The potentials of gas generation by kerogen in the late period and by crude oil cracking are closely related to the origin of natural gas in the high- to over mature ma- rine area and their exploration perspectives. T...The potentials of gas generation by kerogen in the late period and by crude oil cracking are closely related to the origin of natural gas in the high- to over mature ma- rine area and their exploration perspectives. The carbon structure of kerogens, with different types and at different evolution stages, have been experimentally studied using the high magnetic field solid 13C nuclear magnetic resonance technique in order to determine the oil and gas potential of kerogens. Results show that the contents of gas potential carbon(GPC) of types I, II, III kerogens at the high- to over mature stage are very low, indicating their weak gas-generating capacity and limited gas production; however, the content of oil potential carbon(OPC) of the low mature type I kerogen is much higher, implying that a large amount of crude oil generated during the oil-generating period will be the material for later gas generation by oil cracking. The kinetic experiment of gas generation by crude oil cracking shows that, when the temperature is about 160℃(Ro=1.6%), the crude oil will start to produce large amounts of gas; the temperature range for major gas generation of crude oil is higher than that of the kerogens, and the gas production is 2 to 4 times higher than that of kerogens. The natural gas de- rived from oil cracking (called oil-cracked gas) is much abundant in methyl hexamethylene, which is quite different from the natural gas produced by thermal degradation of kerogens (named kerogen degradation gas) at high- to over mature stage.展开更多
电子回旋共振离子推力器(electron cyclotron resonance ion thruster,ECRIT)离子源内等离子体分布会影响束流引出,而磁场结构决定的ECR区与天线的相对位置共同影响了等离子体分布.在鞘层作用下,等离子体中的离子或电子被加速对壁面产...电子回旋共振离子推力器(electron cyclotron resonance ion thruster,ECRIT)离子源内等离子体分布会影响束流引出,而磁场结构决定的ECR区与天线的相对位置共同影响了等离子体分布.在鞘层作用下,等离子体中的离子或电子被加速对壁面产生溅射,形成壁面离子或电子电流,造成壁面磨损和等离子体损失,因此研究壁面电流与等离子体特征十分重要.为此本文建立2 cm ECRIT的粒子PIC/MCC(particle-in-cell with Monte Carlo collision)仿真模型,数值模拟研究磁场结构对离子源内等离子体与壁面电流特性的影响.计算表明,当ECR区位于天线上游时,等离子体集中在天线上游和内外磁环间,栅极前离子密度最低,故离子源引出束流、磁环端面电流和天线壁面电流较低.ECR区位于天线下游时,天线和栅极上游附近的等离子体密度较高,故离子源引出束流、天线壁面电流和磁环端面电流较高.腔体壁面等离子体分布与电流受磁场影响最小.展开更多
空间推进所用的电子回旋共振离子源(ECRIS)应具有体积小、效率高的特点.本文研究的ECRIS使用永磁体环产生磁场,有效减小了体积,该离子源利用微波在磁场中加热电子,电子与中性气体发生电离碰撞产生等离子体.磁场在微波加热电子的过程中...空间推进所用的电子回旋共振离子源(ECRIS)应具有体积小、效率高的特点.本文研究的ECRIS使用永磁体环产生磁场,有效减小了体积,该离子源利用微波在磁场中加热电子,电子与中性气体发生电离碰撞产生等离子体.磁场在微波加热电子的过程中起关键作用,同时影响离子源内等离子体的约束和输运.通过比较四种磁路结构离子源的离子电流引出特性来研究磁场对10 cm ECRIS性能的影响.实验发现:在使用氩气的条件下,特定结构的离子源可引出160 mA的离子电流,最高推进剂利用率达60%,最小放电损耗为120 W·A^(-1);所有离子源均存在多个工作状态,工作状态在微波功率、气体流量、引出电压变化时会发生突变.离子源发生状态突变时的微波功率、气体流量的大小与离子源内磁体的位置有关.通过比较不同离子源的引出离子束流、放电损耗、气体利用率、工作稳定性的差异,归纳了磁场结构对此种ECRIS引出特性的影响规律,分析了其中的机理.实验结果表明:保持输入微波功率、气体流量、引出电压不变时,增大共振区的范围、减小共振区到栅极的距离,离子源能引出更大的离子电流;减小共振区到微波功率入口、气体入口的距离能降低维持离子源高状态所需的最小微波功率和最小气体流量,提高气体利用率,但会导致放电损耗增大.研究结果有助于深化对此类离子源工作过程的认识,为其设计和性能优化提供参考.展开更多
已有研究发现金星磁尾的太阳风氢离子(H^(+))和金星电离层氧离子(O^(+))存在大尺度涡流结构,该涡流从磁尾望向星球是逆时针的.为了确定该涡流的存在性,利用金星快车等离子体和高能原子分析仪(Analyzer of Space Plasmas and Energetic A...已有研究发现金星磁尾的太阳风氢离子(H^(+))和金星电离层氧离子(O^(+))存在大尺度涡流结构,该涡流从磁尾望向星球是逆时针的.为了确定该涡流的存在性,利用金星快车等离子体和高能原子分析仪(Analyzer of Space Plasmas and Energetic Atoms on Venus, ASPERA-4)的Fedorov矫正数据,分别在金星公转轨道坐标系(VSO)和太阳风电场坐标系(VSE)下对磁尾等离子体流进行了统计分析.结果显示,在VSO和VSE坐标系中都存在太阳风H^(+)和金星O^(+)的顺时针涡流结构.但是从已有的研究结果看,无论等离子体涡流是逆时针还是顺时针,其产生的磁场都与已知磁尾磁场结构不相符;考虑到金星和火星空间环境的相似性及火星磁尾太阳风H^(+)并不存在完整等离子体涡流的情况,认为金星磁尾可能并不存在大尺度等离子体涡流.金星的等离子体特征需要未来更多卫星观测研究.展开更多
A new method for determining the central axial orientation of a two-dimensional coherent magnetic flux rope(MFR)via multipoint analysis of the magnetic-field structure is developed. The method is devised under the fol...A new method for determining the central axial orientation of a two-dimensional coherent magnetic flux rope(MFR)via multipoint analysis of the magnetic-field structure is developed. The method is devised under the following geometrical assumptions:(1) on its cross section, the structure is left-right symmetric;(2) the projected structure velocity is vertical to the line of symmetry. The two conditions can be naturally satisfied for cylindrical MFRs and are expected to be satisfied for MFRs that are flattened within current sheets. The model test demonstrates that, for determining the axial orientation of such structures, the new method is more efficient and reliable than traditional techniques such as minimum-variance analysis of the magnetic field,Grad-Shafranov(GS) reconstruction, and the more recent method based on the cylindrically symmetric assumption. A total of five flux transfer events observed by Cluster are studied using the proposed approach, and the application results indicate that the observed structures, regardless of their actual physical properties, fit the assumed geometrical model well. For these events, the inferred axial orientations are all in excellent agreement with those obtained using the multi-GS reconstruction technique.展开更多
Cluster spacecraft observed an earthward flowing plasmoid along with a travelling compression region （TCR） structure in southern plasma sheet boundary layer （PSBL） at 21：09 UT of September 19, 2001. We have recon...Cluster spacecraft observed an earthward flowing plasmoid along with a travelling compression region （TCR） structure in southern plasma sheet boundary layer （PSBL） at 21：09 UT of September 19, 2001. We have reconstructed the two-dimensional topology of the magnetic field structure observed by C1 using Grad-Shafranov reconstruction method. Results show that CI passed through part of a plasmoid, which compressed the lobe magnetic field and formed a TCR. The size of the whole plas- moid structure in X direction is estimated to be about 3 Re. Furthermore, using multi-spacecraft observations, we have found some detailed information about this structure. First, C1 observed bi-streaming electron components, which supports our sug- gestion that the spacecraft passed through closed field lines. Second, a small magnetic field perturbation within this plasmoid accompanied by slight decrease in electron flux suggests that a flux rope core might exist at the center of the plasmoid.展开更多
基金This work was supported by the National 973 Natural Gas Project (Grant No, 2001CB209 100).
文摘The potentials of gas generation by kerogen in the late period and by crude oil cracking are closely related to the origin of natural gas in the high- to over mature ma- rine area and their exploration perspectives. The carbon structure of kerogens, with different types and at different evolution stages, have been experimentally studied using the high magnetic field solid 13C nuclear magnetic resonance technique in order to determine the oil and gas potential of kerogens. Results show that the contents of gas potential carbon(GPC) of types I, II, III kerogens at the high- to over mature stage are very low, indicating their weak gas-generating capacity and limited gas production; however, the content of oil potential carbon(OPC) of the low mature type I kerogen is much higher, implying that a large amount of crude oil generated during the oil-generating period will be the material for later gas generation by oil cracking. The kinetic experiment of gas generation by crude oil cracking shows that, when the temperature is about 160℃(Ro=1.6%), the crude oil will start to produce large amounts of gas; the temperature range for major gas generation of crude oil is higher than that of the kerogens, and the gas production is 2 to 4 times higher than that of kerogens. The natural gas de- rived from oil cracking (called oil-cracked gas) is much abundant in methyl hexamethylene, which is quite different from the natural gas produced by thermal degradation of kerogens (named kerogen degradation gas) at high- to over mature stage.
文摘电子回旋共振离子推力器(electron cyclotron resonance ion thruster,ECRIT)离子源内等离子体分布会影响束流引出,而磁场结构决定的ECR区与天线的相对位置共同影响了等离子体分布.在鞘层作用下,等离子体中的离子或电子被加速对壁面产生溅射,形成壁面离子或电子电流,造成壁面磨损和等离子体损失,因此研究壁面电流与等离子体特征十分重要.为此本文建立2 cm ECRIT的粒子PIC/MCC(particle-in-cell with Monte Carlo collision)仿真模型,数值模拟研究磁场结构对离子源内等离子体与壁面电流特性的影响.计算表明,当ECR区位于天线上游时,等离子体集中在天线上游和内外磁环间,栅极前离子密度最低,故离子源引出束流、磁环端面电流和天线壁面电流较低.ECR区位于天线下游时,天线和栅极上游附近的等离子体密度较高,故离子源引出束流、天线壁面电流和磁环端面电流较高.腔体壁面等离子体分布与电流受磁场影响最小.
基金美国太空总署(NASA)支持Smithsonian Astrophysical Observatory的研究基金NAG5-11420美国空军科研办公室(Air Force Office of ScientificResearch)支持Mount Wilson Observatory的研究基金 AF49620-02-1-0194所资助.
文摘空间推进所用的电子回旋共振离子源(ECRIS)应具有体积小、效率高的特点.本文研究的ECRIS使用永磁体环产生磁场,有效减小了体积,该离子源利用微波在磁场中加热电子,电子与中性气体发生电离碰撞产生等离子体.磁场在微波加热电子的过程中起关键作用,同时影响离子源内等离子体的约束和输运.通过比较四种磁路结构离子源的离子电流引出特性来研究磁场对10 cm ECRIS性能的影响.实验发现:在使用氩气的条件下,特定结构的离子源可引出160 mA的离子电流,最高推进剂利用率达60%,最小放电损耗为120 W·A^(-1);所有离子源均存在多个工作状态,工作状态在微波功率、气体流量、引出电压变化时会发生突变.离子源发生状态突变时的微波功率、气体流量的大小与离子源内磁体的位置有关.通过比较不同离子源的引出离子束流、放电损耗、气体利用率、工作稳定性的差异,归纳了磁场结构对此种ECRIS引出特性的影响规律,分析了其中的机理.实验结果表明:保持输入微波功率、气体流量、引出电压不变时,增大共振区的范围、减小共振区到栅极的距离,离子源能引出更大的离子电流;减小共振区到微波功率入口、气体入口的距离能降低维持离子源高状态所需的最小微波功率和最小气体流量,提高气体利用率,但会导致放电损耗增大.研究结果有助于深化对此类离子源工作过程的认识,为其设计和性能优化提供参考.
文摘已有研究发现金星磁尾的太阳风氢离子(H^(+))和金星电离层氧离子(O^(+))存在大尺度涡流结构,该涡流从磁尾望向星球是逆时针的.为了确定该涡流的存在性,利用金星快车等离子体和高能原子分析仪(Analyzer of Space Plasmas and Energetic Atoms on Venus, ASPERA-4)的Fedorov矫正数据,分别在金星公转轨道坐标系(VSO)和太阳风电场坐标系(VSE)下对磁尾等离子体流进行了统计分析.结果显示,在VSO和VSE坐标系中都存在太阳风H^(+)和金星O^(+)的顺时针涡流结构.但是从已有的研究结果看,无论等离子体涡流是逆时针还是顺时针,其产生的磁场都与已知磁尾磁场结构不相符;考虑到金星和火星空间环境的相似性及火星磁尾太阳风H^(+)并不存在完整等离子体涡流的情况,认为金星磁尾可能并不存在大尺度等离子体涡流.金星的等离子体特征需要未来更多卫星观测研究.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40774081, 41231066)Ministry of Science and Technology of China (Grant No. 2011CB811404)the Specialized Research Fund for State Key Laboratories
文摘A new method for determining the central axial orientation of a two-dimensional coherent magnetic flux rope(MFR)via multipoint analysis of the magnetic-field structure is developed. The method is devised under the following geometrical assumptions:(1) on its cross section, the structure is left-right symmetric;(2) the projected structure velocity is vertical to the line of symmetry. The two conditions can be naturally satisfied for cylindrical MFRs and are expected to be satisfied for MFRs that are flattened within current sheets. The model test demonstrates that, for determining the axial orientation of such structures, the new method is more efficient and reliable than traditional techniques such as minimum-variance analysis of the magnetic field,Grad-Shafranov(GS) reconstruction, and the more recent method based on the cylindrically symmetric assumption. A total of five flux transfer events observed by Cluster are studied using the proposed approach, and the application results indicate that the observed structures, regardless of their actual physical properties, fit the assumed geometrical model well. For these events, the inferred axial orientations are all in excellent agreement with those obtained using the multi-GS reconstruction technique.
基金supported by the National Natural Science Foundation of China(Grant No.375 41150110579)the Research Funding Project Thales/HNSWRN,NSRF(Grant No.339868)
文摘Cluster spacecraft observed an earthward flowing plasmoid along with a travelling compression region （TCR） structure in southern plasma sheet boundary layer （PSBL） at 21：09 UT of September 19, 2001. We have reconstructed the two-dimensional topology of the magnetic field structure observed by C1 using Grad-Shafranov reconstruction method. Results show that CI passed through part of a plasmoid, which compressed the lobe magnetic field and formed a TCR. The size of the whole plas- moid structure in X direction is estimated to be about 3 Re. Furthermore, using multi-spacecraft observations, we have found some detailed information about this structure. First, C1 observed bi-streaming electron components, which supports our sug- gestion that the spacecraft passed through closed field lines. Second, a small magnetic field perturbation within this plasmoid accompanied by slight decrease in electron flux suggests that a flux rope core might exist at the center of the plasmoid.
