Laboratory Experiment of Plasma Flow Around Magnetic Sail     

Ikkoh Funaki  Hidenori Kojima  Hiroshi Yamakawa  Yoshinori Nakayama  Yukio Shimizu 《Astrophysics and Space Science》2007,307(1-3):63-68

To propel a spacecraft in the direction leaving the Sun, a magnetic sail (MagSail) blocks the hypersonic solar wind plasma flow by an artificial magnetic field. In order to simulate the interaction between the solar wind and the artificially deployed magnetic field produced around a magnetic sail spacecraft, a laboratory simulator was designed and constructed inside a space chamber. As a solar wind simulator, a high-power magnetoplasmadynamic arcjet is operated in a quasisteady mode of 0.8 ms duration. It can generate a simulated solar wind that is a high-speed (above 20 km/s), high-density (10¹⁸ m⁻³) hydrogen plasma plume of ∼0.7 m in diameter. A small coil (2 cm in diameter), which is to simulate a magnetic sail spacecraft and can obtain 1.9-T magnetic field strength at its center, was immersed inside the simulated solar wind. Using these devices, the formation of a magnetic cavity (∼8 cm in radius) was observed around the coil, which indicates successful simulation of the plasma flow of a MagSail in the laboratory.  相似文献   

Investigating the Andromeda stream – III. A young shell system in M31     

M. A. Fardal  P. Guhathakurta  A. Babul  A. W. McConnachie 《Monthly notices of the Royal Astronomical Society》2007,380(1):15-32

Published maps of red giant stars in the halo region of M31 exhibit a giant stellar stream to the south of this galaxy, as well as a giant 'shelf' to the northeast of M31's centre. Using these maps, we find that there is a fainter shelf of comparable size on the western side as well. By choosing appropriate structural and orbital parameters for an accreting dwarf satellite within the accurate M31 potential model of Geehan et al., we produce a very similar structure in an N -body simulation. In this scenario, the tidal stream produced at pericentre of the satellite's orbit matches the observed southern stream, while the forward continuation of this tidal stream makes up two orbital loops, broadened into fan-like structures by successive pericentric passages; these loops correspond to the north-eastern and western shelves. The tidal debris from the satellite also reproduces a previously observed 'stream' of counterrotating planetary nebulae and a related stream seen in red giant stars. The debris pattern in our simulation resembles the shell systems detected around many elliptical galaxies, though this is the first identification of a shell system in a spiral galaxy and the first in any galaxy close enough to allow measurements of stellar velocities and relative distances. We discuss the physics of these partial shells, highlighting the role played by spatial and velocity caustics in the observations. We show that kinematic surveys of the tidal debris will provide a sensitive measurement of M31's halo potential, while quantifying the surface density of debris in the shelves will let us reconstruct the original mass and time of disruption of the progenitor satellite.  相似文献   

不同悬沙组分对潮流的响应关系研究     

朱子晨  胡泽建  刘建强  张莞君  张永强  黄炳智 《海洋科学进展》2020,38(1):103-112

通过建立一维水深平均悬沙模型,对典型潮流控制的海湾内不同悬沙组分对潮流的响应关系进行了研究。模型以泥沙的水平输运、再悬浮和沉降为主要物理过程,以M2,S2分潮及余流为主要动力因素,反演了湄洲湾支水道内粉砂、淤泥组分含量的时间序列,采用2007-08潮位、潮流、悬沙、底质同步观测资料进行分析和验证。通过三角傅里叶分析,将悬沙的时间序列分解为12个主要的谐波分量,模型分解得到的主要傅里叶分量具有M2分潮两倍的角速度与1/4日潮周期,该分量粉砂组分振幅6.1 mg/L,淤泥组分振幅1.5 mg/L;次主要傅里叶分量具有M2分潮的角速度,振幅受水平输沙、余流、M2分潮流共同影响,粉砂组分振幅4.9 mg/L,淤泥组分振幅1.2 mg/L。由于粉砂组分单位起动能力强、沉降速度高,且淤泥组分由于粘结力等因素起动条件较高,粉砂组分振幅高于淤泥组分。测站位置余流与涨潮流方向一致,余流致使涨潮过程中粉砂组分含量所占百分比上升,而落潮过程下降,淤泥组分则相反。  相似文献   

2002年玉门5.9级地震序列精确定位和发震构造研究   总被引：2，自引：1，他引：1  

荣代潞  李亚荣 《地震研究》2005,28(3):239-243

用“双差法”对2002年12月14日甘肃玉门5．9级地震的主震和余震序列进行了重新精确定位,在此基础上讨论了本次地震的发震断层和发震机制。结果表明,在汇合处玉门断裂向深部延伸和旱峡一大黄沟断裂汇合在汇合处的断层面上发生逆推错动,造成这次主震和余震的能量释放。  相似文献   

2004年12月26日印尼8.7级地震综述   总被引：8，自引：0，他引：8  

梁凯利 《国际地震动态》2005,(1):1-5

本文给出了2004年12月26日印尼8．7级大地震的基本参数、区域构造背景、地震及海啸的损失情况及各国的应急反应,并提出了一些有益的建议。  相似文献   

谈温州经验及湖北测绘行业的发展     

欧阳光辉  赵喜红 《地理空间信息》2004,2(5):49-50

通过考察和学习温州测绘工作,总结了温州测绘行业管理和生产经营的特点,结合我省实际,借鉴温州测绘经验,探索加速发展湖北测绘行业的新思路。  相似文献   

GQLup and its common proper motion companion     

M. Mugrauer  R. Neuhuser 《Astronomische Nachrichten》2005,326(8):701-708

  相似文献   

水平简谐荷载作用下层状饱和土体动力响应   总被引：1，自引：0，他引：1  

徐满清  金腊华  黎剑华  徐斌  陆建飞 《岩土力学》2009,30(9):2633-2642

根据Biot波动理论,采用传递、反射矩阵（TRM）方法研究了水平简谐荷载作用下层状饱和土动力响应问题。由Helmholtz矢量分解求出基本解,再利用TRM法推导了层状饱和土动力响应,并由数值Hankel逆变换得到层状土地基位移、应力及孔压在空间域内的解。利用计算结果与已有结果相比较,二者相吻合,验证了算法的正确性。算例分析表明,水平简谐荷载作用在有软弱夹层的层状土体中比均质土中具有更显著的动力响应,尤其是软夹层上下有硬土层时,会引起软弱夹层土体孔隙水压升高、位移幅值增大、土体波动性增强;而荷载作用硬夹层及夹层上下有软土层时,情况则相反。  相似文献   

上海浦东国际机场建设中的测绘新技术应用     

林正庆  朱妙珍 《测绘工程》2000,9(4):37-39

介绍了上海市浦东国际机场建设中测绘新技术的应用,为加快建立上海市城市系统和机场系统的地理信息数据库作出重要的保障,使机场运行后实施更科学更现代化的管理．  相似文献   

Cosmic ray generation by quasar remnants: constraints and implications     

Elihu Boldt  Michael Loewenstein 《Monthly notices of the Royal Astronomical Society》2000,316(3):L29-L33

We report the first detection of CO in the bulge of M31. The ¹²CO (1–0) and (2–1) lines are both detected in the dust complex D395A/393/384, at 1.3 arcmin (∼0.35 kpc) from the centre. From these data and from visual extinction data, we derive a CO luminosity to reddening ratio (and a CO luminosity to H₂ column density ratio) quite similar to that observed in the local Galactic clouds. The (2–1) to (1–0) line intensity ratio points to a CO rotational temperature and a gas kinetic temperature of >10 K. The molecular mass of the complex, inside a 25-arcsec (100 pc) region, is 1.5×10⁴ M_⊙.  相似文献