MISCELLANEA     

Everett K. Gibson 《Meteoritics & planetary science》1975,10(3):287-288

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DISCOVERY OF ANOTHER METEORITE SPECIMEN FROM THE 1912 HOLBROOK,ARIZONA FALL SITE     

Everett K. Gibson 《Meteoritics & planetary science》1970,5(1):57-60

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DNAPL Characterization Methods and Approaches, Part 1: Performance Comparisons   总被引：4，自引：0，他引：4  

Mark L. Kram  Arturo A. Keller  Joseph Rossabi  Lorne G. Everett 《Ground Water Monitoring & Remediation》2001,21(4):109-123

Contamination from the use of chlorinated solvents, often classified as dense nonaqueous phase liquids (DNAPLs) when in an undissolved state, represents an environmental challenge with global implications. Mass-transfer limitations due to rate-limited dissolution can lead to long-term aquifer persistence for even small volumetric fractions. The identification of DNAPL source zones located beneath the water table is critical to ultimately achieve site remediation and aquifer restoration. This paper provides a comparison of the advantages and disadvantages of many of the methods being used for detecting and delineating DNAPL contaminant source zones. The objective is to determine which options are best to pursue based on site characteristics, method performance, and method costs. DNAPL characterization methods are grouped into approaches, which include site preparation, characterization, and data-processing activities necessary to design an effective remediation system. We compare the different approaches based on the level of chemical and hydrogeologic resolution, and the need for additional data requirements. Our findings can be used to assist with selection of appropriate site remediation management options.  相似文献   

A three-dimensional spherical mesh generator     

M. E. Everett 《Geophysical Journal International》1997,130(1):193-200

A new spherical mesh generator is described. It represents an efficient, deterministic packing of tetrahedra into a solid sphere, a spherical shell, or both. The mesh can be used for finite-element solutions to a wide variety of global numerical modelling problems in the geosciences. The nodes within the mesh are distributed uniformly, and long, thin tetrahedra are avoided. The method proposed here offers several advantages over 3-D Delaunay algorithms for finite-element mesh generation. For the related problem of trivariate scattered data interpolation, which is not considered here, the 3-D Delaunay algorithms are the method of choice.  相似文献   

Calculated geochronology and stress field orientations along the Hawaiian chain     

Everett D. Jackson  Herbert R. Shaw  Keith E. Bargar 《Earth and Planetary Science Letters》1975,26(2):145-155

A new method has been discovered for calculating ages of the main shield building stages of volcanoes along the Hawaiian chain from Kilauea to the Hawaiian-Emperor bend. The method is based on a graphical technique for hypothetical subtraction of distance intervals that theoretically represent regions of simultaneous volcanism along adjacent or nearly en-echelon loci of volcanism. Distances along the chain, measured from Kilauea, when progressively foreshortened by the distances of hypothetical “collapse” and plotted versus existing age data are found to give linear age-distance relationships. A calibration graph is presented that agrees closely with the measured ages in 17 of the 20 existing dated volcanoes. The criterion for simultaneous activity on different loci is based on the concept of equal azimuths of synchronous volcanic propagation within coeval segments of the chain. This is the predicted relationship when magmatic fluids inject the lithosphere along directions normal to a nearly horizontal least principal stress. It appears that the Pacific plate has been subjected to oscillatory, but principally clockwise, rotations of horizontal stress components during the last 40 m.y.  相似文献   

Prediction of well levels in the alluvial aquifer along the lower Missouri River     

Criss RE  Criss EM 《Ground water》2012,50(4):571-577

Temporal variations in the head of wells in the alluvial aquifer along the lower Missouri River are accurately simulated by summation of linear differential terms involving daily variations in river stage and effective precipitation. Scaling parameters were optimized using a fourth order Adams-Bashforth-Moulton method, providing predictions for head that are typically accurate within ±1.5 feet (0.5 m) over intervals of 1 to 15 years. Parameter magnitudes represent the product of realistic aquifer properties and geometric factors.  相似文献   

Unexploded ordnance discrimination using time-domain electromagnetic induction and self-organizing maps     

Alfonso Benavides I  Mark E. Everett  Carl Pierce Jr. 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(2):169-179

Self-organizing maps (SOM) are implemented for discrimination of geologic noise, buried metal objects and unexploded ordnance using the geophysical method of time-domain electromagnetic induction. The learning and misfit measures are based on a Euclidean metric. The U*-matrix method is shown to be a reliable tool for determining data clusters and cluster boundaries. The performance of SOM for data-type discrimination was tested using three synthetic, idealized geophysical datasets consisting of exponential, multi-exponential and stretched-exponential decaying transients. In addition, experimental data were acquired using a modified Geonics EM63 instrument. Results from the synthetic examples show that SOM clusters the data based on their functional origin, when represented using U*-matrices. The percentage of correct classification is 100%. Unsupervised learning using the field dataset obtained with the Geonics EM63 succeeded in producing a multi-clustered map in which the background transients cluster themselves and are separated from clusters associated with metal clutter objects and UXO. Even though in some cases the SOM did not produce a single cluster for each type of causative body, it was able to separate clutter data from target data by producing several small clusters. The results are encouraging in view of the heterogeneity and sparsity of the training dataset.  相似文献   

海底电性源频率域CSEM勘探建模及水深影响分析   总被引：4，自引：3，他引：1       下载免费PDF全文

刘长胜  Mark E. Everett  林君  周逢道 《地球物理学报》2010,53(8):1940-1952

为了探索我国海域油气和水合物等高阻目标体CSEM勘探的可行性和方法技术,本文研究了在海水中水平电性源激励下有限水深海洋地电模型的频率域电磁响应,为进一步的1D和3D仿真计算奠定了理论基础.在推导电磁响应公式时,首先给出了各层介质的Lorentz势,然后根据Coulomb势与Lorentz势的关系,得到了各层介质的Coulomb势.各层介质中的电磁场均可以由Lorentz势或者Coulomb势计算得到,但在有限元计算时Coulomb势具有优势.长导线源的电磁场和势函数可以由电偶源的电磁场和势函数沿导线长度积分得到.文中具体给出了海水中水平电偶源和长导线源在海水层的电磁场公式,并根据该公式计算了不同水深环境下海底表面的电磁场分布,分析了海水深度对海底油气储层电磁异常的影响.结果表明,随着水深减小,异常幅度和形态特征发生明显变化.当水深很浅时(如50 m),只有同线方向的E_x和E_z两个电场分量存在明显异常.最后,以两个已知海底油田为例,计算了不同水深环境下可观测到的电场异常,展示了电性源频率域CSEM在海底勘探中(包括浅海环境)的良好应用前景.对于该方法实用化过程中还需进一步解决的问题,文中结尾部分也进行了初步探讨.  相似文献   

Find A Falling Star,by Harvey H. Nininger     

Everett K. Gibson 《Meteoritics & planetary science》1973,8(2):186-187

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SULFUR IN ACHONDRITIC METEORITES     

Everett K. Gibson  Carleton B. Moore  Thomas M. Primus  Charles F. Lewis 《Meteoritics & planetary science》1985,20(3):503-511

Total sulfur abundances have been measured for 48 achondrites. For twenty eucrites they ranged from 370 to 3700 μgS/g with a median sulfur content of 1180 μgS/g. Sulfur abundances for howardites ranged from 1490 to 3240 μgS/g and had a median sulfur concentration of 2340 μgS/g. Diogenites' sulfur abundances ranged from 130 to 3170 μgS/g, with a median value of 1280 μgS/g. Four shergottites had a median sulfur content of 1940 μgS/g and ranged from 740 to 2540 μgS/g. Enstatite achondrites contained the greatest sulfur abundances of any achondrite group. They ranged from 2450 to 8580 μgS/g and had a median sulfur content of 6020 μgS/g. A single Chassignite had a sulfur concentration of 360 μgS/g. The wide variations in sulfur concentrations for the achondrites reflect the small scale heterogeneous nature of these unique extraterrestrial materials due in large part to discrete sulfide mineral grains.  相似文献