中国红层的分布及地质环境特征   总被引：47，自引：3，他引：44  

程强寇小兵  黄绍槟周永江 《工程地质学报》2004,12(1):34-40

根据我国红层的分布特征及形成背景 ,将我国红层划分为西南地区红层、西北地区红层、中南、东南地区红层和其他地区 (西藏及华北的部分地区 )红层。重点研究了以川滇红层为代表的西南地区红层和以甘肃红层为代表的西北地区红层 ,研究了各个区域红层的地质构造特征、地形地貌特征、气候环境特征等工程地质环境特征 ,根据工程地质环境特征 ,将研究区域的红层划分为四川盆地红层、西昌滇中红层、滇西红层和甘肃红层.  相似文献   

应用多元素背景判别法在浅覆盖区进行1:20万地质填图的尝试     

王保林  翁士明  汤正江 《安徽地质》2005,15(4):294-297,309

运用1：20万水系沉积物测量中多种元素的背景含量对浅覆盖区的主要地质体和线形构造进行尝试性划分。通过对区域化探资料的整理分析,依据地球化学示踪作用原理,运用多元素背景判别法,较好地圈定了存在元素含量差的地质体和线性构造,提高浅覆盖区区域地质填图成果的信息承载量。  相似文献   

非洲大陆构造单元划分     

胡鹏  任军平  向鹏  古阿雷  王建雄  王杰  吴大天  向文帅  孙凯  赵凯  刘晓阳  姜军胜  曾威  曾国平  张航  刘江涛  周佐民 《地质通报》2022,(1):1-18

非洲大陆地质演化历史悠久,矿产资源丰富.综合已有研究成果,对非洲大陆地质背景、构造单元划分及主要构造单元特征进行简要总结.非洲大陆跨特提斯和冈瓦纳两大构造域,大部分属于冈瓦纳构造域,主要由太古宙—古元古代结晶基底、上覆盖层和泛非构造带组成.根据非洲大陆地质背景和构造演化,在前人研究的基础上,将非洲大陆划分为2个一级构造...  相似文献   

环境变化对信阳测震台背景噪声水平的影响   总被引：1，自引：1，他引：0  

杨龙翔  孙杰  王志铄  贾漯昭  韩艳杰  阎楷 《地震地磁观测与研究》2014,35(5)

利用均方根速度值计算方法及背景噪声功率谱概率密度函数方法,对信阳测震台20082013年数据进行计算,得到不同时期背景噪声水平,分析环境变化对背景噪声的影响.  相似文献   

Foreground removal from Planck Sky Model temperature maps using a MLP neural network     

H.U. Nrgaard‐Nielsen  K. Hebert 《Astronomische Nachrichten》2009,330(8):863-870

Unfortunately, the Cosmic Microwave Background (CMB) radiation is contaminated by emission originating in the Milky Way (synchrotron, free‐free and dust emission). Since the cosmological information is statistically in nature, it is essential to remove this foreground emission and leave the CMB with no systematic errors. To demonstrate the feasibility of a simple multilayer perceptron (MLP) neural network for extracting the CMB temperature signal, we have analyzed a specific data set, namely the Planck Sky Model maps, developed for evaluation of different component separation methods before including them in the Planck data analysis pipeline. It is found that a MLP neural network can provide a CMB map of about 80 % of the sky to a very high degree uncorrelated with the foreground components. Also the derived power spectrum shows little evidence for systematic errors (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Maximum likelihood algorithm for parametric component separation in cosmic microwave background experiments     

Radek Stompor  Samuel Leach  Federico Stivoli  Carlo Baccigalupi 《Monthly notices of the Royal Astronomical Society》2009,392(1):216-232

We discuss an approach to the component separation of microwave, multifrequency sky maps as those typically produced from cosmic microwave background (CMB) anisotropy data sets. The algorithm is based on the two-step, parametric, likelihood-based technique recently elaborated on by Eriksen et al., where the foreground spectral parameters are estimated prior to the actual separation of the components. In contrast with the previous approaches, we accomplish the former task with help of an analytically derived likelihood function for the spectral parameters, which, we show, yields estimates equal to the maximum likelihood values of the full multidimensional data problem. We then use these estimates to perform the second step via the standard, generalized-least-squares-like procedure. We demonstrate that the proposed approach is equivalent to a direct maximization of the full data likelihood, which is recast in a computationally tractable form. We use the corresponding curvature matrices to characterize statistical properties of the recovered parameters. We incorporate in the formalism some of the essential features of the CMB data sets, such as inhomogeneous pixel domain noise, unknown map offsets as well as calibration errors and study their consequences for the separation. We find that the calibration is likely to have a dominant effect on the precision of the spectral parameter determination for a realistic CMB experiment. We apply the algorithm to simulated data and discuss the results. Our focus is on partial sky, total intensity and polarization, CMB experiments such as planned balloon-borne and ground-based efforts, however, the techniques presented here should be also applicable to the full-sky data as for instance, those produced by the Wilkinson Microwave Anisotropy Probe ( WMAP ) satellite and anticipated from the Planck mission.  相似文献   

Phase shift sequences for an adding interferometer     

Peter Hyland †  Brent Follin  Emory F. Bunn 《Monthly notices of the Royal Astronomical Society》2009,393(2):531-537

Cosmic microwave background (CMB) polarimetry has the potential to provide revolutionary advances in cosmology. Future experiments to detect the very weak B-mode signal in CMB polarization maps will require unprecedented sensitivity and control of systematic errors. Bolometric interferometry may provide a way to achieve these goals. In a bolometric interferometer (or other adding interferometer), phase shift sequences are applied to the inputs in order to recover the visibilities. Noise is minimized when the phase shift sequences corresponding to all visibilities are orthogonal. We present a systematic method for finding sequences that produce this orthogonality, approximately minimizing both the length of the time sequence and the number of discrete phase shift values required. When some baselines are geometrically equivalent, we can choose sequences that read out those baselines simultaneously, which has been shown to improve the signal-to-noise ratio.  相似文献   

Impact of Galactic polarized emission on B-mode detection at low multipoles     

G. Efstathiou  S. Gratton  F. Paci 《Monthly notices of the Royal Astronomical Society》2009,397(3):1355-1373

We use a model of polarized Galactic emission developed by the Planck collaboration to assess the impact of foregrounds on B -mode detection at low multipoles. Our main interest is in applications of noisy polarization data and in particular in assessing the feasibility of B -mode detection by Planck . This limits the complexity of foreground subtraction techniques that can be applied to the data. We analyse internal linear combination techniques and show that the offset caused by the dominant E -mode polarization pattern leads to a fundamental limit of   r ∼ 0.1  for the tensor–scalar ratio even in the absence of instrumental noise. We devise a simple, robust, template fitting technique using multifrequency polarization maps. We show that template fitting using Planck data alone offers a feasible way of recovering primordial B -modes from dominant foreground contamination, even in the presence of noise on the data and templates. We implement and test a pixel-based scheme for computing the likelihood function of cosmological parameters at low multipoles that incorporates foreground subtraction of noisy data.  相似文献   

Analysis of non-Gaussian cosmic microwave background maps based on the N-pdf. Application to Wilkinson Microwave Anisotropy Probe data     

P. Vielva  J. L. Sanz 《Monthly notices of the Royal Astronomical Society》2009,397(2):837-848

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Limits on isocurvature perturbations from non-Gaussianity in WMAP temperature anisotropy     

Chiaki Hikage  Kazuya Koyama  Takahiko Matsubara  Tomo Takahashi  Masahide Yamaguchi 《Monthly notices of the Royal Astronomical Society》2009,398(4):2188-2198

We study the effect of primordial isocurvature perturbations on non-Gaussian properties of cosmic microwave background (CMB) temperature anisotropies. We consider generic forms of the non-linearity of isocurvature perturbations which can be applied to a wide range of theoretical models. We derive analytical expressions for the bispectrum and the Minkowski Functionals for CMB temperature fluctuations to describe the non-Gaussianity from isocurvature perturbations. We find that the isocurvature non-Gaussianity in the quadratic isocurvature model, where the isocurvature perturbation S is written as a quadratic function of the Gaussian variable  σ,  S =σ²−〈σ²〉  , can give the same signal-to-noise ratio as   f _NL= 30  even if we impose the current observational limit on the fraction of isocurvature perturbations contained in the primordial power spectrum α. We give constraints on isocurvature non-Gaussianity from Minkowski Functionals using the Wilkinson Microwave Anisotropy Probe ( WMAP ) 5-year data. We do not find a significant signal of isocurvature non-Gaussianity. For the quadratic isocurvature model, we obtain a stringent upper limit on the isocurvature fraction  α < 0.070  (95 per cent CL) for a scale-invariant spectrum which is comparable to the limit obtained from the power spectrum.  相似文献