POINTE AUTOMATIQUE*     

P. BOIS  M. LA PORTE 《Geophysical Prospecting》1970,18(4):489-504

The automatic picking of seismic sections replaces the slow and painstaking task of manual reflection plotting with rapid and economical processing by computer. Essentially, reflection picking is a decision-making problem which also can be considered as a sort of filtering. Mathematically this means multiplying the seismic data matrix by a more or less complex decision operator. For the sake of economy, we give an initial solution for simple cases which only require easily automatized decision-making criteria. We describe another more elaborate method for use in examining seismic phenomena which are more difficult to spot. The process used is based on the recognition of shapes and consists first of all of determining a series of characteristics capable of identifying each reflection on each trace and then of comparing these different characteristics from trace to trace so as to be able to judge the continuity or discontinuity of the reflections. Automatic picking thus leads to a schematic time-section in which only the horizons found by calculation are retained. An automatic migration program then transforms this time-section into a depth-section.  相似文献   

Deposits and physical properties of pyroclastic density currents during complex Subplinian eruptions: the AD 472 (Pollena) eruption of Somma-Vesuvius, Italy   总被引：2，自引：0，他引：2  

ROBERTO SULPIZIO  DANIELA MELE  PIERFRANCESCO DELLINO  LUIGI LA VOLPE 《Sedimentology》2007,54(3):607-635

Small-scale pyroclastic density currents (PDCs) associated with the AD 472 (Pollena) eruption of Somma-Vesuvius, Italy, were generated by both magmatic and phreatomagmatic explosive fragmentation. The resulting deposits were emplaced under flow boundary conditions dominated by varying combinations of grain interaction, fluid escape and traction processes. Stratigraphic and lithofacies analysis of these PDCs offers a new perspective on the en masse versus progressive aggradation debate for PDC deposition. In particular, the analyses indicate that PDCs were density stratified with a basal underflow dominated by grain interactions. The underflows comprised trains of self-organized granular pulses of variable thickness and magnitude, depending on the overall particle concentration and fluid turbulence. A change in gradient between the upper and lower slopes of the volcano promoted deposition and the different pulses aggraded sequentially (stepwise). In this model each pulse stops en masse and the whole deposit aggrades progressively. Particle concentration, density, mean velocity, and flow height were assessed for the studied PDCs using differaent methods for massive and stratified deposits. The calculated mobility of the flows was 0·2 to 0·3, in the expected range for small-scale PDCs.  相似文献   

Application of Natural Attenuation to Ground Water Contaminated by Phenoxy Acid Herbicides at an Old Landfill in Sjoelund, Denmark   总被引：1，自引：0，他引：1  

Nina Tuxen  Palle Ejlskov  Hans-Jørgen Albrechtsen  Lotte A. Reitzel  Jørn K. Pedersen  Paul L. Bjerg 《Ground Water Monitoring & Remediation》2003,23(4):48-58

Investigations of geology, hydrogeology, and ground water chemistry in the aquifer downgradient from Sjoelund Landfill, Denmark, formed the basis for an evaluation of natural attenuation as a remediation technology for phenoxy acid herbicides at the site. Concentrations of phenoxy acids were up to 65 μg/L in the ground water, primarily 4-chlor-2-methylphenoxypropionic acid (MCPP) and 2,4-dichlorophenoxypropionic acid (dichlorprop). Mass removal of the phenoxy acids was shown within 50 to 100 m of the landfill by calculation of contaminant fluxes passing transects at three distances. There was accordance between increasing oxygen concentrations and decreasing phenoxy acid concentrations with distance from the landfill, indicating that aerobic degradation was a major mass removal process. Presence of high concentrations of putative anaerobic phenoxy acid metabolites suggested that anaerobic degradation was also occurring. Laboratory degradation experiments using sediment and ground water from the aquifer supported aerobic and anaerobic degradability of MCPP at the site. It was concluded that natural attenuation may be applicable as a remedy for the phenoxy acids at the Sjoelund Landfill site, although uncertainties related to calculations of chloride and phenoxy acid fluxes at a complex site and identification of specific in situ indicators were encountered. Thus, there is a pronounced need for development and broader experience with evaluation tools for natural attenuation of phenoxy acids, such as specific metabolites, changes in enantiomeric fractions, compound-specific stable carbon isotope ratios, or microbial fingerprints.  相似文献   

Rapport (1966–1976) sun les Eléments en Traces Dans Trois Roches Standards Géochimiques Du CRPG . Basalte BR et Granites, GA et GH     

K. GOVINOARAJU  H. DE LA  ROCHE 《Geostandards and Geoanalytical Research》1977,1(1):67-100

Cinquième de la serie des rapports d'étude coopérative sur les standards géochimiques du CRPG, ce rapport est consacré exclusivement aux éeléments en traces dans trois éahantillons en circulation depuis 1963: les Granites GA et GH et le Basalte BR. La pré-sentation de plus de 2000 données analytiques réporties sur 50 éléments est accompagnée d'une évaluation statistique et critique, échantillon par éahmtillon et élément par élément. La discussion est menée dans le sens d'un dialogue direct avec I'utilisateur en nuançant et en hiérarchieant les valeurs que nous veoamnandons ou proposons. Quant à I'analyste practician, il trouvera une table des valeurs "utilisables" pour une trentaine d'éléments dans les trois échantillons de référence (Table 4). Rappelons que ces échantillons sont déjà bien caractérises en ce qui concerne leurs constituants majeurs et mineurs, grâce aux quatre rapports d'étude coopérative dont le dernier est paru en 1370.  相似文献   

石墨炉原子吸收光谱法测定味精中痕量铅的不确定度评定   总被引：4，自引：0，他引：4  

王玉功  李国兵  拉毛吉  王建波 《岩矿测试》2009,28(2):165-168

以石墨炉原子吸收光谱法测定味精中痕量铅为例,对测定结果的不确定度来源进行分析,对测定过程的主要不确定度分量进行合理评定,包括称量不确定度、体积不确定度、曲线拟合不确定度及测量重复性引入的不确定度。评估了铅含量的合成标准不确定度和扩展不确定度。对于铅含量为0.025×10-6的味精样品,其扩展不确定度为0.002×10-6。  相似文献   

青藏铁路建设冻土工程问题的深入研究和实践   总被引：6，自引：1，他引：5  

拉有玉  张鲁新 《冰川冻土》2005,27(1):46-49

青藏铁路开工建设以来的冻土工程问题研究, 在综合以往冻土学研究成果基础上, 针对冻土区大规模工程实践对冻土和冻土环境的影响特点, 冻土和冻土工程之间相互作用本质, 用系统工程论的观点, 以工程变形为冻土工程问题研究的综合目标, 抓住冻土工程问题的热学机理本质, 用工程热力结构作为解决问题的主要手段, 取得很好的实践效果. 同时把我国冻土工程问题研究和冻土工程建设提高到一个新的水平, 为建设世界一流的高原铁路奠定了坚实的技术基础.  相似文献   

1960-2012年河西内陆河上游山区降水量变化及其区域性差异分析     

蓝永超  刘金鹏  丁宏伟  鲁承阳  沈永平  胡兴林  喇承芳  宋洁  高黎明 《冰川冻土》2013,35(6):1474-1480

基于我国河西内陆河流域有关水文、气象台站的观测数据,对1960年代以来河西走廊的石羊河、黑河、疏勒河三大内陆河水系上游山区降水变化特征、趋势及区域时空变化差异进行了分析.结果表明：受全球变暖的影响,石羊河、黑河、疏勒河流域上游的降水量年代际、年际及季节性的变化总体上呈增加的态势,但不同区域降水增幅存在着一定的差异.其中,1960年代,位于祁连山东部的石羊河水系上游山区、中部的黑河水系上游山区及西部的疏勒河水系上游山区普遍少雨;1970年代,石羊河山区降水偏多并持续至今,黑河、疏勒河水系上游山区则降水偏少;1980年代,三大水系上游山区均多雨;1990年代的黑河、疏勒河山区和2000年代的三大水系上游山区均多雨;2010年以来,黑河山区降水偏少,石羊河与疏勒河山区降水均偏多.相对而言,位于祁连山西部山区的疏勒河水系上游年降水量与夏季降水量的增长较为显著.  相似文献   

Oxygen-enhanced biodegradation of phenoxy acids in ground water at contaminated sites   总被引：1，自引：0，他引：1  

Tuxen N  Reitzel LA  Albrechtsen HJ  Bjerg PL 《Ground water》2006,44(2):256-265

The effects of adding oxygen to anaerobic aquifer materials on biodegradation of phenoxy acid herbicides were studied by laboratory experiments with aquifer material from two contaminated sites (a former agricultural machinery service and an old landfill). At both sites, the primary pollutants were phenoxy acids and related chlorophenols. It was found that addition of oxygen enhanced degradation of the six original phenoxy acids and six original chlorophenols. Inverse modeling on 14C 4-chloro-2-methylphenoxypropanoic acid (MCPP) degradation curves revealed that increasing the oxygen concentrations from <0.3 mg/L up to 7 to 8 mg/L shortened the lag phases (from approximately 150 d to 5 to 25 d) and increased first-order degradation rate constants by 1 order of magnitude (from approximately 5 x 10(-2) d(-1) to up to 30 x 10(-2) d(-1)). Additionally, the degree of MCPP mineralization was increased (30% to 50% mineralized at low oxygen concentrations and 50% to 70% mineralized at high oxygen concentrations, based on 14CO2 recovery). These positive effects on degradation were observed even at relatively low oxygen concentrations (2 mg/L). Furthermore, effects related to the addition of oxygen on the general geochemistry were studied. An oxygen consumption of 2.2 to 2.6 mg O2/g dw was observed due to oxidation of solid organic matter and, to some extent (0.5% to 11% of the total oxygen consumption), water-soluble compounds such as Fe2+, dissolved Mn, nonvolatile organic carbon, and NH4+. Overall, the results suggest that stimulated biodegradation by addition of oxygen might be a feasible remediation technology at herbicide-contaminated sites, although oxygen consumption by the sediment could limit the applicability.  相似文献