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151.
水—岩相互作用前锋的形态可以自组织成非平面形,如指形和扇形。这是由于外界流体驱动下的聚流作用而形成的。对于碳酸盐胶结的砂岩,这种现象用一组反应—运移方程来模拟,设计一套计算机程序解此方程组,并用以预测这种现象的时间演化。该程序含有许多特别的数值算法,以使计算迅速收敛。文中阐明了前锋成指形、扇形、指尖分裂形和帽形的效应。文中研究了流速、流渠宽度、以及围岩中胶结物(方解石或白云石)的变化的影响。本文讨论了这种模拟对于加深认识成岩作用和石油工程的潜在重要性。 相似文献
152.
某国外刊物报导说:美国军阀已使国际测量协会为自己服务。为证实这个机构如何变为美军指挥部的顺从工具,就必须阐明它在第二次世界大战后数年内的活动。 相似文献
153.
A protocol for detecting hepatic micronuclei in fish was performed to check genotoxic damage, as an indicator of environmental hydrocarbons exposure, in relation to the "Haven" oil spill. As target fish, we have chosen three demersal species with different habitats and feeding behaviour (i.e., Lepidorhombus boscii, Merluccius merluccius and Mullus barbatus) collected from two differently impacted areas and a control site. Additional analysis was performed by histological detection of hepatic tissue damages such as the presence of necrotic and tumour-like aspects. The three studied species showed different sensitivity to environmental pollutants exposure, L. boscii resulting the more sensitive in terms of both micronuclei incidence and tissue damage. The results of this study show that: (1) the micronucleus test could be an effective and fast method to detect oil pollution; (2) a clear response of L. boscii only to oil contamination for both micronucleus test and liver tissue alterations. 相似文献
154.
Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in sediments from Hong Kong 总被引:4,自引:0,他引:4
Müller JF Gaus C Prange JA Päpke O Poon KF Lam MH Lam PK 《Marine pollution bulletin》2002,45(1-12):372-378
Concentrations of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were determined in 14 sediment samples collected from four sites in the Mai Po Marshes Nature Reserve (within a RAMSAR Site) and from another six sites in Victoria Harbour and along the Hong Kong coastline. Elevated levels of PCDDs, and particularly OCDD, were detectable in all samples collected from the Mai Po Marshes and five of the six sites. In contrast to PCDDs, PCDFs were mainly found in sediment samples collected from industrial areas (Kwun Tong and To Kwa Wan) in Victoria Harbour. PCDD/F levels and congener profiles in the samples from the Mai Po Marshes Nature Reserve in particular show strong similarities to those reported in studies which have attributed similar elevated PCDD concentrations to nonanthropogenic PCDD sources. 相似文献
155.
Davis JA May MD Greenfield BK Fairey R Roberts C Ichikawa G Stoelting MS Becker JS Tjeerdema RS 《Marine pollution bulletin》2002,44(10):1117-1129
In 1997, seven sport fish species were sampled from seven popular fishing areas in San Francisco Bay. Mercury exceeded a human health screening value in 44 of 84 (52%) samples. All collected samples of leopard shark and striped bass exceeded the mercury screening value of 0.23 microg/g wet weight. PCBs exceeded the screening value in 51 of 72 (71%) samples. DDT, chlordane, and dieldrin, had lower numbers of samples above screening values: 16 of 72 (22%) for DDT, 11 of 72 (15%) for chlordanes, and 27 of 72 (37%) for dieldrin. Concentrations of PCBs and other trace organics were highest in white croaker and shiner surfperch, the two species with the highest fat content in their muscle tissue. Fish from one location, Oakland Harbor, had significantly elevated wet weight concentrations of mercury, PCBs, DDTs, and chlordanes compared to other locations. Removal of skin from white croaker fillets reduced lipid concentrations by 27-49% and concentrations of trace organics by 33-40%. 相似文献
156.
Hurley K Strohmayer T Li P Kouveliotou C Woods P van Paradijs J Murakami T Hartmann D Smith I Ando M Yoshida A Sugizaki M 《The Astrophysical journal》2000,528(1):L21-L23
We present a 2-10 keV ASCA observation of the field around the soft gamma repeater SGR 1627-41. A quiescent X-ray source, whose position is consistent both with that of a recently discovered BeppoSAX X-ray source and with the Interplanetary Network localization for this soft gamma repeater, was detected in this observation. In 2-10 keV X-rays, the spectrum of the X-ray source may be fit equally well by a power-law, blackbody, or bremsstrahlung function, with unabsorbed flux approximately 5x10-12 ergs cm-2 s-1. We do not confirm a continuation of a fading trend in the flux, and we find no evidence for periodicity, both of which were noted in the earlier BeppoSAX observations. 相似文献
157.
The crustal-scale Kyonggi shear zone of central Korea has been identified as a major boundary between the Precambrian Kyonggi massif in the south and the Imjingang belt in the north. The latter is an eastward extension of the Qinling-Dabie-Sulu collisional belt of China. Field observations and microstructural analysis indicate that the extensional shear zone evolved from a deep crustal ductile regime to a shallow crustal brittle regime, associated with a rapid uplift of the Kyonggi massif following the Late Permian-Early Triassic collision between the Sino-Korean and Yangtze cratons. A Rb-Sr muscovite age (226+/-1.2 Ma) of the mylonite suggests that the extensional ductile shearing occurred during the Late Triassic. 相似文献
158.
在仅约200年的时间跨度内库奇盆地就发生了2次大地震(M〉7.5),这对于稳定地块内部的地区来说十分罕见(图1)。哪些因素有可能造成该地区与其他地方的板块内环境不同?是其中的一些因素造成相对较短复发周期吗?构造演化历史能提供任何有关该板块内部区域独特性的线索吗? 相似文献
159.
我们通过监测位于亚平宁地区的一个粘土斜坡内正孔隙水压力来分析降水如何影响沿土体剖面的孔隙压力分布,从而影响斜坡稳定性。监测数据在监测滑坡活动的第一个季节(2001年8月-2002年6月)获得。研究地点位于一个复杂滑坡后缘,该处斜坡即将发生浅层滑坡,斜坡变形特征非常明显。
孔隙水压力数据的初步分析显示,过去11个月其变化呈现稳定的趋势。在寒冷潮湿的季节里,饱和带通常延伸到接近地表(小于1m)。孔隙水压力测量显示,任何条件下,整个斜坡内存存明显的垂直向下水流,但其在很大程度上受顺坡水流控制。与降雨对应,浅层地表(1—3m)存在压力脉冲,与低渗透性土体相比,其滞后过程很短,并且水流有瞬时水流的特征。斜坡在观察期问破坏,孔隙水压力的瞬时反应说明其为孔隙水压力型滑坡。
地下水流存在优势路径,这种现象可以解释在同样深度内一些传感器的异常反应。 相似文献
160.
Holdsworth C 《International journal of population geography : IJPG》1998,4(4):341-360
"This paper compares regional patterns of leaving home in Spain during the 1970s and 1980s based on analysis of the 1991 Spanish Sociodemographic Survey. The purpose of this analysis is to demonstrate that while nationally Spain is representative of a southern European pattern of leaving home, (i.e. relatively late and closely associated with partnership formation), there is considerable regional variation in timing, incidence and initial destinations on leaving home. These differences are explored using hazard rates of leaving home by destination and birth cohort for 11 Spanish regions." 相似文献