution greatly modified the reservoir In addition, the inter-granular dissolved pores are the mainly developed ones and the micro-structure is dominated by the combination of middle-to-large sized pores with fine-to-coarse throats. Finally, the radius of the throats is in good exponential correlation with permeability and the seepage capacity comes from those large sized throats.展开更多
Chang＇e-2, Chinese second lunar probe, was inserted into a 100 km altitude low lunar orbit on October 9th, 2010, its purpose is to continuously photograph the lunar surface and possibly chosen landing sites for futur...Chang＇e-2, Chinese second lunar probe, was inserted into a 100 km altitude low lunar orbit on October 9th, 2010, its purpose is to continuously photograph the lunar surface and possibly chosen landing sites for future lunar missions. The probe will still carry considerable amount of propellant after completing all prescribed tasks in about six months. After the successful launch of Chang＇e-2, we began designing the probe＇s subsequent flight scenario, considering a total impulse of 1 100 m/s for takeoff from low lunar orbit and a maximum 3× 10^6 km distance for Earth-probe telecom- munication. Our first-round effort proposed a preliminary flight scenario that involves consecutive arrivals at the halo orbits around the Earth-Moon L1/L2 and Sun-Earth L1/L2 points, near-Earth asteroid flyby, Earth return, and lunar impact. The designed solution of Chang＇e-2＇s subsequent flight scenario is a multi-segment flight trajectory that serves as a reference for making the final decision on Chang＇e-2＇s extended mission, which is a flight to the Sun-Earth L2 point, and a possible scheme of lunar impact via Earth flyby after remaining at the Sun-Earth L2 point was also presented. The proposed flight trajectory, which possesses acceptable solution accuracy for mission analysis, is a novel design that effectively exploits the invariant manifolds in the circular restricted three-body problem and the patched-manifold-conic method.展开更多
Driven by curiosity about possible flight options for the Chang＇e-2 spacecraft after it remains at the Sun-Earth L2 point, effective approaches were developed for designing preliminary fuel-optimal near-Earth asteroi...Driven by curiosity about possible flight options for the Chang＇e-2 spacecraft after it remains at the Sun-Earth L2 point, effective approaches were developed for designing preliminary fuel-optimal near-Earth asteroid flyby trajectories. The approaches include the use of modified unstable manifolds, grid search of the manifolds＇ parameters, and a two-impulse maneuver for orbital phase matching and z-axis bias change, and are demonstrated to be effective in asteroid target screening and trajectory optimization. Asteroid flybys are expected to be within a distance of 2 × 10^7 km from the Earth owing to the constrained Earth-spacecraft communication range. In this case, the spacecraft＇s orbital motion is significantly affected by the gravities of both the Sun and the Earth, and therefore, the concept of the ＂he- liocentric oscillating-Kepler orbit＂ is proposed, because the classical orbital elements of the flyby trajectories referenced in the heliocentric inertial frame oscillate significantly with respect to time. The analysis and results presented in this study show that, among the asteroids whose orbits are the most accurately predicted, ＂Toutatis＂, ＂2005 NZ6＂, or ＂2010 CL19＂ might be encountered by Chang＇e-2 in late 2012 or 2013 with total impulses less than 100 rn/s.展开更多
Shape modeling is fundamental to the analysis of dynamic environment and motion around asteroid. Chang＇E- 2 successfully made a flyby of Asteroid 4179 Toutatis and obtained plenty of high-resolution images during the...Shape modeling is fundamental to the analysis of dynamic environment and motion around asteroid. Chang＇E- 2 successfully made a flyby of Asteroid 4179 Toutatis and obtained plenty of high-resolution images during the mis- sion. In this paper, the modeling method and preliminary model of Asteroid Toutatis are discussed. First, the optical images obtained by Chang＇E-2 are analyzed. Terrain and silhouette features in images are described. Then, the modeling method based on previous radar model and preliminary information from optical images is proposed. A preliminary polyhedron model of Asteroid Toutatis is established. Finally, the spherical harmonic coefficients of Asteroid Toutatis based on the polyhedron model are obtained. Some parameters of model are analyzed and compared. Although the model proposed in this paper is only a preliminary model, this work offers a valuable reference for future high-resolution models.展开更多
目的:评价基于跨理论模型的护理干预对2型糖尿病病人自我管理能力等方面的干预效果。方法:检索PubMed、Web of Science、the Cochrane Library、Embase、中国知网、维普数据库、万方数据库和中国生物医学文献数据库,检索时限为建库至202...目的:评价基于跨理论模型的护理干预对2型糖尿病病人自我管理能力等方面的干预效果。方法:检索PubMed、Web of Science、the Cochrane Library、Embase、中国知网、维普数据库、万方数据库和中国生物医学文献数据库,检索时限为建库至2023年1月11日,收集基于跨理论模型的护理干预提高2型糖尿病病人自我管理能力的随机对照试验,采用RevMan 5.2软件进行数据分析。结果:共纳入12篇文献,共计1513例病人。Meta分析结果显示,基于跨理论模型的护理干预可提高病人自我管理能力[SMD=0.69,95%CI(0.50,0.88),P<0.05]、自我效能[SMD=0.85,95%CI(0.64,1.06),P<0.05],改善生活质量[SMD=0.79,95%CI(0.18,1.40),P<0.05]。结论:现有证据表明基于跨理论模型的护理干预可以有效提高2型糖尿病病人的自我管理能力和自我效能,改善病人的生活质量,目前还需要大样本、高质量的临床研究验证结果。展开更多
We elucidate the importance of a capping layer on the structural evolution and phase change properties of carbondoped Ge2 Sb2 Te5（C-GST） films during heating in air. Both the C-GST films without and with a thin SiO2...We elucidate the importance of a capping layer on the structural evolution and phase change properties of carbondoped Ge2 Sb2 Te5（C-GST） films during heating in air. Both the C-GST films without and with a thin SiO2 capping layer（C-GST and C-GST/SiO2） are deposited for comparison. Large differences are observed between C-GST and C-GST/SiO2 films in resistance-temperature, x-ray diffraction, x-ray photoelectron spectroscopy,Raman spectra, data retention capability and optical band gap measurements. In the C-GST film, resistancetemperature measurement reveals an unusual smooth decrease in resistance above 110℃ during heating. Xray diffraction result has excluded the possibility of phase change in the C-GST film below 170℃. The x-ray photoelectron spectroscopy experimental result reveals the evolution of Te chemical valence because of the carbon oxidation during heating. Raman spectra further demonstrate that phase changes from an amorphous state to the hexagonal state occur directly during heating in the C-GST film. The quite smooth decrease in resistance is believed to be related with the formation of Te-rich GeTe4-n Gen（n = 0, 1） units above 110℃ in the C-GST film. The oxidation of carbon is harmful to the C-GST phase change properties.展开更多
This study examined the mass change of the Antarctic ice sheet(AIS) based on ICESat and CryoSat-2 observations. We estimated the AIS exhibited mass losses of-101±15 Gt·aduring the ICESat period(Sept–Nov 200...This study examined the mass change of the Antarctic ice sheet(AIS) based on ICESat and CryoSat-2 observations. We estimated the AIS exhibited mass losses of-101±15 Gt·aduring the ICESat period(Sept–Nov 2003 to Sept–Oct 2009) and-186±55 Gt·aduring the CryoSat-2 period(Jan 2011 to Dec 2015). Mass losses occurred mainly in the sectors of the Amundsen and Bellingshausen seas. Benefitting from the 30-d subcycle of CryoSat-2, we obtained monthly estimates of mass evolution. Considerable annual variations were observed in the mass evolution sequences and the climatological monthly mass evolution. Seasonal mass evolutions in the sectors of the Bellingshausen and Amundsen seas were found most representative of the annual variation. The geographical distribution characteristics of interannual AIS mass evolution were revealed by the annual average mass evolution sequences. During Jan 2011 to Dec 2015, the ice sheets in the sectors of the Bellingshausen and Amundsen seas, and the Totten Glacier, experienced increasingly rapid areal mass loss. An area of mass gain with a moderate rate of increase was found between Dronning Maud Land and Enderby Land. Rapid mass accumulation has occurred in a limited area of the Kamb Ice Stream.展开更多
文摘The development of pores in a clastic reservoir is one of the most important research subjects in oil-gas exploration and development, whereas the many reasons for the formation of secondary porosity have increased the degree of difficulty in such research. Thus the research aims are to discover the controlling factors of solutional voids in feldspars and to predict favorable regions for these voids. Macroscopic and systematic researches into the relationship between the kaolinite content in the feldspar solutional void developed area of the Chang 2 reservoir group of the Triassic Yanchang Formation in the Midwest Ordos Basin and the solutional void in feldspar have been made, and from this it can be determined that the kaolinite content has an indicative function to the distribution of the solutional void in feldspar. Solutional void in feldspar is relatively well developed at the area where kaolinite content is high. Although the factors affecting kaolinite content are complicated, yet that of the research area is mainly affected by the impact of the leaching atmospheric water acting on the palaeogeomorphology. Three favorable zone belts for the development of solutional voids in feldspars are forecasted on the basis of restoration of palaeogeomorphology.
基金financially supported by the National Natural Science Foundation of China (grant No. 41272115)
文摘1 Introduction Yanchang Formation in Upper Triassic,Ordos basin contains the most abundant hydrocarbon resources in North China(Wang et al.,2014).The sandstones are the most important oil-bearing reservoirs in Yanchang
文摘Characteristics of Chang 21 low permeability sandstone reservoir of Shunning oil field are analyzed and evaluated based on the data of well logging and experiment. The result shows that 1) the Chang 21 low permeability reservoir belongs to the classification of middle-to-fine sized feldspar sandstone, with its components being low in ma- turity, deposited in distributary rivers in the front of the delta; 2) the reservoir is obviously dominated by a low or a very low permeability with a linear variation tendency different from that of the ultra-low permeability reservoir; 3) the spa- tial variation in lithology and physical properties of the reservoir are controlled by the sedimentary facies zones, and 4) the physical property of the reservoir is significantly influenced by clastic constituents and their structure, and the con- stituent of cement materials and their content. The result also shows that the diagenesis action of the reservoir is quite strong in which dissolution greatly modified the reservoir In addition, the inter-granular dissolved pores are the mainly developed ones and the micro-structure is dominated by the combination of middle-to-large sized pores with fine-to-coarse throats. Finally, the radius of the throats is in good exponential correlation with permeability and the seepage capacity comes from those large sized throats.
基金supported by the State Key Laboratory of Astronautic Dynamics (2011ADL-DW0202)
文摘Chang＇e-2, Chinese second lunar probe, was inserted into a 100 km altitude low lunar orbit on October 9th, 2010, its purpose is to continuously photograph the lunar surface and possibly chosen landing sites for future lunar missions. The probe will still carry considerable amount of propellant after completing all prescribed tasks in about six months. After the successful launch of Chang＇e-2, we began designing the probe＇s subsequent flight scenario, considering a total impulse of 1 100 m/s for takeoff from low lunar orbit and a maximum 3× 10^6 km distance for Earth-probe telecom- munication. Our first-round effort proposed a preliminary flight scenario that involves consecutive arrivals at the halo orbits around the Earth-Moon L1/L2 and Sun-Earth L1/L2 points, near-Earth asteroid flyby, Earth return, and lunar impact. The designed solution of Chang＇e-2＇s subsequent flight scenario is a multi-segment flight trajectory that serves as a reference for making the final decision on Chang＇e-2＇s extended mission, which is a flight to the Sun-Earth L2 point, and a possible scheme of lunar impact via Earth flyby after remaining at the Sun-Earth L2 point was also presented. The proposed flight trajectory, which possesses acceptable solution accuracy for mission analysis, is a novel design that effectively exploits the invariant manifolds in the circular restricted three-body problem and the patched-manifold-conic method.
基金supported by the State Key Laboratory of Astronautic Dynamics(2011ADL-DW0202)
文摘Driven by curiosity about possible flight options for the Chang＇e-2 spacecraft after it remains at the Sun-Earth L2 point, effective approaches were developed for designing preliminary fuel-optimal near-Earth asteroid flyby trajectories. The approaches include the use of modified unstable manifolds, grid search of the manifolds＇ parameters, and a two-impulse maneuver for orbital phase matching and z-axis bias change, and are demonstrated to be effective in asteroid target screening and trajectory optimization. Asteroid flybys are expected to be within a distance of 2 × 10^7 km from the Earth owing to the constrained Earth-spacecraft communication range. In this case, the spacecraft＇s orbital motion is significantly affected by the gravities of both the Sun and the Earth, and therefore, the concept of the ＂he- liocentric oscillating-Kepler orbit＂ is proposed, because the classical orbital elements of the flyby trajectories referenced in the heliocentric inertial frame oscillate significantly with respect to time. The analysis and results presented in this study show that, among the asteroids whose orbits are the most accurately predicted, ＂Toutatis＂, ＂2005 NZ6＂, or ＂2010 CL19＂ might be encountered by Chang＇e-2 in late 2012 or 2013 with total impulses less than 100 rn/s.
基金supported by the National Basic Research Program of China("973" Program)(2012CB720000)the National Natural Science Foundation of China(11102020)the Program for New Century Excellent Talents in University and Beijing Higher Education Young Elite Teacher Project
文摘Shape modeling is fundamental to the analysis of dynamic environment and motion around asteroid. Chang＇E- 2 successfully made a flyby of Asteroid 4179 Toutatis and obtained plenty of high-resolution images during the mis- sion. In this paper, the modeling method and preliminary model of Asteroid Toutatis are discussed. First, the optical images obtained by Chang＇E-2 are analyzed. Terrain and silhouette features in images are described. Then, the modeling method based on previous radar model and preliminary information from optical images is proposed. A preliminary polyhedron model of Asteroid Toutatis is established. Finally, the spherical harmonic coefficients of Asteroid Toutatis based on the polyhedron model are obtained. Some parameters of model are analyzed and compared. Although the model proposed in this paper is only a preliminary model, this work offers a valuable reference for future high-resolution models.
基金Supported by the National Natural Science Foundation of China under Grant No 11704161the Natural Science Foundation of Jiangsu Province under Grant Nos BK20170309 and BK20151172the Changzhou Science and Technology Bureau under Grant Nos CJ20159049 and CJ20160028
文摘We elucidate the importance of a capping layer on the structural evolution and phase change properties of carbondoped Ge2 Sb2 Te5（C-GST） films during heating in air. Both the C-GST films without and with a thin SiO2 capping layer（C-GST and C-GST/SiO2） are deposited for comparison. Large differences are observed between C-GST and C-GST/SiO2 films in resistance-temperature, x-ray diffraction, x-ray photoelectron spectroscopy,Raman spectra, data retention capability and optical band gap measurements. In the C-GST film, resistancetemperature measurement reveals an unusual smooth decrease in resistance above 110℃ during heating. Xray diffraction result has excluded the possibility of phase change in the C-GST film below 170℃. The x-ray photoelectron spectroscopy experimental result reveals the evolution of Te chemical valence because of the carbon oxidation during heating. Raman spectra further demonstrate that phase changes from an amorphous state to the hexagonal state occur directly during heating in the C-GST film. The quite smooth decrease in resistance is believed to be related with the formation of Te-rich GeTe4-n Gen（n = 0, 1） units above 110℃ in the C-GST film. The oxidation of carbon is harmful to the C-GST phase change properties.
基金funded by the Key Program of National Natural Science Foundation of China (Grant no. 41531069)the Chinese Polar Environment Comprehensive Investigation and Assessment Programs (Grant no. CHINARE2016-02-02)
文摘This study examined the mass change of the Antarctic ice sheet(AIS) based on ICESat and CryoSat-2 observations. We estimated the AIS exhibited mass losses of-101±15 Gt·aduring the ICESat period(Sept–Nov 2003 to Sept–Oct 2009) and-186±55 Gt·aduring the CryoSat-2 period(Jan 2011 to Dec 2015). Mass losses occurred mainly in the sectors of the Amundsen and Bellingshausen seas. Benefitting from the 30-d subcycle of CryoSat-2, we obtained monthly estimates of mass evolution. Considerable annual variations were observed in the mass evolution sequences and the climatological monthly mass evolution. Seasonal mass evolutions in the sectors of the Bellingshausen and Amundsen seas were found most representative of the annual variation. The geographical distribution characteristics of interannual AIS mass evolution were revealed by the annual average mass evolution sequences. During Jan 2011 to Dec 2015, the ice sheets in the sectors of the Bellingshausen and Amundsen seas, and the Totten Glacier, experienced increasingly rapid areal mass loss. An area of mass gain with a moderate rate of increase was found between Dronning Maud Land and Enderby Land. Rapid mass accumulation has occurred in a limited area of the Kamb Ice Stream.
