信号的瞬时参数与正交小波基   总被引：12，自引：3，他引：9       下载免费PDF全文

李世雄  汪继文 《地球物理学报》2000,43(1):98-104

对于可表成ｕ（ｔ）＝ａ（ｔ）ｃｏｓθ（ｔ）的信号,称ａ（ｔ）为其瞬时振幅,θ（ｔ）为瞬时位相,为瞬时频率．在许多实际问题中,瞬时振幅、位相、频率等瞬时参数的提取有重要意义．但已知的一些瞬时参数计算方法均各有其局限性．本文构造了一种频谱支集紧且有解析表达式的小波,利用它得到一种计算信号瞬时参数的能抗噪声干扰的快速、局部算法．理论分析和数值模拟的结果表明,该方法是实用而有效的,可望能满足许多实际问题的需要．  相似文献   

强夯法加固地基在青岛海关H986工程中的应用     

范先利  赵新宇 《海岸工程》2000,19(1):32-35

重点介绍了在青岛海关Ｈ９８６工程中,对滨海浅滩近期回填的杂填土地基的强夯方法,并对施工中的一些问题予以分析,给出了处理办法。  相似文献   

The region of Collinder 121     

N. T. Kaltcheva 《Monthly notices of the Royal Astronomical Society》2000,318(4):1023-1035

The distribution of bright B-type stars in a field with a radius of 5° centred at the Galactic open cluster Cr 121 is studied utilizing Strömgren and H β photometry. All PPM stars earlier than spectral type A0 are used, revealing a loose nearby structure at a distance of 660–730 pc, and a compact more distant group, which appears to be a genuine cluster: Cr 121. Based on similar coordinates, distances and positions on the colour–magnitude (CM) and Hertzsprung–Russell (HR) diagrams, 11 photometric cluster members are selected at a mean distance of 1085(±41 standard error) pc. The results are discussed in the light of both classical and Hipparcos points of view.  相似文献   

The role of magnetic buoyancy in a Babcock-Leighton type solar dynamo     

Dibyendu Nandy  Arnab Rai Choudhuri 《Journal of Astrophysics and Astronomy》2000,21(3-4):381-385

We study the effects of incorporating magnetic buoyancy in a model of the solar dynamo—which draws inspiration from the Babcock-Leighton idea of surface processes generating the poloidal field. We present our main results here.  相似文献   

中等贫金属星的元素丰度分析     

邱红梅  赵刚  新宇  李宗伟 《中国天文和天体物理学报》2000,20(4)

给出 １１颗中等贫金属星－１．３ ５［Ｆｅ／Ｈ］ ≤－０．６的观测资料,确定了这些样本星的恒星大气参数,得到了这些星中１４种元素的丰度．讨论了各类元素丰度比随金属丰度的变化。α元素（Ｍｇ、 Ｓｉ、 Ｃａ、 Ｔｉ）相对于铁均表现超丰,每一金属丰度处都存在不同程度的弥散．大部分的铁峰元素（Ｖ、Ｃｒ、Ｎｉ、Ｃｕ）也相对于铁超丰,不随［Ｆｅ／Ｈ］而变化,而［Ｍｎ／Ｆｅ］则随金属丰度的增加而增加．［Ｎａ／Ａｌ］在［Ｆｅ／Ｈ］＞－１．１的样本星中表现超车,在［Ｆｅ／Ｈ］＜－１．１的样本中却明显过贫．  相似文献   

低纬子午环方位定向误差及其检测     

铁琼仙  王晓彬 《天文研究与技术》2000,(4)

本文分析了低纬子午环方位定向的误差来源和设置方位检测系统的必要性 ,给出了检测系统的参数 ,用实测值计算了钢球定位盘的精度和用检测值作修正的精度 ,这种修正精度是仅依靠提高仪器稳定性和加工精度所不能达到的 ,文中还叙述了检测系统存在的问题和改进方法。  相似文献   

Boltzmann方程的矩形式及旋转慢收缩中子星中心附近的温度特性     

陈次星  张家铝 《天文学报》2000,41(3):243-256

推出中子星在旋转慢塌缩情况下零质量粒子的Ｂｏｌｔｚｍａｎｎ方程及其矩形式,并研究了典型条件下的慢坍缩问题,而且在近热平衡及扩散近似下得到一个可直接研究中子星中心附近温度特性的有用方程：ａＴｃ＾４ｃ－ａＴ＾４＝ｒＨ３０（６Ｎ＾ΦＯ／Ｎｏｅ－ＮｏА＾－１３ｔｓｉｎθ。  相似文献   

Wavelength dependence of angular diameters of M giants: an observational perspective     

A. P. Jacob  T. R. Bedding  J. G. Robertson  M. Scholz 《Monthly notices of the Royal Astronomical Society》2000,312(4):733-746

We discuss the wavelength dependence of angular diameters of M giants from an observational perspective. Observers cannot directly measure an optical-depth radius for a star, despite this being a common theoretical definition. Instead, they can use an interferometer to measure the square of the fringe visibility. We present new plots of the wavelength-dependent centre-to-limb variation (CLV) of intensity of the stellar disc as well as visibility for Mira and non-Mira M giant models. We use the terms 'CLV spectra' and 'visibility spectra' for these plots. We discuss a model-predicted extreme limb-darkening effect (also called the narrow-bright-core effect) in very strong TiO bands which can lead to a misinterpretation of the size of a star in these bands. We find no evidence as yet that this effect occurs in real stars. Our CLV spectra can explain the similarity in visibilities of R Dor (M8IIIe) that have been observed recently, despite the use of two different passbands. We compare several observations with models, and find that the models generally underestimate the observed variation in visibility with wavelength. We present CLV and visibility spectra for a model that is applicable to the M supergiant α Ori.  相似文献   

A spectroscopic study of V603 Aquilae: stellar parameters and continuumline variations     

J. Arenas  M. S. Catalán  T. Augusteijn  A. Retter 《Monthly notices of the Royal Astronomical Society》2000,311(1):135-148

A time-resolved spectroscopic study of V603 Aql (Nova Aquilae 1918) is presented. An orbital period of P _orb=01385±00002, consistent with previous results, and a radial velocity semi-amplitude of K =20±3 km s¹ are obtained from the radial velocity variations of the H emission line. Similar K values are also found in H , H , and He  i emission lines. Using the measured FWHM of the H line and assuming that the derived semi-amplitude is that of the white dwarf, we deduce a most likely mass ratio of q =0.24±0.05 and stellar masses of M ₂=0.29±0.04 M and M ₁=1.2±0.2 M for the secondary and primary (the white dwarf) star, respectively. The dynamical solution also indicates a very low orbital inclination, i =13°±2°. We find that the continuum and line variations are modulated with both the positive and the negative superhump periods, indicating that they arise from similar regions of the accretion disc. Moreover, we find, for the first time from spectroscopy, evidence of negative superhumps in addition to the positive superhumps. Positive superhumps are explained within the disc instability model as caused by an eccentric disc surrounding the white dwarf, which is precessing (apsidal advance) because of tidal instabilities, causing the observed positive superhumps. A nodal precession in the accretion disc is currently believed to be the cause of the observed negative superhumps. The low value of q is consistent with the expected value for systems that show superhumps, in accordance with the eccentric disc model. We find no evidence of periodicity associated with the spin period.  相似文献   

On the accuracy of the measurements of low-ℓ solar acoustic oscillations     

V. G. Gavryusev  E. A. Gavryuseva 《Monthly notices of the Royal Astronomical Society》2000,317(3):569-580

Using a 1154 d long measurement of solar oscillations, obtained by the Global Oscillation Network Group from 1995 June 10 to 1998 August 6, we study the dependence of the accuracy of radial p-mode parameters on the duration of the observations. It is shown that relatively rare pulses of large power lead to the decrease of the accuracy achievable for a given duration of the observations and it is usually underestimated. The corresponding correction factor to the Libbrecht formula for a frequency accuracy estimation is provided. We have also investigated the influence of the solar activity on the mode parameters soon after the solar activity minimum. There is a clearly visible increase of the radial p-mode power in the beginning of the new solar cycle while the mode frequency variations are within the corresponding error bars.  相似文献