一次热带海洋对流云微物理过程的数值模拟

为了理解微物理过程以及次生对流云对热带对流云团发展演变过程的影响,利用二维云分辨模式对2006年1月20日靠近澳大利亚西北部的印度尼西亚暖池附近的一次对流云降水过程进行数值模拟,分析了对流云发展演变不同阶段各种微物理过程的特征,尤其对次生对流的形成以及并合过程进行了深入分析.结果表明:本个例所研究的热带对流云团具有发展...     

华南准静止锋暖区内降水的物理化学特征

介绍了一次华南准静止暖区内降水的物理化学特征的综合观测分析结果。主要有：①暖区内积云降水雨滴浓度不高，但滴径较大，谱型以多峰谱为主；②雨水ｐＨ值较低，平均４．４３，离子成分中ＮＯ３，Ｃｌ，ＳＯ４，ＮＨ＾＋４，Ｎａ＾＋的浓度较高；③本次降水清除了气溶胶总质量的４５％，对Ｃｌ，Ｆ，ＮＯ３的清除率较高；④由于气溶胶中阴离子被雨水清除的效率较高（主要是ＮＯ３）而阳离子的清除率低，致使雨水ｐＨ值下降，这可能     

Refractive Focusing by Interstellar Clouds and the Rapid Polarization Angle Swing in QSO 1150＋812

A very rapid polarization position angle swing of～180°(with a time scale of～6 hours)observed at 2cm in QSO 1150+812(z=1.25)was reported by Kochenov & Gabuzda.This very rare event is difficult to explain.We found a pos- sible interpretation in the framework of a source model consisting of three polarized components,in which two compact polarized components are nearly simultaneously occulted by an interstellar cloud,with consequent focusing-defocusing effects.A spe- cific plasma-lens model is proposed which can reasonably fit the polarized flux density curve with results derived for the two lensed components.Some physical parameters of the plasma-lens and the source components are estimated.The two compact po- larized components are estimated to have brightness temperatures of～6×10~(12)K. Thus a bulk relativistic motion with a Lorentz factor less than 10 is required to meet the inverse-Compton limit.     

物理海洋学家毛汉礼（上）

毛汉礼。一个普普通通的中国留学生，在获得了加里福尼亚大学海洋物理学博士学位后便急不可待地从加里福尼亚赶到洛杉矾买回国的船票。为了这一天，他经过了整整4年的艰辛努力。当这一天来到时，他想起了生养他的祖国：昔日的祖国战争不断，满目疮痕；而今天，中国人站起来了，伟大的祖国在中国共产党的领导下已崛起在世界的东方。此时，他也想起了家乡和亲人。这念头一产生竟是那样的强烈，他无法抑制自己的感情。     

The Effect of Method of Constructing the Mass Distribution on Single Stellar Populations

We use two methods of constructing the initial mass distribution, the traditional way and Monte Carlo simulation, to obtain integrated U - B, B - V, V-R and V-I colours and absorption-line indices denned by the Lick Observatory image dissector scanner (referred to as Lick/IDS), for instantaneous burst solarmetallicity single stellar populations with ages in the range 1-15 Gyr. We find that the evolutionary curves of all colours obtained by the traditional method are smoother than those by Monte Carlo simulation, that the U - B and B - V colours obtained by the two methods agree with one another, while the V - R and V - I colours by the traditional method are bluer than those by Monte Carlo simulation. A comparison of the Lick/IDS absorption-line indices shows that the variations in all the indices by the traditional method are smoother than that for the Monte Carlo simulation, and that all the indices except for TiO1 and TiO2 are consistent with those for the Monte Carlo simulation.     

Time Scales and Tidal Effects in Minor Mergers

We use controlled N-body simulation to investigate the dynamical processes (dynamical friction, tidal truncation, etc.) involved in the merging of small satellites into bigger halos. We confirm the validity of some analytic formulae proposed earlier based on simple arguments. For rigid satellites represented by softened point masses, the merging time scale depends on both the orbital shape and concentration of the satellite. The dependence on orbital ellipticity is roughly a power law, as suggested by Lacey & Cole, and the dependence on satellite concentration is similar to that proposed by White. When merging satellites are represented by non-rigid objects, Tidal effects must be considered. We found that material beyond the tidal radius are stripped off. The decrease in the satellite mass might mean an increase in the merging time scale, but in fact, the merging time is decreased, because the stripped-off material carries away a proportionately larger amount of of orbital energy and angular momentum.     

鱼类生存：人工对抗天然

海水养殖会严重损害野生鱼类的生存——美国夏威夷大学的尼尔·弗雷泽运用基础物理学解释了鱼类养殖的危害：高密度带来了感染，而感染会降低健康水平。对野生鱼类而言，健康水平的降低意味着难以找到食物，难以逃开“敌人的魔掌”，种群的死亡率随之升高；而养殖鱼不但可享用“免费午餐”，还受到人工保护，从而避免了捕食者的威胁。因此，那些被感染的养殖鱼仍然活了下去，