Seasonal dynamics of elemental sulfur in two coastal sediments   总被引：1，自引：0，他引：1  

Henning Troelsen  Bo Barker Jørgensen 《Estuarine, Coastal and Shelf Science》1982,15(3):255-266

A spectrophotometric method for elemental sulfur (S⁰) analysis without interference from other reduced sulfur compounds was adapted for the use in reducing sediments. The S⁰ distribution in two coastal sediments was studied regularly from summer to winter and compared to factors regulating the S⁰ accumulation, such as redox potentials, the rate of bacterial sulfide production and the general sulfur chemistry. Dense coatings of sulfur bacteria developed on the sediment surface of a sulfuretum which had an S⁰ concentration of up to 41 μmol S cm^?3. The 2·5-mm thick bacterial coating contained 40% of all S⁰ in the sediment. A more typical marine sediment with a few cm thick oxidized surface layer had an S⁰ maximum of 1–3 μmol S cm^?3 at 2–4 cm depth. The S⁰ maximum in both sediments increased from summer to winter as the sediments gradually became more oxidized. The deeper layers maintained a low S⁰ concentration. Most of the S⁰ in the upper few mm of a laboratory sulfuretum was present inside sulfur bacteria and actively migrated up and down with the bacteria depending upon the changing light and oxygen conditions.  相似文献   

油气化探同步荧光技术中的若干问题     

胡斌  李广之  程桂  袁子艳 《物探与化探》2008,32(5):470-472

在试验的基础上,对油气化探固定波长同步荧光测试技术中光谱图的认识、波长差与方法灵敏度的关系以及同步荧光与其他荧光方法的内在关系等问题作了深入的研究和探讨,澄清了该技术在实际应用工作中较易产生混淆的几个问题,旨在推动该项技术在油气化探工作中的进一步应用和发展.  相似文献   

Geochemical Mapping: With Special Emphasis on Analytical Requirements     

XIE Xuejing  CHENG Hangxin  LIU Dawen 《《地质学报》英文版》2008,82(2):451-462

More than 40 national and regional geochemical mapping projects in the world carried out from 1973 to 1988 do not conform to common standards. In particular they have many analytical deficiencies. In the period 1988 to 1992, the International Geochemical Mapping project （Project 259 of UNESCO＇s IGCP Program） prepared recommendations designed to standardize geochemical mapping methods. The analytical requirements are an essential component of the overall recommendations. They included the following： 71 elements should be analyzed in future mapping projects; the detection limits of trace and ultratrace elements must be lower than the corresponding crustal abundances; and the Chinese GSD and Canadian STSD standard sample series should be used for the correlation of global data. A proposal was also made to collect 5000 composite samples, at very low sampling densities to cover the whole Earth＇s land surface. In 1997 an IUGS Working Group on Global Geochemical Baselines was formed to continue the work which began with IGCP 259. From 1997 up to now, new progress has been made especially in China and FOREGS countries under the aegis of this working group, including the study of suitable sampling media, development of a multi-element analytical system, new proficiency test for selection of competent laboratories and role of wide-spaced mapping in mineral exploration. One of the major problems awaiting solution has been the inability of many laboratories to meet the IGCP recommendations to generate high quality geochemical maps. Fortunately several laboratories in China and Europe have demonstrated an ability to meet the requirements and they will be well placed to render technical assistance to other countries.  相似文献   

建筑物沉降监测专家分析系统设计与开发     

董春来  吴雪燕  蒋廷臣 《测绘与空间地理信息》2008,31(6)

建筑物沉降监测数据分析与处理是一项较复杂的系统工程,本文从自动化处理观点出发,介绍了设计沉降监测专家分析系统的咨询新理念和主体思想,探讨了开发选用的数学模型与开发过程,以期为相关变形监测与分析提供帮助和启示.  相似文献   

A virtual voyage through 3D structures generated by chaotic mixing of magmas and numerical simulations: a new approach for understanding spatial and temporal complexity of magma dynamics     

Diego Perugini  Maurizio Petrelli  Giampiero Poli 《Visual Geosciences》2008,13(1):1-24

In this contribution, we present a virtual voyage through 3D structures generated by chaotic mixing of magmas and numerical simulations with the aim to highlight the power of 3D representations in the understanding of this geological phenomenon. In particular, samples of mixed juveniles from Salina island (Southern Italy) are reconstructed in 3D by serial lapping and digital montage and numerical simulations are performed by using a 3D chaotic dynamical system. Natural and simulated magma mixing structures are visualized by using several multimedia tools including animations and “virtual reality” models. It is shown that magma interaction processes can generate large spatial and temporal compositional heterogeneities in magmatic systems. The same topological structures are observed in both 3D reconstructed rock samples and chaotic numerical simulations, indicating that the mixing of magmas is governed by chaotic dynamics. The use of 3D multimedia models gives the opportunity to penetrate into magma mixing structures and to understand their significance in the context of magma dynamics. Such an approach is very powerful since multimedia tools can strongly capture the attention of the reader bringing him/her into an interactive and memorable geological experience. Electronic supplementary material  enclosed:  相似文献   

Probabilistic modeling of seismically triggered landslides using Monte Carlo simulations     

Huabin Wang  Gonghui Wang  Fawu Wang  Kyoji Sassa  Yuping Chen 《Landslides》2008,5(4):387-395

The 2004 Chuetsu earthquakes of Niigata (Japan) triggered numerous landslides, and the most widespread types of landslides were highly disrupted, relatively shallow slides and soil (debris) flows. This paper presented a method to evaluate slope instability using Newmark displacement on a pixel-by-pixel basis in a given area. The proposed method was able to integrate Newmark displacement modeling and Monte Carlo simulations within geographical information systems. In the modeling, an empirical attenuation relationship was utilized to calculate Arias intensity over this study area, and the variability of geotechnical parameters was taken into account to calculate coseismic landslide displacement. Before deriving the displacement from related inputs, the Monte Carlo simulations ran 1,500 times and generated 1,500 displacement values for each grid cell, and then means and standard deviations of displacement were calculated and probabilistic distributions can be obtained. Finally, given 10 cm as a threshold value of displacement, estimated probabilities of displacement exceeding 10 cm were shown as a map of seismic landslide hazards. The resulting hazard map was classified into four categories from very low to high level.  相似文献   

An overview of focuses of research on otolith element characteristics and general testing methods     

GAO Yong-Hua LI Qing-Rong LIN Dong-Ni JIAO Chi FENG Qiang-Ling 《地学前缘》2008,15(6):11

  相似文献   

我国煤炭航测技术的最新发展     

赖百炼 《中国煤炭地质》2008,(11):81-83

中国煤炭地质总局航测遥感局作为我国煤炭航测技术的主要单位,承担着95％以上的煤炭矿区航测成图任务,并逐步发展成为我国集航空摄影、遥感地质、地图制印、地下管线探测、地理信息技术等全面发展的空间信息产业集团：伴随着计算机技术的发展,煤炭航测技术走过了从模拟测图到解析测图,最后发展到今天的全数字测图的历程。目前煤航已拥有和掌握了IMU／DGPS辅助航空摄影技术、SAR（合成孔径雷达）成图技术、LIDAR（机载激光扫描）技术等空间数据采集最新技术。  相似文献   

Efficient generation of conditional simulations by chebyshev matrix polynomial approximations to the symmetric square root of the covariance matrix     

C. R. Dietrich  G. N. Newsam 《Mathematical Geology》1995,27(2):207-228

Consider the problem of generating a realization y₁ of a Gaussian random field on a dense grid of points ₁ conditioned on field observations y₂ collected on a sparse grid of points ₂. An approach to this is to generate first an unconditional realization y over the grid =_{1 2}, and then to produce y₁ by conditioning y on the data y₂. As standard methods for generating y, such as the turning bands, spectral or Cholesky approaches can have various limitations, it has been proposed by M. W. Davis to generate realizations from a matrix polynomial approximations to the square root of the covariance matrix. In this paper we describe how to generate a direct approximation to the conditional realization y₁, on ₁ using a variant of Davis' approach based on approximation by Chebyshev polynomials. The resulting algorithm is simple to implement, numerically stable, and bounds on the approximation error are readily available. Furthermore we show that the conditional realization y₁ can be generated directly with a lower order polynomial than the unconditional realization y, and that further reductions can be achieved by exploiting a nugget effect if one is present. A pseudocode version of the algorithm is provided that can be implemented using the fast Fourier transform if the field is stationary and the grid ₁ is rectangular. Finally, numerical illustrations are given of the algorithm's performance in generating various 2-D realizations of conditional processes on large sampling grids.  相似文献   

Large eddy simulation of hydrocyclone—prediction of air-core diameter and shape     

M. Narasimha  Mathew Brennan  P.N. Holtham 《International Journal of Mineral Processing》2006

Hydrocyclones are widely used in the mining and chemical industries. An attempt has been made in this study, to develop a CFD (computational fluid dynamics) model, which is capable of predicting the flow patterns inside the hydrocyclone, including accurate prediction of flow split as well as the size of the air-core. The flow velocities and air-core diameters are predicted by DRSM (differential Reynolds stress model) and LES (large eddy simulations) models were compared to experimental results. The predicted water splits and air-core diameter with LES and RSM turbulence models along with VOF (volume of fluid) model for the air phase, through the outlets for various inlet pressures were also analyzed. The LES turbulence model led to an improved turbulence field prediction and thereby to more accurate prediction of pressure and velocity fields. This improvement was distinctive for the axial profile of pressure, indicating that air-core development is principally a transport effect rather than a pressure effect.  相似文献