Multiperiodicity and physical nature of the δ Sct star GSC 2683-3076     

Ai-Ying Zhou  E. Rodríguez  Zong-Li Liu  Bai-Tian Du 《Monthly notices of the Royal Astronomical Society》2001,326(1):317-325

We present the results of a CCD Johnson V and photoelectric Strömgren uvbyβ photometric study of the recently discovered multiperiodic δ Sct star GSC 2683-3076. Our data set mainly consists of 2874 differential measurements in V together with a few data collected into the uvbyβ system. Additional unfiltered CCD measurements were also carried out. A set of seven best-fitting pulsation frequencies representing the light variations of the variable has been detected. The spectral type of the variable is found to be A9V or F0V. Using the uvbyβ indices the following main physical parameters for the variable have been derived: T _eff=7230 K , M _V =1.95 mag , log  g =3.90 , M =1.85 M_⊙ , R =2.30 R_⊙ , ρ =0.16  ρ _⊙ , age =1.0 Gyr , metal abundance [Me/H]=0.16 and distance modulus =8.4 mag . GSC 2683-3076 is found to be a Population I δ Sct star, slightly metal-enriched, evolving on its main-sequence stage. A mixture of radial and non-radial modes seems to be present in the pulsation of this variable. This star is also known as H133 in the young open cluster NGC 6871, however arguments are given that address this star as a non-member of the cluster. The uvbyβ photometry available in the literature for NGC 6871 is also discussed.  相似文献   

Spherical-earth Fréchet sensitivity kernels     

Tarje Nissen-Meyer  F. A. Dahlen  Alexandre Fournier 《Geophysical Journal International》2007,168(3):1051-1066

  相似文献   

Frequency response modelling of seismic waves using finite difference time domain with phase sensitive detection (TD–PSD)     

Kurt T. Nihei  Xiaoye Li 《Geophysical Journal International》2007,169(3):1069-1078

This paper describes an efficient approach for computing the frequency response of seismic waves propagating in 2- and 3-D earth models within which the magnitude and phase are required at many locations. The approach consists of running an explicit finite difference time domain (TD) code with a time harmonic source out to steady-state. The magnitudes and phases at locations in the model are computed using phase sensitive detection (PSD). PSD does not require storage of time-series (unlike a fast Fourier transform), reducing its memory requirements. Additionally, the response from multiple sources can be obtained from a single finite difference run by encoding each source with a different frequency. For 2-D models with many sources, this time domain phase sensitive detection (TD–PSD) approach has a higher arithmetic complexity than direct solution of the finite difference frequency domain (FD) equations using nested dissection re-ordering (FD–ND). The storage requirements for 2-D finite difference TD–PSD are lower than FD–ND. For 3-D finite difference models, TD–PSD has significantly lower arithmetic complexity and storage requirements than FD–ND, and therefore, may prove useful for computing the frequency response of large 3-D earth models.  相似文献   

A fast converging and anti-aliasing algorithm for Green's functions in terms of spherical or cylindrical harmonics     

Rongjiang Wang  Hansheng Wang 《Geophysical Journal International》2007,170(1):239-248

Geophysical observables are generally related to earth structure and source parameters in a complicated non-linear way. Consequently, a large number of forward modelling processes are commonly necessary to obtain a satisfactory estimate of such parameters from observed data. The most time-consuming part of the forward modelling is the computation of the Green's functions of the different earth models to be tested. In this study, we present a fast converging algorithm: the differential transform method for the computation of Green's functions in terms of spherical or cylindrical harmonics. In this method, a deconvolutable high-pass filter is used to enhance the numerical significance of the far-field spectrum of Green's functions. Compared with existing fast converging algorithms such as the Kummer's transformation and the disc factor method, the differential transform method is more efficient except for the extremely near-source region. The new method can be used to suppress numerical phases (non-physical seismic signals) associated with the aliasing effect that may arise in synthetic seismograms when the latter are computed from a windowed wavenumber (or slowness) spectrum. The numerical efficiency of the new method is demonstrated via two representative tests.  相似文献   

On the laboratory procedure for processing unconsolidated sediment samples to concentrate subfossil seed and other plant macroremains     

Alwynne B. Beaudoin 《Journal of Paleolimnology》2007,37(2):301-308

Macrofossil analysis is becoming increasingly used as an approach to vegetation history in late Quaternary palaeoenvironmental studies. Macrofossils can be recovered from many terrestrial and lacustrine settings. Although the laboratory techniques are straightforward and are described in outline in several textbooks, the practical details of the extraction procedure are not widely available. This paper provides a detailed breakdown of the steps involved in extracting macroremains from unconsolidated (non-lithified) Quaternary sediments, with reasons for the various steps and practical details of how the extraction is accomplished. It is intended as a “how-to” laboratory manual for students and researchers undertaking macrofossil analysis.  相似文献   

地球物理找水方法概述   总被引：1，自引：1，他引：1  

许小强  程顺有 《地下水》2007,29(3):28-29

水是人民生活、经济发展必需的宝贵资源,寻找地下水已是当务之急.文章简要介绍了当前找水使用的各种地球物理方法,重点介绍了最新的找水技术NMR的原理和方法特点.  相似文献   

广东省地质灾害预报预警现状与发展对策     

宫清华  黄光庆  杨木壮  郭敏 《中国地质灾害与防治学报》2007,18(1):10-14

广东省脆弱的地质环境和高强度的人类活动决定了该省地质灾害的多发性、广泛性和严重性。地质灾害给全省造成巨大的经济损失和人员伤亡，严重制约着广东省的社会经济发展。为此，该省于2004年7月启动了地质灾害一气象预报预警工作。目前主要的预报方法有现象监测预报、数理统计预报、非线性系统理论预报和地球内外动力耦合方法预报。因预报预警工作刚刚起步，所以还存在着缺乏地质灾害基础信息储备、监测手段落后、研究方法带有局限性等问题。论文针对这一问题提出运用地理信息系统技术建立基础信息数据库，引入遥感和全球定位系统技术方法提高监测能力，将非线性科学、计算机科学及人工智能技术引入地质灾害预报预警工作，以解决目前工作和研究中方法的缺陷。  相似文献   

低频泥石流特征及其预测初步探讨   总被引：4，自引：0，他引：4  

倪化勇  吕学军  刘宇杰  唐业旗 《工程地质学报》2007,15(5):612-620

同高频泥石流相比,低频泥石流更具有潜在危害性。近年来,低频泥石流的暴发给我国山区人们的生命财产安全、经济发展和社会进步以及山区生态环境带来了极大的影响。本文通过对低频泥石流沟实地考察以及对近年来我国暴发的约30例典型低频泥石流资料进行搜集整理,从其隐蔽性、活动性、规模和破坏性以及灾情等方面探讨了低频泥石流的特征;以茶园沟为例,采用灰色灾变预测方法,建立灰色灾变预测模型对其进行预测,经检验预测结果与实际发生年份一致,并且预测出2042年或2043年前后以及2095年或2096年前后茶园沟发生大规模泥石流的可能性较大;最后,针对低频泥石流的特征,提出了相应的防治建议。  相似文献   

综合物探技术在水利工程建设中的应用     

曾来  谭春 《上海国土资源》2007,(3):45-47

介绍了综合物探中几种常用的方法技术,并结合具体实例说明各方法在水利工程建设中的应用效果。结果表明综合物探技术在水利工程中具有较好的应用前景。  相似文献   

三角剪切断层传播褶皱作用理论与应用     

何登发  John Suppe 《地学前缘》2007,14(4):66-73

基底断层在沉积盖层中传播所形成的褶皱形态难以用平行膝折褶皱理论进行解释,这在于两者的流变学性质有很大差异。Erslev提出了三角剪切断层传播褶皱理论,认为下伏断层的脆性强破裂变形为向上变宽的三角形分布式剪切所调节,三角形顶点固定于断层端点。Hardy和Ford拓展了这一理论并成功地建立数字模拟模型,Allmendinger进一步建立与完善了三角剪切的正演模型与反演方法。通过运动学模型预测结果与天然构造观察和相似模拟实验结果的对比分析,以及通过一系列力学模型对运动学模型的检验,三角剪切断层传播褶皱理论被证实并获得了广泛应用。对前陆盆地、克拉通盆地和走滑盆地的基底卷入型构造与走滑或斜向滑动构造,都可以应用三角剪切断层传播褶皱理论来分析变形样式及其分布特征。该理论可以有效地预测隐伏断层的初始破裂点、断层传播量与发育部位,已成功地应用于工程地质与地震灾害预报等方面。  相似文献