共查询到20条相似文献，搜索用时 125 毫秒
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对表征频率稳定度的σy(τ)和σz(τ)方法进行了分析比较。以PSRB1 855 0 9计时观测得到的脉冲星时为例 ,用两种方法估计了其频率稳定度。计算结果和分析表明σz(τ)方法更适合于估计脉冲星时间的频率稳定度 相似文献
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该文基于标准化自协方差函数的组合算法计算了阿仑方差、哈达玛方差的重叠和非重叠形式以及改进阿仑方差、时间方差的等效自由度,并用经验公式计算了总方法估计的等效自由度,在此基础上对各种方差估计不同噪声情况下的等效自由度进行了比较分析,得出如下结论,总方法估计的等效自由度大于相应非总方法估计的等效自由度,重叠和非重叠阿仑方差估计的等效自由度大于相应哈达玛方差估计的等效自由度;对非重叠估计而言,噪声的频率越低,其等效自由度越大;而相应的重叠估计和总方法估计与之相反,噪声的频率越高,其等效自由度越大,这也说明重叠估计和相应的总方法估计对高频噪声等效自由度的提高优于低频噪声. 相似文献
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介绍云南和北京天文台射电频谱仪观测到的3个对偶的米波－－微波Ⅲ型爆发，估计了双向电子束起源的频率和高度，3个事件分别揭示了在正向和反向漂移爆发之间的分界频率（约为250，1300和2900MHz),它们指出了一个致密的电子加速源，在这个源中产生了向上和向下两个方向注入的电子束，从这些事例可以表明不同事件的双向电子束的分界频率有一个相当大的范围（250－2900MHz)，而它们的起源范围却是在一个很小的（大约4－100MHz)和不同的频段范围内。最后讨论了日冕磁结构的拓扑范围、电子加速源构造的空间尺度、电子束运动速度和对偶Ⅲ型爆发的产生机制。 相似文献
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太阳射电尖峰辐射(spike)的窄频带是一个具有特征性的参数,不但可从它计算出Spike辐射源区的小尺度结构,而且观测结果与Spike辐射理论可相互验证.我们利用云南天文台0.5 MHz频率分辨率的射电频谱观测资料,作出了230—300MHz频段上单个Spike带宽分布,并由此给出一群Spike源区的最可几尺度为151km,最大源区尺度为830km. 相似文献
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利用VLBI MKIII系统多磁道记录的优点,在1665和1667MHz两个频率上,同时观测活动恒星形成区 W3(OH)的左右圆偏振羟基分子脉泽辐射。发现了三个Zeeman对,由脉泽子源的速度分裂导得磁场约为6mG,我们估计恒星形成区的磁场和氢气体密度有关系B～n~(0.54)。 相似文献
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卫星动力学模型误差是客观存在的事实,动力学模型误差传递到轨道确定算法中构成部分形式未知的模型误差,并且与测量系统自身的系统误差和随机误差耦合在一起形成定轨模型误差,严重影响轨道确定精度.详细推导了存在动力学模型误差的轨道改进方程,对模型中能准确描述的部分建立了参数化模型,对不能准确描述的误差部分,建立了非参数模型.构建了部分线性轨道改进模型,利用二阶段估计法和核函数估计法对模型误差进行拟合估计,并在轨道改进中予以补偿.根据数据深度理论,建立了非参数模型误差的深度加权核估计方法,提高了模型误差估计的抗差性.最后结合天基空间目标监视系统进行了轨道确定仿真实验.实验结果表明,模型误差是影响轨道确定精度的重要因素,核函数估计法可以有效估计定轨中的模型误差,窗宽是提高模型估计精度的重要变量,通过深度加权处理可以明显提高核函数估计的抗差性,提高轨道确定精度. 相似文献
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本文叙述了一台全新的全光学干涉仪，以此干涉仪为基础，就光纤联接的望远镜干涉阵中用拉伸光纤实现光程补偿的方法在国际上首次进行了研究，在对试验结果进行分析，讨论的基础上肯定了该方法的可行性。 相似文献
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The numerical integration of the differential equations describing dynamical systems has been shown in previous papers of this series to be most effectively accomplished by an explicit Taylor series method.In this paper we show that one explicit Taylor series method, developed earlier in this series and which appears to possess a high degree of versatility, yields considerable gains in efficiency over classical single-step and multi-step methods. (In this context efficiency is a measure of the time taken to carry out a calculation of a specific accuracy).For a given accuracy criterion governing the local truncation error (LTE) it is found that the Taylor series method is generallytwice as fast as the classical multi-step method and up totwenty times faster than the classical single-step method. 相似文献
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Variability is one of the extremely observational properties. In the radio bands, variability is caused by the shock in the jet. In this case, emissions increase rapidly following an exponential curve, and then decrease rapidly also in an exponential curve. The variability time scale is important with regard to the physics carrying on in the jet. However, it is not easy to fit the light curve. In this paper, we proposed a method of light curve fitting on a PC machine, in which the theoretical exponential light curve is adopted to the observations using the least regression method. Using this method, anybody can fit the light curve and get the time scale by moving and clicking the mouse. We also used this method to some light curves obtained from the archive and compared our results with those in the literature. 相似文献
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本文提出了多搜索变量的目标函数直接优化法。该方法不涉及目标函数的导数计算,通用性强;同时该方法可控制搜索变量在值域内取值,这在一定程度上保证了解的可靠性。用此方法,本文分析了1984年2月18日太阳边缘环珥的一些Hα谱线,结果表明,本文方法具有收敛半径大,精度高的特点。 相似文献
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A new method for determining various quantities describing the radiation field in an inhomogeneous, plane-parallel atmosphere
is proposed in this two-part paper. The essence of this method is the reduction of the boundary value problems which arise
during the customary statement of various astrophysical problems associated with solving the radiative transfer equations
to initial value problems. Compared to previous attempts in this area, the proposed method is universal and simple. The first
part of this paper deals with one-dimensional media. Scalar, as well as vector–matrix problems relating to the diffusion of
radiation in spectral lines with frequency redistribution are examined. 相似文献
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The periodogram spectral analysis method applicable to equallyspaced time series is discussed, and the method is tested first with a simulated data series. It is confirmed that this method is effective for noisy series. Then, applying this method to the analysis of the light periods of the quasars 3C 279 and 3C 345 as well as the BL Lac objects OJ 287 and ON 231, we obtain their light periods to be 7.14 yr, 10.00 yr, 11.76 yr and 6.80 yr, respectively. These results obtained by periodogram spectral analysis are consistent with those obtained by the Jurkevich method in the literature. We have analyzed the effects of different window functions, and commented on their correct selection in practical applications. 相似文献
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本文对星表系统差的性质进行了讨论，并分析和评估了目前常用的星表系统差计算方法的优、缺点，从而提出了一个新的星表系统差计算方法．同时也提出了星表系统差计算精度的检验标准．最后对用不同方法计算的系统差进行了分析比较．结果表明，新方法的系统差计算精度好于目前常用的解析方法． 相似文献