Relation of Pathways and Transit Times of Recharge Water to Nitrate Concentrations Using Stable Isotopes.   总被引：1，自引：0，他引：1  

Matthew K. Landon  Geoffrey N. Delin  Stephen C. Komor  Charles P. Regan 《Ground water》2000,38(3):381-395

  相似文献   

南黄海地区强震趋势预测   总被引：3，自引：0，他引：3       下载免费PDF全文

门可佩  李端 《地震工程学报》2000,22(2):134-138

对南黄海地区 1 846年以来MS≥ 6强震活动的可公度性进行了分析 .发现该区强震活动具有 6a、1 2a和 5 7a的基本周期 ,此外还有 6 3a、6 9a和 75a的周期 .根据强震活动的可公度性特征和丛集特征 ,对南黄海地区未来MS≥ 6地震活动趋势进行了预测 ,并对预测结果进行了论证 .  相似文献   

怀来等台固体潮观测调和分析结果   总被引：3，自引：3，他引：0  

陈德福  段立新  李玉  李晓军  宦吉洪  景树娟 《华北地震科学》2000,18(2):50-55

重点概述怀来台洞条件、项目手段及其监测功能后,公布其倾斜（ＳＱ－７０．ＦＳＱ）、应变（ＳＳＹ－Ⅱ）固体潮水平分量及全国部分体应变（ＴＪ－１Ａ）台站固体潮观测长系列调和分析结果,与国内外同类先进台站相比,怀来的固体潮观测精度已达到国际领先水平。  相似文献   

渤海海岸带变迁及其环境地质效应   总被引：7，自引：3，他引：4  

段永侯 《水文地质工程地质》2000,27(3):1-5

渤海海岸带变迁频繁。自第四纪以来,由于新构造活动与气候变迁,约有7～8次大规模海侵。渤海海岸带变迁对海岸带岩相古地理、海岸带地貌的形成演化、海岸带卤水矿床与贝壳堤分布、地质灾害的类型和强度、地下水流系统划分,起着重要的控制作用。  相似文献   

On the postprocessing removal of correlated errors in GRACE temporal gravity field solutions   总被引：9，自引：2，他引：7  

X. J. Duan  J. Y. Guo  C. K. Shum  W. van der Wal 《Journal of Geodesy》2009,83(11):1095-1106

We revisit the empirical moving window filtering method of Swenson and Wahr (Geophys Res Lett 33:L08402, 2006) and its variants, Chambers (Geophys Res Lett 33:L17603, 2006) and Chen et al. (Geophys Res Lett 34: L13302, 2007), for reducing the correlated errors in the Stokes coefficients (SCs) of the spherical harmonic expansion of the GRACE determined monthly geopotential solutions. Based on a comparison of the three published approaches mentioned, we propose a refined approach for choosing parameters of the decorrelation filter. Our approach is based on the error pattern of the SCs in the monthly GRACE geopotential solutions. We keep a portion of the lower degree-order SCs with the smallest errors unchanged, and high-pass filter the rest using a moving window technique, with window width decreasing as the error of the SCs increases. Both the unchanged portion of SCs and the window width conform with the error pattern, and are adjustable with a parameter. Compared to the three published approaches mentioned, our unchanged portion of SCs and window width depend on both degree and order in a more complex way. We have used the trend of mass change to test various parameters toward a preferred choice for a global compromise between the removal of the correlated errors and the minimization of signal distortion.  相似文献   

Similarity solution of oblique impact of wedge-shaped water column on wedged coastal structures     

W.Y. Duan  G.D. Xu  G.X. Wu 《Coastal Engineering》2009

The initial stage of plunging wave impact obliquely on coastal structures is analysed. The problem is modelled through an oblique collision of an asymmetrical water wedge and an asymmetrical solid wedge. The gravity effect on the flow is ignored based on the assumption that the ratio of the incoming speed of the wave to the acceleration due to gravity is much larger than the time scale of interest. Similarity solution method based on the velocity potential theory is then used. The problem of this similarity flow is solved by a boundary element method through the Cauchy theorem in the complex plan. Results for the wave elevation and pressure distribution are provided, including the forces and moments, effects of different impact angles and the effects of oblique impact are investigated. In particular, negative pressure near the tip of the solid wedge is observed and its implications are discussed.  相似文献   

Formation and early development of tetraspores of Polysiphonia urceolata (Rhodomelaceae, Rhodophyta)     

YAO Jianting  LI Dapeng  YU Shenhui  LIU Jidong  DUAN Delin 《中国海洋湖沼学报》2009,27(2)

Polysiphonia urceolata is one type of potential commercial red seaweeds used for breeding and cultivation, because of its significant biochemical and biomedical application. However, the information of breeding and seedling incubation for cultivation is limited, especially the early development. In this study, tetrasporohyte and gametophyte of P. urceolata were taken as the study materials in Huiquan Bay, Qingdao, China. The cleaned and sterilized tetrasporophytes and gametophytes were pre-cultured in sterilized seawater, then nurtured at 18℃, 25 μmol photons m-2 s-1 in 12:12 h (light:dark) photoperiod. Continuous observation under microscope showed that the early development consists of bipolar division stage and seedling stage. In the division stage, tetraspores germinate into bipolar sporelings that further differentiate into a colorless rhizoidal portion and a lightly pigmented upright shoot. The lightly pigmented rhizoidal cell develops to a rhizoid and the larger pigmented cell transforms to an erect axis. In the seedling stage, several quasi-protuberances appear on the erect axis and form juvenile seedlings. The results demonstrate the culture of P. urceolata from tetraspores under laboratory conditions.  相似文献   

Detecting the relationship between summer rainfall anomalies in eastern china and the SSTA in the global domain with a new significance test method   总被引：1，自引：0，他引：1  

Chuhan Lu  Zhaoyong Guan  Panxing Wang  Mingkeng Duan 《中国海洋大学学报(英文版)》2009,8(1):15-22

It is suggested that the multiple samples in a correlation map or a set of correlation maps should be examined with sig-nificance tests as per the Bernoulli probability, model. Therefore, both the contemporaneous and lag correlations of summertime pre-cipitation R in any one of the three regions of Northern China (NC), the Changjiang-Huaihe River Valley (CHRV), and Southern China (SC) with the SSTA in the global domain have been tested in the present article, using our significance test method and the method proposed by Livezey and Chen (1983) respectively. Our results demonstrate that the contemporaneous correlations of sum-mer R in CHRV with the SSTA are larger than those in NC. Significant correlations of SSTA with CHRV R are found to be in some warm SST regions in the tropics, whereas those of SSTA with NC R, which are opposite in sign as compared to the SSTA-CHRV R correlations, are found to be in some regions where the mean SSTs are low. In comparison with the patterns of the contemporaneous correlations, the 1 to 12 month lag correlations between NC R and SSTA, and those between CHRV summer R and SSTA show simi-lar patterns, including the magnitudes and signs, and the spatial distributions of the coefficients. However, the summer rainfall in SC is not well correlated with the SSTA, no matter how long the lag interval is. The results derived from the observations have set up a relationship frame connecting the precipitation anomalies in NC, CHRV, and SC with the SSTA in the global domain, which is criti-cally useful for our understanding and predicting the climate variabilities in different parts of China Both NC and CHRV summer R are connected with El Nino events, showing a'--'pattern in an El Nino year and a'+ +'pattern in the subsequent year.  相似文献   

基于拔桩能力的自升式平台海外作业优选     

宋林松  曹式敬  李军伟  段梦兰 《海洋地质译丛》2010,(4):106-110

针对某海外项目中可能遇到的钻井平台压载后入泥深度过大和拔桩困难的问题,开展平台优选计算。首先搜集了预定作业井位周围井位的地质勘查资料,利用二次插值法进行作业井位地质勘察数据计算,据此计算了桩脚入泥深度,并根据作业平台结构参数计算了平台的拔桩阻力。为解决平台极限拔桩能力小于拔桩阻力的问题,设计了可控冲桩阀和冲桩系统以消除或减小桩靴底部的吸附力、桩靴侧部土体剪切力和桩靴上部土重。最后将平台拔桩能力与最终拔桩阻力进行对比,给出平台推荐结果。  相似文献   

两形态类型织纹螺(Nassarius)的鉴定   总被引：3，自引：2，他引：1  

李海涛  张敬怀  董燕红  方宏达  林端  李秀芹  欧强 《海洋与湖沼》2008,39(4)

在整理广东珠海高栏岛潮下带的螺类样品时,发现两不同形态类型的织纹螺,一类型鉴定为西格织纹螺（Nassarius siquijorensis）,另一类型与前者在内唇和外唇形态上存在明显差异但其他特征基本相同。比较了两类型个体的齿舌形态,并对选取的5个个体的COⅠ基因序列进行了研究。结果表明,两类型个体的齿舌形态基本一致,齿列数53—66排,中央齿上缘小齿8—12枚;COⅠ基因序列存在较大的变异,709bp的DNA片段上共有40个位点变异,其中38个变异位点为密码子第三位碱基,个体间的碱基差异在2—35bp之间;贝壳变异与DNA变异不存在关系,同类型的个体在DNA序列上差异较大,不同类型个体的差异却极小;在基于COⅠ基因序列构建的系统树中两类型的个体明显聚为一支。依据5条COⅠ基因核苷酸序列推导的氨基酸残基序列完全相同。齿舌形态和分子生物学证据都证实两种类型的个体同属于西格织纹螺。  相似文献