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961.
苏北王港近岸表层沉积物元素地球化学特征与环境意义 总被引:1,自引:0,他引:1
对王港河河道及河口附近潮滩典型地貌部位表层沉积物粒度、常量和微量元素进行分析,结果表明:潮滩和河道近岸沉积物为粘土质粉砂,粒度分布频率曲线在平均高潮线附近的沉积物为双峰态外,其余为单峰态。互花米草滩沉积物中常量和微量元素(Al2O3,TiO2,CaO,Fe2O3,K2O,MgO,MnO和Cu,Rb,Pb,As,Zn)均表现出相对富积的特征,盐蒿滩次之,反映海岸带互花米草在削浪促淤的过程中,对重金属污染有效吸附作用比盐蒿潮滩滩大。SiO2化学性质比较稳定,对沉积地貌动力的响应比较显著,近岸高潮线附近和河道中主洪道沉积物SiO2含量明显偏高。河闸上游河道沉积物中烧失量、磷(P2O5)、硫(稳定态SO3)的含量最高,反映流域营养盐在水闸以上河段沉积物中富积,重金属元素Rb,Pb,As,Ba在河道沉积物中与地壳风度相比表现为富集。王港附近潮滩表层沉积物物质组成不仅与王港河、黄河及长江的物质来源有关,而且与古潮滩沉积再搬运、再沉积以及人类围垦及排放污染活动有关。As,S是该区主要的污染元素。 相似文献
962.
963.
本文从对震害进行分析和研究的目的出发,讨论了航空遥感飞行与影像图制作的有关技术和实施问题,主要包括在震害研究和调查中,航摄与制图比例尺的选择、航空遥感飞行的方案设计、利用影像图进行震害研究分析的优越性及系列震害专题影像图的确定与制作特点等内容。 相似文献
964.
Geochemistry of Flood Basalts of the Toranmal Section, Northern Deccan Traps, India: Implications for Regional Deccan Stratigraphy 总被引:12,自引:0,他引:12
MAHONEY J. J.; SHETH H. C.; CHANDRASEKHARAM D.; PENG Z. X. 《Journal of Petrology》2000,41(7):1099-1120
Tholeiitic lavas forming a flood basalt sequence of 870 m thicknessat Toranmal in the northern Deccan Traps have a large rangein isotopic ratios [ 相似文献
965.
UDEC modeling of a field explosion test 总被引:7,自引:0,他引:7
S. G. Chen J. Zhao Y. X. Zhou 《Fragblast: International Journal for Blasting and Fragmentation》2000,4(2):149-163
A field explosion test is conducted to investigate the blast wave characteristics and propagation in jointed rock mass. A hybrid AUTODYN and UDEC scheme is used to predict the rock mass response due to the explosion. The original prediction is then modified by involving the actual test conditions and dynamic equation of state of the rock material. Correlating the prediction results with the field explosion test results shows that the hybrid AUTODYN and UDEC scheme is capable of modeling explosion problems with high reliability. It is observed that the modified prediction result agrees better with the field test result than the original prediction result, which implies that involving dynamic parameters in the modeling is very important to produce reliable prediction results. 相似文献
966.
967.
Flow liquefaction and cyclic mobility are two different phenomena that are encountered during strong earthquakes. Flow liquefaction is associated with the contractive behavior of loose granular materials and cyclic mobility is associated with the dilative response of both loose and dense granular materials at low confining stresses. These two types of response pertain to the same material and therefore should be modeled in a consistent manner. Whether a soil in a given state exhibits contractive or dilative behavior is dependent on its dilatancy, d=dvp/dqp. A form of the dilatancy d=d(η,ψ,C) is proposed, where η=q/p is the stress ratio, and ψ and C denote the internal state variables and the intrinsic properties, respectively. It has been shown that such a state-dependent dilatancy is effective in describing both the contractive and dilative behavior. This allows the soil behavior associated with flow liquefaction and cyclic mobility during earthquakes to be modeled in a unified way. 相似文献
968.
预应力混凝土结构非线性地震反应分析 总被引:4,自引:0,他引:4
本文针对预应力混凝土与普通混凝土不同的受力特点,提出了适合于分析预应力混凝土结构抗震性能的非线性有限元模型。模型首先将混凝土结构离散为杆单元,然后对各杆单元按分层组合原理分成许多混凝土层、预应力钢筋层和普通钢筋层,计算混凝土分层单元、预应力钢筋和普通钢筋的应力和应变,最后,根据钢筋与混凝土之间的粘结-滑移关系高速钢筋变形,根据混凝土弹性模量调整结构及杆单元变形,通过对普通混凝土构件和三个预应力混凝 相似文献
969.
金家庄超基性岩型金矿围岩蚀变地球化学研究 总被引:3,自引:0,他引:3
金家庄金矿近围岩蚀变为蛇纹石化、滑石化、碳酸盐化和硅化。岩石化学与微量元素研究表明,从未蚀变-强蚀变透辉岩至矿化蚀变岩,SiO2、CaO、Al2O3含量逐渐降低,CO2、H2O、S和Au、Ag、Cu含量逐渐增高。蚀变岩石同位素研究揭示,碳同位素较低(δ^18O=12.10‰~22.3‰)远高于超基性岩正常范围。围岩蚀变热液主要源于大气降水、碳、硫和成矿元素主要是在围岩蚀变过程中从超基性岩中萃取。 相似文献
970.
C. Covey A. Abe-Ouchi G. J. Boer B. A. Boville U. Cubasch L. Fairhead G. M. Flato H. Gordon E. Guilyardi X. Jiang T. C. Johns H. Le Treut G. Madec G. A. Meehl R. Miller A. Noda S. B. Power E. Roeckner G. Russell E. K. Schneider R. J. Stouffer L. Terray J.-S. von Storch 《Climate Dynamics》2000,16(10-11):775-787
We examine the seasonal cycle of near-surface air temperature simulated by 17 coupled ocean-atmosphere general circulation models participating in the Coupled Model Intercomparison Project (CMIP). Nine of the models use ad hoc “flux adjustment” at the ocean surface to bring model simulations close to observations of the present-day climate. We group flux-adjusted and non-flux-adjusted models separately and examine the behavior of each class. When averaged over all of the flux-adjusted model simulations, near-surface air temperature falls within 2?K of observed values over the oceans. The corresponding average over non-flux-adjusted models shows errors up to ~6?K in extensive ocean areas. Flux adjustments are not directly applied over land, and near-surface land temperature errors are substantial in the average over flux-adjusted models, which systematically underestimates (by ~5?K) temperature in areas of elevated terrain. The corresponding average over non-flux-adjusted models forms a similar error pattern (with somewhat increased amplitude) over land. We use the temperature difference between July and January to measure seasonal cycle amplitude. Zonal means of this quantity from the individual flux-adjusted models form a fairly tight cluster (all within ~30% of the mean) centered on the observed values. The non-flux-adjusted models perform nearly as well at most latitudes. In Southern Ocean mid-latitudes, however, the non-flux-adjusted models overestimate the magnitude of January-minus-July temperature differences by ~5?K due to an overestimate of summer (January) near-surface temperature. This error is common to five of the eight non-flux-adjusted models. Also, over Northern Hemisphere mid-latitude land areas, zonal mean differences between July and January temperatures simulated by the non-flux-adjusted models show a greater spread (positive and negative) about observed values than results from the flux-adjusted models. Elsewhere, differences between the two classes of models are less obvious. At no latitude is the zonal mean difference between averages over the two classes of models greater than the standard deviation over models. The ability of coupled GCMs to simulate a reasonable seasonal cycle is a necessary condition for confidence in their prediction of long-term climatic changes (such as global warming), but it is not a sufficient condition unless the seasonal cycle and long-term changes involve similar climatic processes. To test this possible connection, we compare seasonal cycle amplitude with equilibrium warming under doubled atmospheric carbon dioxide for the models in our data base. A small but positive correlation exists between these two quantities. This result is predicted by a simple conceptual model of the climate system, and it is consistent with other modeling experience, which indicates that the seasonal cycle depends only weakly on climate sensitivity. 相似文献