中上扬子地区五峰组沉积环境分析   总被引：4，自引：0，他引：4  

蔡俊  何幼斌  张来  邱子瑶  甘永年 《海洋地质前沿》2010,26(6)

关于中上扬子地区五峰组的沉积环境是深水沉积还是浅水沉积,这两种观点一直存在较大争议,其焦点主要是关于对观音桥段介壳化石的不同认识。在数十年的学术讨论中,双方都试图从不同方面来证明各自的观点,但至今依然没有得到令人非常信服的结论。通过对古生态学、沉积速率、海平面变化、砾屑灰岩成因讨论等方面的综合分析,认为五峰组为深水沉积的观点更为合理。  相似文献   

Triangulated spherical splines for geopotential reconstruction     

M. J. Lai  C. K. Shum  V. Baramidze  P. Wenston 《Journal of Geodesy》2009,83(8):695-708

We present an alternate mathematical technique than contemporary spherical harmonics to approximate the geopotential based on triangulated spherical spline functions, which are smooth piecewise spherical harmonic polynomials over spherical triangulations. The new method is capable of multi-spatial resolution modeling and could thus enhance spatial resolutions for regional gravity field inversion using data from space gravimetry missions such as CHAMP, GRACE or GOCE. First, we propose to use the minimal energy spherical spline interpolation to find a good approximation of the geopotential at the orbital altitude of the satellite. Then we explain how to solve Laplace’s equation on the Earth’s exterior to compute a spherical spline to approximate the geopotential at the Earth’s surface. We propose a domain decomposition technique, which can compute an approximation of the minimal energy spherical spline interpolation on the orbital altitude and a multiple star technique to compute the spherical spline approximation by the collocation method. We prove that the spherical spline constructed by means of the domain decomposition technique converges to the minimal energy spline interpolation. We also prove that the modeled spline geopotential is continuous from the satellite altitude down to the Earth’s surface. We have implemented the two computational algorithms and applied them in a numerical experiment using simulated CHAMP geopotential observations computed at satellite altitude (450 km) assuming EGM96 (n _max = 90) is the truth model. We then validate our approach by comparing the computed geopotential values using the resulting spherical spline model down to the Earth’s surface, with the truth EGM96 values over several study regions. Our numerical evidence demonstrates that the algorithms produce a viable alternative of regional gravity field solution potentially exploiting the full accuracy of data from space gravimetry missions. The major advantage of our method is that it allows us to compute the geopotential over the regions of interest as well as enhancing the spatial resolution commensurable with the characteristics of satellite coverage, which could not be done using a global spherical harmonic representation. The results in this paper are based on the research supported by the National Science Foundation under the grant no. 0327577.  相似文献   

深圳市闪电定位资料误差分析及其优化     

曾庆锋  张其林  赖鑫  徐栋璞  王皓 《气象科技》2015,43(3):530-536

利用场地误差优化模式对深圳地区的地闪定位资料进行优化处理。首先对深圳市闪电定位系统进行简单介绍,然后利用改进的传输线模式对真实地表环境下的闪电辐射电磁场进行计算,以分析深圳市闪电定位系统的场地误差,最后基于定位误差和场地误差模式对闪电定位数据进行定位误差订正。结果表明不同方位角上的不规则地形对继后回击电磁场波形具有不同影响,随着表征地形粗糙程度的高度均方根的增加,电场的峰值下降,波形的上升沿时间增加。同时,电场波形上升沿时间也会随着方位角的变化而变化,这可能会给时间到达法的定位带来一定误差。为了验证该算法的合理性,对该系统覆盖的区域进行了闪电定位数据优化精度的时空分布分析和评估。结果表明这种优化方案是可行的、可靠的,优化后的闪电定位精度明显提高。  相似文献   

柳州夏季一次雨夹冰雹的天气过程分析     

覃艳秋  赖雨薇  刘蕾 《气象研究与应用》2015,36(1)

利用常规地面观测、柳州地面自动站、FY-2C卫星、柳州和河池的多普勒天气雷达观测资料,对2014年7月22日夏季柳州发生的一次短暂的雨夹冰雹天气过程的环境条件和雷达产品特征进行分析,主要结果如下:受副高和台风外围气流影响,柳州全市出现了37℃以上大范围的高温天气,天气尺度和中尺度的上升运动较弱,局地性质的加热作用导致大气的不稳定度加强而诱发对流云系进一步发展造成的;雷达显示的冰雹云的最大基本反射率因子为65d BZ,强回波区面积小;风速的切变和辐合上升运动小,0℃层高度较高,不利于对流系统的发展和维持。  相似文献   

Characteristics of convection and overshooting in RGB and AGB stars     

Xiang-Jun Lai    Yan Li  National Astronomical Observatories/ Yunnan Observatory  Chinese Academy of Sciences  Kunming  China  Key Laboratory for the Structure  Evolution of Celestial Objects  China Graduate University of Chinese Academy of Sciences  Beijing  China. 《中国天文和天体物理学报》2011,(10)

Based on the turbulent convection model (TCM) of Li & Yang, we have studied the characteristics of turbulent convection in the envelopes of 2 and 5M⊙ stars at the red giant branch and asymptotic giant branch phases. The TCM has been successfully applied over the entire convective envelopes, including the convective unstable zone and the overshooting regions. We find that the convective motions become progressively stronger when the stellar models are located farther up along the Hayashi line. In the convect...  相似文献   

A note on the discovery of a 2M_⊙ pulsar     

Xiao-Yu Lai  Ren-Xin Xu School of Physics  State Key Laboratory of Nuclear Physics  Technology  Peking University  Beijing  China 《中国天文和天体物理学报》2011,(6)

It is conventionally thought that the state equation of dense matter softens and thus cannot result in high maximum mass if pulsars are quark stars and that a recently discovered 2M⊙ pulsar (PSR J1614-2230) may make pulsars unlikely to be quark stars. However, this standard point of view would be revisited and updated if quark clustering could occur in cold quark matter because of the strong coupling be- tween quarks at realistic baryon densities in compact stars. It can be argued that the state equation of...  相似文献   

Origin and evolution of oilfield brines from Tertiary strata in western Qaidam Basin: Constraints from <Superscript>87</Superscript>Sr/<Superscript>86</Superscript>Sr, δD, δ<Superscript>18</Superscript>O, δ<Superscript>34</Superscript>S and water chemistry     

Qishun Fan  Haizhou Ma  Zhongping Lai  Hongbing Tan  Tingwei Li 《中国地球化学学报》2010,29(4):446-454

Chemistry of major and minor elements, ⁸⁷Sr/⁸⁶Sr, δD, δ¹⁸O and δ³⁴S of brines were measured from Tertiary strata and Quaternary salt lakes in the western Qaidam Basin. The water chemistry data show that all oilfield brines are CaCl₂ type. They were enriched in Ca²⁺, B³⁺, Li⁺, Sr²⁺, Br⁻, and were depleted in Mg²⁺, SO₄ ²⁻, which indicated that these brines had the characteristics of deeply circulated water. The relationship between δD and δ¹⁸O shows that all data of these brines decline towards the Global Meteoric Water Line (GWL) and Qaidam Meteoric Water Line (QWL), and that the intersection between oilfield brines and Meteoric Water Lines was close to the local spring and fresh water in the piedmont in the western Qaidam Basin. The results suggest that oilfield brines has initially originated from meteoric water, and then might be affected by water-rock metamorphose, because most oilfield brines distribute in the range of metamorphosing water. The ⁸⁷Sr/⁸⁶Sr values of most oilfield brines range from 0.71121 to 0.71194, and was less than that in salt lake water (>0.712), but close to that of halite in the study area. These imply that salt dissolution occurred in the process of migration. In addition, all oilfield brines have obviously much positive δ³⁴S values (ranging from 26.46‰ to 54.57‰) than that of salt lake brines, which was caused by bacterial sulfate reduction resulting in positive shift of δ³⁴S value and depleteed SO₄ ²⁻ in oilfield brines. Combined with water chemical data and δD, δ¹⁸O, ⁸⁷Sr/⁸⁶Sr, δ³⁴S values, we concluded that oilfield brines mainly originate from the deeply circulated meteoric waters, and then are affected by salt dissolution, water-rock metamorphose, sulfate reduction and dolomitization during the process of migration. These processes alter the chemical compositions of oilfield brines and accumulate rich elements (such as B, Li, Sr, Br, K and so on) for sustainable utilization of salt lake resources in the Qaidam Basin.  相似文献   

福建省矿山地质环境现状和防治建议     

赖荣福 《福建地质》2010,29(Z1)

通过总结福建省矿山开采所造成的矿山地质环境主要问题,分析其对矿山及其周围地质环境造成影响并可能诱发的多种地质环境问题及其危害性。根据福建省矿山地质环境治理现状,提出进一步保护和防治矿山地质环境问题的有效措施。  相似文献   

Semisupervised heterogeneous ensemble for ship target discrimination in synthetic aperture radar images     

Yongxu Li  Xudong Lai  Mingwei Wang 《海洋学报(英文版)》2022,41(7):180-192

Ship detection using synthetic aperture radar (SAR) plays an important role in marine applications. The existing methods are capable of quickly obtaining many candidate targets, but numerous non-ship objects may be wrongly detected in complex backgrounds. These non-ship false alarms can be excluded by training discriminators, and the desired accuracy is obtained with enough verified samples. However, the reliable verification of targets in large-scene SAR images still inevitably requires manual interpretation, which is difficult and time consuming. To address this issue, a semisupervised heterogeneous ensemble ship target discrimination method based on a tri-training scheme is proposed to take advantage of the plentiful candidate targets. Specifically, various features commonly used in SAR image target discrimination are extracted, and several acknowledged classification models and their classic variants are investigated. Multiple discriminators are constructed by dividing these features into different groups and pairing them with each model. Then, the performance of all the discriminators is tested, and better discriminators are selected for implementing the semisupervised training process. These strategies enhance the diversity and reliability of the discriminators, and their heterogeneous ensemble makes more correct judgments on candidate targets, which facilitates further positive training. Experimental results demonstrate that the proposed method outperforms traditional tri-training.  相似文献   

Re-assessment of the paleoclimate implications of the Shell Bar in the Qaidam Basin,China     

Steffen Mischke  Zhongping Lai  Chengjun Zhang 《Journal of Paleolimnology》2014,51(2):179-195

The Shell Bar in the Qaidam Basin, China, is a prominent geological feature composed of millions of densely packed Corbicula shells. Since the mid 1980s, it has been regarded as evidence for existence of a large lake during Marine Isotope Stage (MIS) 3 in the presently hyper-arid Qaidam Basin. Early studies suggested the bivalve shells accumulated at the shore of a large lake, whereas more recent work led to the conclusion that the Shell Bar was formed within a deeper water body. Based on our re-assessment of sediments and fossils from the Shell Bar, investigation of exposed fluvio-lacustrine sections upstream of the Shell Bar and study of nearby modern streams, we infer that the Shell Bar represents a stream deposit. Corbicula is a typical stream-dweller around the world. Preservation of Corbicula shells of different sizes, as well as occurrence of many articulated shells, provide evidence against post-mortem transport and accumulation along a lake shore. Additionally, the SE-NW alignment of the Shell Bar is similar to modern intermittent stream beds in its vicinity and corresponds to the present-day slope towards the basin centre further NW, and furthermore, the predominantly sandy sediments also indicate that the Shell Bar was formed in a stream. Abundant ostracod shells in the Shell Bar sediments originated from stream-dwelling species that are abundant in modern streams in the vicinity of the Shell Bar, or in part from fluvio-lacustrine sediments exposed upstream of the Shell Bar, as a result of erosion and re-deposition. Deflation of alluvial fine-grained sediments in the Shell Bar region and protection of the stream deposits by the large and thick-walled Corbicula shells reversed the former channel relief and yielded the modern exposure, which is a prominent morphological feature. Occurrence of Corbicula shells in the Qaidam Basin indicates climate was apparently warmer than present during the formation of the Shell Bar because Corbicula does not live at similar or higher altitudes in the region today. Because the Shell Bar is no longer considered a deposit formed within a lake, its presence does not indicate paleoclimate conditions wetter than today.  相似文献