A simple model for H2 line profiles in bow shocks

We present a model for empirically reproducing line profiles of molecular hydrogen emission in bow shocks. The model takes into account bow velocity, dissociation limit, a cooling function, viewing angle, bow shape and a limited form of extinction. Our results show that both geometrical factors and shock physics can significantly affect the profile morphology. In a companion paper we will apply this model to Fabry–Perot observations of bow shocks in the Orion BN–KL outflow.     

Hydrodynamic Evolution of GRB Afterglow

1 INTRODUCTIONMom the detection at X-rap optical and radio wavelengths of ganuna-ray bursts (GRBs)since 1997 (Costa et al. 1997; van Paradijs et al. 1997; Sahu et al. 1997; Djorgovsld et al. 1997;Metzger et al. 1997; Frail et al. 1997; Taylor et al. 1997; Kulforni et al. 1998; Halpern et al.1998; Castro-Tirado et al. 1999; Kulkalni et al. 1999; Galama et al. 1999), we have come toknow that the GRBs can release 1051 ~ 1054 ergs in a few seconds and that the fireball modelcan describ…     

多方气体球引力坍缩中激波的形成和传播

本文采用计算流体力学中的高分辨率ＰＰＭ格式，数值模拟了多方气体球的引力坍缩、激波形成和传播，物态方程取成Ｐ＝Ｋ（ｓ）ργ，γ为密度的分段函数，通过绝热指数γ的不同取法对三个模型分别进行了计算，并对引力坍缩、反弹激波形成和传播等三个过程以及不同模型之间计算结果上的一些差异做了比较仔细的分析，得到了一些初步结论。     

Ideal MHD simulation of collisionless shockwave

The system of 1-D ideal MHD equations is numerically solved using the WENO scheme. We then simulated the interplanetary collisionless shock wave and investigated the interaction between the perpendicular collisionless shock wave and two kinds of interplanetary structures, structures with opposite magnetic fields and high-density plasmoids. The results are compared with those of particle simulation: they are found to be very similar. For most phenomena concerned with collisionless shock waves, the ideal MHD simulation is accurate and feasible. Moreover, it has a high computational efficiency and is readily extended to the 2-D or 3-D case.     

Limit shocks of relativistic magnetohydrodynamics

In this paper we show that switch-on and switch-off shocks are allowed by the shock equations of relativistic MHD and have similar properties to their Newtonian counterparts. Just like in Newtonian MHD they are limits of fast and slow shock solutions and as such they may be classified as weakly evolutionary shocks.     

Lunar surface electric potential changes associated with traversals through the Earth's foreshock

We report an analysis of one year of Suprathermal Ion Detector Experiment (SIDE) Total Ion Detector (TID) “resonance” events observed between January 1972 and January 1973. The study includes only those events during which upstream solar wind conditions were readily available. The analysis shows that these events are associated with lunar traversals through the dawn flank of the terrestrial magnetospheric bow shock. We propose that the events result from an increase in lunar surface electric potential effected by secondary electron emission due to primary electrons in the Earth's foreshock region (although primary ions may play a role as well). This work establishes (1) the lunar surface potential changes as the Moon moves through the terrestrial bow shock, (2) the lunar surface achieves potentials in the upstream foreshock region that differ from those in the downstream magnetosheath region, (3) these differences can be explained by the presence of energetic electron beams in the upstream foreshock region and (4) if this explanation is correct, the location of the Moon with respect to the terrestrial bow shock influences lunar surface potential.     

A new weir surface repair layer with shock absorbing cushion design

A shock absorbing cushion has never been introduced into any traditional weir surface repair layer design.However,shocks induced by high discharge with heavy sediment can easily produce brittle fracture and peeling over a weir surface repair layer as it is impacted by floods accompanied by particles of different sizes.In this study,transcending traditional designs,the authors developed a composite unit designed with a shock absorbing cushion that has performed well during field tests,proving that the weir body can be effectively protected even if the composite units are directly laid on a severely uneven weir surface repair layer.     

φ178 mm减震器在东北工区的试验应用

东北工区松辽盆地东南隆起的地层多为中生界白垩系地层。登娄库组中上部以上地层可钻性好,机械钻速高;登娄库组中部以下地层可钻性逐渐变差,砂岩致密,泥岩坚硬,钻进中跳钻特别频繁并且严重,转盘转速越高跳钻越严重,对钻头、钻具、设备等使用影响很大。通过试验使用减震器,减小了跳钻的影响,机械钻速平均提高了21%,钻井周期平均缩短了1.27天,使钻井综合成本有了一定幅度的降低,并且大大减轻了对设备、钻具所产生的潜在危害和影响。