用小波方法分析2000年7月13日地磁扰动

利用MORLET小波变换对2000年7月13日亚暴期间地磁场变化特征进行了分析。通过小波分析可以得到亚暴增长相、膨胀相,恢复相的发展过程．探讨了亚暴期间地磁脉动的特征。从小波谱中得到,一个谱结构是处于最高纬度的NAL台站更早出现较大的谱值,这说明此次事件中,地磁场首先在高纬区响应行星际扰动。另一个有明显谱结构的周期在：320～2000s之间,该周期范围的波谱几乎分布一天中的各个时段,但在1000～1700UT亚暴期间之间频带变宽并明显增强,这表明亚暴爆发将引起地磁场在高频端的强扰动。     

岩溶空腔水气压力脉动效应的发现及意义

通过塌陷的地质模式概化,设计物理模型实验探索岩溶空腔在开放、密闭条件下,地下水位下降时水气压力变化的规律。实验结果表明:（1）在密闭条件下水位下降时,空腔内的水气压力处于负压状态,并呈有规律的波动, 波动周期和幅度主要受初始水位的影响;（2）在密封-开放-密封实验中,当系统突然转为开放条件时,岩溶空腔内的水气压力发生突变,压力突变值可达密闭系统条件下最大波动值的3倍;（3）岩溶空腔水位下降过程中,水气压力对岩溶空腔顶部有周期性的高频振动作用,具有压力脉动的特征;（4）密闭条件下的岩溶空腔水位下降引起的水气压力变化可通过时间变量的一次函数来描述,函数斜率受出水口及岩溶空腔截面积影响,截距与初始水位紧密相关。对水气压力所产生的高频振动特征进行深入研究,将有助于岩溶塌陷机理及防治研究的突破。      

地脉动特征波形自动分析方法

地脉动特征波形自动分析主要是应用数学计算软件MATLAB对特征波形数据进行量化分析、统计、计算,并应用MATLAB语言编写相应程序对特征波形进行数学方法处理、特征波形自动拾取、波形幅频分析,自动生成相关数据文件和结果图形,以便对地脉动特征规律做进一步分析。     

基于唐山7.8级地震探讨动态应力作用

运用三维非线性动态有限元方法(Non-linear Dynamic FEM)仿真模拟研究了菱形模型的动态应力作用,分析了1976年唐山7.8级地震.结果表明:(1)唐山地震前增强的中强地震产生的冲击力形成的应力波反射后发生半波损失, 成为动态的拉伸应力,通过减小内摩擦而引起岩石产生裂纹、局部破裂并发生串通,一方面触发地震,另一方面为孕育唐山地震积累能量,表现为正反馈过程.(2)唐山地震产生的冲击力加卸载存在时间差,造成加卸载冲击波相位不同,结果产生的动应力和围压叠加致使围压波动和下降,导致抗剪切强度降低,使初始破裂分别向北东、西南方向传播.(3)冲击力的卸载,相对于产生拉伸性的应力波,反射后发生半波损失,成为动态的压缩应力,致使围压增大并导致破裂停止;而动态应力在传播过程中衰减.因此,余震的发生是一个负反馈过程.     

Modelling the Planetary Nebula

Deep narrow-band imaging and spectroscopy of the Planetary Nebula (PN)surrounding V4334 Sagittarii have been obtained since the onset of thethermal pulse in the star. Although of low surface brightness,narrow-band imaging suggests a ring structure maybepresent. Abundances, expansion rates and physical parameters for thenebula, derived from spectroscopy, show the plasma to be essentiallytypical of old evolved PN (within the errors of observation). The mostrecent data show little evidence of recombination indicating a verylow plasma electron density.Assuming no recombination has occurred, models of the PN spectrum wereconstructed using both simplistic ideas as well as sophisticatedphoto-ionisation codes. These show good agreement, and suggest that thepre-outburst UV radiation field would need to be powered by aprecursor with a surface temperature of T > 10⁵K. The luminosity ofthis star is less well constrained by the models, and cannot be usedsolely to accurately determine its distance. However, by excludingunrealistic models we expect 250 > L/L_odot > 1000 or so. When plotted ona HR diagram for evolved stars this shows good agreement with thatexpected for a pre-last thermal pulse object.     

Higher order resonant orbits

I present higher-order resonances of the tube and boomerang orbits in the co-rotating meridional plane of an axisymmetric galactic potential. Additionally, mirror forms of these orbits are given.     

PSDF: Particle Stream Data Format for N-body simulations

We present a data format for the output of general N-body simulations, allowing the presence of individual time steps. By specifying a standard, different N-body integrators and different visualization and analysis programs can all share the simulation data, independent of the type of programs used to produce the data. Our Particle Stream Data Format, PSDF, is specified in YAML, based on the same approach as XML but with a simpler syntax. Together with a specification of PSDF, we provide background and motivation, as well as specific examples in a variety of computer languages. We also offer a web site from which these examples can be retrieved, in order to make it easy to augment existing codes in order to give them the option to produce PSDF output.     

Consequences of clumping in hot-star winds

It seems more and more likely that one will have to abandon the paradigm of smooth outflows from (hot) stars in favour of a clumpy structure, possibly in a fractal-like hierarchy on all scales. Observationally, this is best established for Wolf-Rayet star winds (e.g. scaling laws, mass-spectrum, anisotropy,...), for which the consequences of clumping are discussed. These include four broad categories, which are outlined in this review: (a) an ideal laboratory for studying time-dependent astrophysical turbulence, (b) potential tracers of hot-wind global structure parameters, (c) reduced mass-loss rates, and (d) impact on massive binary studies.     

银河系疏散星团中的蓝离散星(英文)

作为目前研究复杂恒星系统的有力工具 ,星族合成方法是建立在单星演化理论基础之上的 ,因此 ,必然有其不完善性存在 ,尤其当系统中的双星成分不容忽视时。作为演化星族合成方法的基本单元 ,简单恒星星族模型的构成即排除了双星贡献。本文中 ,我们以银河系疏散星团为简单恒星星族模板 ,构造出一系列简单恒星星族积分光谱。从中我们可以看到 :蓝离散星这类理论上主要来源于双星系统的恒星 ,对星团积分光谱的紫外及蓝端有很大影响 ,从而造成简单恒星星族积分光谱能量分布的改变。这种改变势必影响对星团年龄及其它一些物理参量的判定 ,并最终影响星族合成的结果。同时 ,若以 (B -V )色指数进行度量 ,蓝离散星对简单恒星星族积分颜色的影响可达到 30 %。工作中 ,我们选取了 2 6个年龄在1x10 1 0 ～ 6x10 1 0 年之间的疏散星团为样本进行统计研究。