对化探异常评价的思考

化探异常评价是地质普查找矿中的一项重要工作,异常评价的主要工作环节为异常筛选阶段,异常源追踪,定位阶段和异常起因研究,高质量地完成三个环节的各项工作,除掌握好地球化学本学科的基础理论之外,尚需地质,地球物理等其它多学科的基础理论的支持,尤其是现代成矿理论和地质找矿技术的支持。     

Quantifying and testing differences among means of compositional data suites

Commonly, geological studies compare mean values of two or more compositional data suites in order to determine if, how, and by how much they differ. Simple approaches for evaluating and statistically testing differences in mean values for open data fail for compositional (closed) data. A new parameter, an f-value, therefore has been developed, which correctly quantifies the differences among compositional mean values and allows testing those differences for statistical significance. In general, this parameter quantifies only therelative factor by which compositional variables differ across data suites; however for situations where, arguably, at least one component has neither increased nor decreased, anabsolute f-value can be computed. In situations where the compositional variables have undergone many perturbations, arguments based upon thef-values and the central limit theorem indicate that logratios of compositional variables should be normally distributed.     

基于GNSS的空间环境参数反演平台及精度评估

基于全球和区域全球导航卫星系统（GNSS）参考站网进行对流层和电离层参数反演实现空间环境变化监测具有成本低、精度高、实时性好等优点,得到了广泛应用.本文基于南京信息工程大学的北斗/GNSS空间环境监测平台Xsensing,以国际GNSS服务组织提供的对流层产品为参考,评估了不同气象条件下对流层参数反演精度,在此基础上采用固定非差模糊度的精密单点定位技术（PPP）实现高精度电离层参数反演.实验结果表明,基于全球参考站的对流层估计误差偏差为0.05 mm,对应的标准差为5.6 mm,在平稳和剧烈的气象条件下均能反映水汽变化趋势特征.基于短基线进行电离层延迟反演精度评估,结果表明浮点解PPP反演电离层延迟误差的平均偏差为-0.09 TECU,精度为0.38 TECU,采用非差模糊度固定技术对电离层延迟提取精度提高达84.2％;静态模拟动态解算模式下电离层估计精度与静态相当.上述结果表明该平台可实现高精度空间环境参数反演,下一步将融合机载、船载等多种平台观测实现中小尺度空间变化监测.     

ITG-CHAMP01: a CHAMP gravity field model from short kinematic arcs over a one-year observation period

Global gravity field models have been determined based on kinematic orbits covering an observation period of one year beginning from March 2002. Three different models have been derived up to a maximum degree of n=90 of a spherical harmonic expansion of the gravitational potential. One version, ITG-CHAMP01E, has been regularized beginning from degree n=40 upwards, based on the potential coefficients of the gravity field model EGM96. A second model, ITG-CHAMP01K, has been determined based on Kaulas rule of thumb, also beginning from degree n=40. A third version, ITG-CHAMP01S, has been determined without any regularization. The physical model of the gravity field recovery technique is based on Newtons equation of motion, formulated as a boundary value problem in the form of a Fredholm-type integral equation. The observation equations are formulated in the space domain by dividing the one-year orbit into short sections of approximately 30-minute arcs. For every short arc, a variance factor has been determined by an iterative computation procedure. The three gravity field models have been validated based on various criteria, and demonstrate the quality of not only the gravity field recovery technique but also the kinematically determined orbits.     

Monitoring of seismic events from a specific source region using a single regional array: A case study

In the monitoring of earthquakes and nuclear explosions using a sparse worldwide network of seismic stations, it is frequently necessary to make reliable location estimates using a single seismic array. It is also desirable to screen out routine industrial explosions automatically in order that analyst resources are not wasted upon detections which can, with a high level of confidence, be associated with such a source. The Kovdor mine on the Kola Peninsula of NW Russia is the site of frequent industrial blasts which are well recorded by the ARCES regional seismic array at a distance of approximately 300 km. We describe here an automatic procedure for identifying signals which are likely to result from blasts at the Kovdor mine and, wherever possible, for obtaining single array locations for such events. Carefully calibrated processing parameters were chosen using measurements from confirmed events at the mine over a one-year period for which the operators supplied Ground Truth information. Phase arrival times are estimated using an autoregressive method and slowness and azimuth are estimated using broadband f{-}k analysis in fixed frequency bands and time-windows fixed relative to the initial P-onset time. We demonstrate the improvement to slowness estimates resulting from the use of fixed frequency bands. Events can be located using a single array if, in addition to the P-phase, at least one secondary phase is found with both an acceptable slowness estimate and valid onset-time estimate. We evaluate the on-line system over a twelve month period; every event known to have occured at the mine is detected by the process and 32 out of 53 confirmed events were located automatically. The remaining events were classified as “very likely” Kovdor events and were subsequently located by an analyst. The false alarm rate is low; only 84 very likely Kovdor events were identified during the whole of 2003 and none of these were subsequently located at a large distance from the mine. The location accuracy achieved automatically by the single-array process is remarkably good, and is comparable to that obtained interactively by an experienced analyst using two-array observations. The greatest problem encountered in the single array location procedure is the difficulty in determining arrival times for secondary phases, given the weak Sn phase and the complexity of the P-coda. The method described here could be applied to a wide range of locations and sources for which the monitoring of seismic activity is desirable. The effectiveness will depend upon the distance between source and receiver, the nature of the seismic sources and the level of regional seismicity.     

BOOK REVIEWS

Book Reviewed in this article: Portable Utopia: Glasgow and the United States 1820–1920. Bernard Aspinwall. Studies in Russian Historical Geography. James H. Bater and R. A. French, eds. Water and Sanitation: Economic and Sociological Perspectives. Peter G. Bourne, ed. Green Politics. Fritjof Capra and Charlene Spretnak. The Southern Cone: Realities of the Authoritarian State. César N. Caviedes. Women in Third World Development. Sue Ellen Charlton. Land Management: New Directions. David Chiddick and Alan Millington, eds. Geography and Ethnic Pluralism. Colin Clarke, David Ley, Ceri Peach, eds. Geomorphological Hazards in Los Angeles. R. U. Cooke. Regional Impacts of United States-Mexico Economic Relations. Alfonso Corona and Lay James Gibson. eds. Patterns of Jobs and Geographic Mobility. Torvald Gerger. Cities and Sickness: Health Care in Urban America. Ann Lennarson Greer and Scott Greer, eds. Neighborhoods: Their Place in Urban Life. Howard W. Hallman. Development and the Rural-Urban Divide. John Harriss and Mick Moore, eds. Patterns of Undocumented Migration: Mexico and the United States. Richard C. Jones, ed. Central Place Theory. Leslie J. King. The Geography of Western Europe: A Socio-economic Survey. Paul L. Knox. Regions and Resources: Strategies for Development. David T. Krisge, Daniel A. Seiver, Oliver S. Goldsmith and Michael J. Scott. Geography of Crowding and Human Response. A Study of Ahmedabad City. K. M. Kulkarni. Haciendo Pueblo. The Development of a Guadalajaran Suburb. Kathleen Logan. The Imperial Lion: Human Dimensions of Wildlife Management in Central Africa. Stewart A. Marks. Water in the Hispanic Southwest: A Social and Legal History, 1550–1850. Michael C. Meyer. Imlil: A Moroccan Mountain Community in Change. James A. Miller. Tourism in Canada: Selected Issues and Options. Peter E. Murphy, ed. David Harvey's Geography. John L. Paterson. Raster Scanning, Processing and Plotting of Cartographic Documents. Donna J. Peuquet and A. Raymond Boyle. The USSR and the Muslim World: Issues in Domestic and Foreign Policy. Yaacov Ro'i, ed. Environmental Perception and Behavior: An Inventory and Prospect. Thomas F. Saarinen, David Seamon, and James L. Sell. Incised channels, Morphology, Dynamics, and Control. Stanley A. Schumm, Michael D. Harvey, and Chester C. Watson. The Gap Between Rich and Poor: Contending Perspectives on the Political Economy of Development. Mitchell A. Seligson, ed. Twentieth-Century Richmond. Planning, Politics and Race. Christopher Silver. Land Conservation and Development: Examples of Land-Use Planning Projects and Programs. F. R. Steiner and H. N. van Lier, eds. Biogeography: Recent Advances and Future Directions. J. A. Taylor, ed. Late Quaternary Environments of the Soviet Union. A. A. Velichko, ed. H. E. Wright, Jr. and C. W. Barnosky, eds.     

Accuracy of the spatial representation of the seafloor with bathymetric sidescan sonars

When isobath maps of the seafloor are constructed with a bathymetric sidescan sonar system the position of each sounding is derived from estimates of range and elevation. The location of each pixel forming the acoustic backscatter image is calculated from the same estimates. The accuracy of the resulting maps depends on the acoustic array geometry, on the performances of the acoustic signal processing, and on knowledge of other parameters including: the platform's navigation, the sonar transducer's attitude, and the sound rays' trajectory between the sonar and the seafloor. The relative importance of these factors in the estimation of target location is assesed. The effects of the platform motions (e.g. roll, pitch, yaw, sway, surge and heave) and of the uncertainties in the elevation angle measurements are analyzed in detail. The variances associated with the representation (orientation and depth) of a plane, rectangular patch of the seafloor are evaluated, depending on the geometry of the patch. The inverse problem is addressed. Its solution gives the lateral dimensions of the spatial filter that must be applied to the bathymetric data to obtain specified accuracies of the slopes and depths. The uncertainty in the estimate of elevation angle, mostly due to the acoustic noise, is found to bring the main error contribution in across-track slope estimates. It can also be critical for along-track slope estimates, overshadowing error contributions due to the platform's attitude. Numerical examples are presented.On leave at the Naval Research Laboratory, Code 7420, Washington D.C. 20375-5350, U.S.A.     

植物同工酶基因定位方法初探

根据基因在异源多倍体染色体组间的变异，提出通过缺对一四体和双端体的酶谱分析，无需在不同品种间杂交，即可将同工酶结构基因定位在特定的染色体臂上。还提出，由于等位基因在双体和三体间的变异．通过三体酶谱分析，也能有效地进行同工酶基因定位。     

光学卫星摄影无控定位精度分析

"全球连续覆盖"和"局部区域覆盖"是卫星摄影测量常用的两种摄影模式,两种模式应用目标和无控定位实现途径也各有特点。本文简要介绍了两种模式典型的卫星无控定位精度情况,阐述了光束法平差的关键技术,重点对前方交会和光束法平差无控定位精度进行试验分析。试验结果表明,姿态误差是影响无控定位精度的重要因素,影像分辨率对其影响较小。当外方位角元素误差大于0.5″时,即使影像分辨率为5m,光束法平差后,其无控定位精度也优于0.5m分辨率影像前方交会精度。