矩形明槽宽深比和边壁糙率对于流速分布和阻力影响的实验研究

本文通过矩形水槽试验,改变宽深比和边壁糙率,系统地研究了明渠恒定均匀流水力学特性.试验表明,根据断面上各条垂线流速分布的特征,可将断面划分为对数流速分布区和抛物线流速分布区.文中给出了两区流速分布的表达式以及两区分界线和垂线最大流速点位置随宽深比和边壁糙率而变化的规律.本文还分析了光滑明渠流和粗糙明渠流阻力系数的变化、阻力系数的分割以及剪切应力沿床面和边壁的分布规律.     

Relations between climatic variability and hydrologic time series from four alluvial basins across the southwestern United States

Hydrologic time series of groundwater levels, streamflow, precipitation, and tree-ring indices from four alluvial basins in the southwestern United States were spectrally analyzed, and then frequency components were reconstructed to isolate variability due to climatic variations on four time scales. Reconstructed components (RCs), from each time series, were compared to climatic indices like the Pacific Decadal Oscillation (PDO), North American Monsoon (NAM), and El Niño-Southern Oscillation (ENSO), to reveal that as much as 80% of RC variation can be correlated with climate variations on corresponding time scales. In most cases, the hydrologic RCs lag behind the climate indices by 1–36 months. In all four basins, PDO-like components were the largest contributors to cyclic hydrologic variability. Generally, California time series have more variation associated with PDO and ENSO than the Arizona series, and Arizona basins have more variation associated with NAM. ENSO cycles were present in all four basins but were the largest relative contributors in southeastern Arizona. Groundwater levels show a wide range of climate responses that can be correlated from well to well in the various basins, with climate responses found in unconfined and confined aquifers from pumping centers to mountain fronts.     

热力作用对烃源岩中重排藿烷类化合物形成的作用

通过对87个采自鄂尔多斯盆地煤系烃源岩和松辽盆地湖相烃源岩样品进行的地球化学分析结果显示,热力作用对烃源岩重排藿烷组成特征的影响强烈。随成熟度的变化,来自两套沉积体系的烃源岩中重排藿烷相对丰度的分布相似,随成熟度增大17α（H）-重排藿烷和18α（H）-新藿烷相对丰度均先增大后减小,并在R_o:0.80%~0.90%（生油窗）时达峰值。不同沉积环境的烃源岩中重排藿烷的成熟度与绝对浓度的变化规律一致。在R_o:0.50%~0.70%（未熟-低熟）阶段,重排藿烷绝对浓度较大;在R_o:0.70%~0.80%（成熟）阶段,重排藿烷的绝对浓度显著降低。不同沉积环境中重排藿烷的参数随成熟度的变化规律揭示:在重排藿烷的形成过程中,热力作用的影响要强于沉积环境和生物来源。     

人工震源地下介质变化动态监测

成像地球内部介质结构及其动态变化是地球物理学家的主要任务.相对于对地球介质静态结构的认识,对于地下介质性质随时间变化的了解明显不足.近年来随着观测资料的增加,已经开始利用重复地震和噪声等震源研究地下介质变化.受到源位置和时间等因素制约,基于地震和噪声等被动震源的观测结果的时间和空间分辨率有限.利用人工震源主动向地下发射...     

青海省海西州德令哈地区近千年来年降水量变化特征分析

试图揭示位于我国青藏高原东北部的青海省海西州德令哈地区近千年来世纪尺度年降水量变化规律。分析结果表明,该地区近千年年降水量变化存在显著的多尺度周期变化特征,其中以13～18世纪中的200年主控周期最为明显,并在15～17世纪达到最强,而近200年则以准120年的周期振荡为主,且在19世纪两种主要周期变化趋势相反,在近百年又趋向一致。年降水量序列的均值突变一般以30～100年尺度最为明显,世纪尺度的均值突变时段分别为公元1100～1111年、1403～1449年及1615～1661年,表现为年降水量的减少,以及公元1321～1348年、1497～1557年、1728～1743年及1885～1891年,表现为年降水量的增加。200年以上时间尺度的方差突变主要表现为序列的低频变化幅度,从公元1220年前后至1580年前后持续增大,且以15世纪的方差突变最为明显。     

西北地区晚第四纪沉积地层一元正脂肪酸酰胺分布特征及古气候意义

利用气相色谱质谱联用仪在中国西北地区晚第四纪沉积地层中检测出一类特殊的类脂物分子--一元正脂肪酸酰胺.根据其碳数分布特征及前人的研究成果,认为一元正脂肪酸酰胺来源于各种生物体,产生于生物的某些生理活动过程,而不是来源于石油残余物及各种可能的污染.通过对比3个不同区域相近时期古湖相及黄土沉积地层中的脂肪酸酰胺分布特征,认为柴达木盆地可能不是黄土沉积的主要物源区,而额济纳盆地及邻近区域对黄土堆积有着重要的贡献或具有相同的物源.典型黄土沉积地层中UFAA值(不饱和与饱和脂肪酸酰胺相对含量的比值)与粒度、磁化率等指标具有很好的可对比性,特别是在相对暖湿阶段UFAA值呈现了明显的低值.这一现象表明脂肪酸酰胺在沉积地层中的变化受控于气候变化所导致的成岩作用强度的变化,从而记录了气候变化信息.通过研究,认为生物生理活动过程中所产生的一元正脂肪酸酰胺与构成细胞膜的类脂物分子一样,可记录古气候变化.     

Long-term seismotectonic influence on the hydrochemical composition of a spring located at Koryaksky-Volcano, Kamchatka: deduced from aggregated earthquake information

The analysis of earthquake-related signals in hydrochemical time series is still a challenging task. Mostly it is unclear how the geometrical and energetic distribution of earthquakes is influencing variation in the hydrochemical composition of monitoring sites, e.g. located close to volcanoes. Past research showed that linear stress-release models alone are not capable to explain sufficiently observed variation in hydrochemical time series due to earthquake activity. A spring located at the base of Koryaksky Volcano, which has shown hydrochemical variation close to 5, major earthquakes, was chosen to analyse relation patterns between hydrochemical variation and seismicity. A possible mechanism, explaining observed hydrochemical variation, that seismic waves trigger an underground water pumping caused by nucleation of gas bubbles in magma was proposed. Consequences are an increase of discharge, gas content in water and changes in the mixing ratios of waters of different genesis. Based on functions of aggregated earthquake information (E) it is herein shown that seismotectonic-triggered processes have a significant influence on the variation of the hydrochemistry of the spring, lasting longer than two decades. At least seven categories of relation patterns between hydrochemical variation and seismotectonic activity E can be identified. A conducted spectral analysis shows that earthquake activity and hydrochemistry share spikes in frequencies. Results prove that the use of functions of transformed aggregated seismic observations is useful to represent the seismotectonic activity for analysing earthquake-related signals in hydrochemical time series.     

Singular spectral analysis of homogeneous Indian monsoon (HIM) rainfall

Homogeneous Indian Monsoon region rainfall for the epoch 1871–1990 has been analysed using Singular Spectral Analysis. It is shown that the HIM time series is simple in structure with only the annual oscillation and its first two harmonics accounting for almost the entire variability. Longer period oscillations related to lunar tidal forcing, solar activity and quasibiennial variation are conspicuously absent. It is also shown that the singular spectral decomposition is closely similar to complex demodulation and thus provides variations in the signals which evolve only slowly with time. As the rainfall series is marked by several jerky changes, predictability of HIM rainfall through the principal components derived from SSA appears impossible.     

Correlation and migration studies of North Central Sumatra oils

The Central Sumatra Basin (CSB) is a prolific petroleum-producing basin and its petroleum systems have been extensively studied. The widely occurring Tertiary lacustrine shale, Brown Shale, has long been recognized as the main source rock for tens of billions of barrels of oil in place. The oils produced from different fields display significant variation in source characteristics that have been attributed to variation in source facies. Despite this generalized recognition of the oil source, the links between major oil accumulations and many possible source kitchens throughout the basin have not been established as detailed oil-source correlation, and oil migration routes are not well defined. For continued exploration in the region, detailed genetic grouping and migration routes of the oils were evaluated through geochemical characterization of numerous oils from various fields in the northern part of Central Sumatra. Biomarker and carbon isotopic data indicate that the oils are quite similar geochemically but form several genetic groups on the basis of subtle but persistent differences in source facies. The groupings appear geographically meaningful and show association of the different oil groups with various troughs. Carbazole distributions show consistency in suggesting differences in relative migration distance among the oils within each genetic group. By combining the oil grouping and carbazole distributions with geological data, models of migration directions and pathways for oils in North Central Sumatra have been constructed.     

The influence of seismotectonics on precursory changes in groundwater composition for the 1995 Kobe earthquake, Japan

It is shown that temporal variation in hydrochemistry may be attributed, in part, to continuous seismotectonic activity occurring before the onset of the 1995 “Kobe” earthquake, Japan, challenging the “one earthquake–one signal” hypothesis with respect to potential precursory signals to this devastating event. A possible continuous seismotectonic influence on chloride and sulphate ion-concentration is evaluated with aggregate earthquake-information by transforming a multivariate earthquake time series (including coordinates and magnitude) into a one-dimensional time series (considering geometric relationships between earthquakes and the well-site). A piecewise analysis of ion-concentration and seismotectonic-activity time series compares trends and change points between the two time series: a positive correlation (before the proposed onset of the preparation stage) is followed by a negative correlation (during the proposed preparation stage) which, in turn, is succeeded by a positive correlation (after the heaviest aftershock sequences). This suggests that seismotectonic processes occurring before the Kobe earthquake dynamically influenced aquifer characteristics, leading to temporal variations in the hydrochemical time series. Accordingly, a dynamic change in the mixing ratios of waters with different hydrochemical characteristics is proposed as a mechanism for explaining observed variation. The research can be extended by considering vectors in the stress field that lead to changes in the aquifer-well system.The influence of seismotectonics on precursory changes in groundwater composition for the 1995 Kobe earthquake, Japan.     

柴达木盆地西部第三系咸水湖相原油地球化学特征

在系统分析柴达木盆地西部各油田40余个原油样品碳同位素和饱和烃、芳烃组成的基础上,全面剖析了该地区第三系湖相原油的地球化学特征.研究结果表明,这些原油具有特殊的碳同位素组成和异常的生物标志物分布.其全油碳同位素偏重(-26‰～-24‰);正构烷烃系列单体烃碳同位素分布曲线呈水平状,表现出类同于海相有机质的碳同位素组成特征.它们的生物标志物中正烷烃系列兼具奇碳和偶碳优势双重碳数分布模式;呈强植烷优势,Pr/Ph值大多<0.6;伽玛蜡烷普遍异常丰富,C35藿烷含量高,表征高盐、厌氧的咸水湖相沉积环境性质.芳烃组份以萘、菲系列为主,而二苯并噻吩等含硫有机化合物相对含量较低,反映该地区咸水湖相原油源岩沉积相的特殊性.柴西各油田原油地球化学参数在区域上呈规律性变化趋势,与其源岩沉积相的时空变迁相一致.     

基于遗传熵谱估计的年径流周期识别

为识别年径流量序列的隐含周期,提出基于加速遗传算法的熵谱估计算法,与传统的方差谱和Burg谱相比,该方法由熵谱分析的4个等价条件构建多目标函数,并以加速遗传算法作为优化算法,谱估计结果不依赖于初始值的选取,对数据长度、信噪比和初相位有较强的适应性。在三川河流域后大成站1956-2000年径流量序列周期识别中的应用结果表明,在95%的置信检验水平下,序列中存在着12.29年和2.67年的显著隐含周期,为三川河流域年径流的变化规律和变化的阶段性研究提供了一条新的定量研究手段。     

The primitive lavas of Roccamonfina volcano,Roman region,Italy: new constraints on melting processes and source mineralogy

Within a large collection of lavas from the Roccamonfina volcano are rocks which represent the most mafic samples yet recorded from Roccamonfina and which are amongst the least differentiated lavas found in the Roman co-magmatic region as a whole. These rocks extend both high-K and low-K series to more primitive values. However, petrographic and geochemical considerations rule out a primary origin, and even these mafic samples appear to record the effects of repeated episodes of fractional crystallization and hybridization. Relatively potassic samples from the low-K series are apparently transitional between low-K and high-K series, as previously delineated. However, these intermediate-K samples are not transitional in their Sr isotopic composition, suggesting that there is no continuum between low-K and high-K magma source regions. Rather, the compositional range within the low-K series appears predominantly to reflect variation in the degree of melting of a common mantle source. Analysis of the low-K series data, using an inverse method suggests a source containing amphibole and garnet, and indicates that these phases were consumed during the melting processes responsible for the low-K series magmas. The role of amphibole is further indicated by the association of low K₂O with elevated Rb concentration and, for example, higher Ce/Yb. Such variations are taken to reflect the consumption of high K/Rb amphibole during the initial phase of partial melting.     

'Clean' spectral analysis of long-term sea-level changes

A new ‘clean’ spectral technique has been applied, for the first time, to analyse a record of long-term sea-level fluctuation during the last 200 million year (Myr). The technique is based on a one dimensional complex deconvolution algorithm and removes the effects of the data sampling as well as the artifacts arising from the choice of data window. The analysis reveals a dominant periodicity of 33 Myr in the sea-level variations. This periodicity compares well with the known half-period of the Sun's oscillation perpendicular to the galactic plane. Interestingly, a 33 Myr periodicity can also be correlated with the reported mass extinction cycles and other geological periodicities. The results suggest galactic forcing as a possible driving mechanism for quasi-periodic terrestrial processes.     

Properties of oscillations in sunspot penumbras

Observations of oscillations in the penumbras of seven sunspots are analyzed. High-sensitivity differential measurements of the line-of-sight velocity (11 time series) and variations of the Ni I 4857 Å and H_β line profiles (four series) have provided new data making it possible to improve estimates of the amplitude and spectral characteristics of the oscillations. In the middle penumbras, oscillations of the line-of-sight velocity with fundamental periods of 5 and 8–10 min predominate at the photospheric level; their amplitude does not exceed 40–50 m/s, and the spatial coherence scale in the radial direction is no greater than 5″–10″. At frequencies of 0.5–2.0 mHz, the phase difference between the photosphere and chromosphere (NiI 4857 Å-H_β) is close to 180°. The line-of-sight velocity component due to Evershed motions is responsible for oscillations with periods of 15–35 min, which occur synchronously at both heights.     

Variability of stars in the Pulkovo spectrophotometric catalog

We present the results of a statistical study of brightness variability for 693 stars of the Pulkovo spectrophotometric database in five spectral bands in the range λλ 320–1080 nm. Significant brightness variations were detected in at least one spectral band against the background of the random noise for one-third of the stars not earlier believed to be variable. A comparison of the distributions of these variations in amplitude and spectral band for the normal and variable stars shows that variability is inherent to most stars to some extent and is often wavelength dependent.     

Hydrocarbons in Mississippi Fan and intraslope basin sediments

Aliphatic and aromatic hydrocarbons in sediments of the middle and lower Mississippi Fan and two intraslope basins in the Gulf of Mexico are derived from terrestrial organic matter and thermogenic, mature hydrocarbons. The terrestrial hydrocarbon component consists primarily of terrigenous, plant biowaxes (n-alkanes with 21 to 33 carbons). The occurrence of thermogenic hydrocarbons in immature near-surface sediments, their molecular distributions and concentration variations with depth suggest that the majority of these mature hydrocarbons have migrated from a source much deeper in the sediment column. A portion of the thermogenic hydrocarbons may be derived from recycled material and includes phenanthrene, methyl phenanthrenes, chrysene and benzopyrenes. The migrated, thermogenic hydrocarbons include normal and isoprenoid alkanes with less than 21 carbons, naphthalene, methyl naphthalenes, ethyl naphthalenes and other aromatics of similar volatility (i.e., biphenyl, acenaphthene and fluorene). Triterpane, sterane and aromatized sterane distributions suggest that the thermogenic hydrocarbons at both sites have a common source and are overprinted with immature sediment hydrocarbons. The biomarker distributions and carbon isotopic compositions of the thermogenic hydrocarbons are atypical for petroleum produced in the Gulf of Mexico. Molecular distributions of the hydrocarbons are constant, regardless of the present depth of occurrence, suggesting that they have migrated in a separate phase. The upward migration of hydrocarbons from deeper sources is a wide-spread phenomenon in the Gulf of Mexico with several documented cases of massive seepage (visible oil) as well as the more diffuse permeation of Pleistocene sediments of the Mississippi Fan and two intraslopes reported here.     

水灰岩地层中子随能量和时间分布的Monte Carlo模拟

作者在MCNP的基础上，开发了中子测井，中子通量随空间、能量、时间分布蒙特卡罗（Monte Carlo)模拟软件包。对裸眼井、井眼里无下井仪器、水饱和灰岩地层、井眼注水，用该软件计算了沿井轴和沿井壁中子能量随能量、时间分布，以及沿井轴和沿井壁热中子和超热中子时间谱。即源距离变化对中子能量随能量、时间分布和井轴与井壁热中子、超热中子时间谱的影响。     

变化环境下石羊河流域年径流频率计算

受气候变化与人类活动的影响,水文序列一致性遭到破坏,传统的频率计算方法受到挑战。针对石羊河流域8条河流年径流量序列,在基于水文变异诊断系统进行变异分析的基础上,采用条件概率分布法和混合分布法进行了变化环境下的年径流频率计算。结果表明,石羊河流域年径流量序列以向下跳跃变异为主,变异年份多集中在1960年附近;变异序列的两种分布均通过K-S检验,最优分布的拟合效率系数均大于0.97;对比由考虑变异的理论分布与不考虑变异的一致性P-III型分布确定的设计年径流量,当设计频率高于90%时,大靖河与西营河的设计年径流量值相差较大。因此,石羊河流域新建水利工程的规划设计,应适当考虑水文资料的变异特性,选择合理的频率分析方法确定设计年径流量。     

The effect of source material,rock type and diagenesis on the n-alkane content of sediments

The effects of diagenesis on marine organic material have been compared to those on terrestrial organic material in three Australian oil exploration wells. n-Alkaae distributions obtained for limestones ranged from C₁₅ to C₂₅ with no odd-even predominance and showed little variation with depth. n-Alkane distributions obtained for shales ranged from C₁₅ to C₃₃ and frequently had a pronounced odd-even predominance. Differences in the rates of hydrocarbon diagenesis between different rock types may be due to variations in either clay mineral content or the nature of the parent organic material. The individual n-alkane distributions of the sediments are determined by source material, degree of diagenesis and lithofacies.