共查询到20条相似文献，搜索用时 31 毫秒
1.
Properties of iron at the Earth's core conditions 总被引：2，自引：0，他引：2
Orson L. Anderson 《Geophysical Journal International》1986,84(3):561-579
Summary. The phase diagram of iron up to 330 GPa is solved using the experimental data of static high pressure (up to 11 GPa) and the experimental data of shock wave data (up to 250 GPa). A solution for the highest triple point is found ( P = 280 GPa and T = 5760 K) by imposing the thermodynamic constraints of triple points. This pressure of the triple point is less than the pressure of the inner core–outer core boundary of the Earth. These results indicate that the density of iron at the inner core–outer core boundary pressure is close to 13 g cm−3 , which lies close to the seismic solutions of the Earth at that pressure. It is thus concluded that the Earth's inner core is very likely to be virtually pure iron in its hexagonal close packed (hcp) phase.
It is shown that four properties of the Earth's inner core determined from seismology are close in value to the corresponding properties of hcp iron at inner core conditions: density, bulk modulus, longitudinal velocity, and Poisson's ratio. The density–pressure profile of hcp iron at inner core conditions matches the density–pressure profile of the inner core as determined by seismic methods, within the spread of values given by recent seismic models.
This indicates that the Earth is slowly cooling, the Earth's inner core is growing by crystallization, and the impurities of the core are concentrated in the outer core. The calculated temperature at the Earth's centre is 6450 K. 相似文献
It is shown that four properties of the Earth's inner core determined from seismology are close in value to the corresponding properties of hcp iron at inner core conditions: density, bulk modulus, longitudinal velocity, and Poisson's ratio. The density–pressure profile of hcp iron at inner core conditions matches the density–pressure profile of the inner core as determined by seismic methods, within the spread of values given by recent seismic models.
This indicates that the Earth is slowly cooling, the Earth's inner core is growing by crystallization, and the impurities of the core are concentrated in the outer core. The calculated temperature at the Earth's centre is 6450 K. 相似文献
2.
围绕核心城市组织的合理的区域分工体系是都市圈功能整合、和谐运作,发挥其空间组织优势的关键,而良好的区域分工往往以城市间职能的互补性为基础。采用对应分析方法,应用SPSS生成点聚图并计算反映职能互补性的统计量——总惯性,对1997年和2007年京津冀、长三角、珠三角三大都市圈核心城市的职能分工体系特征、格局以及职能互补性进行比较研究。结果显示,10 a间各都市圈以服务业职能为主的一般化职能开始分化,高端服务业职能逐步由一般化职能转变为专业化职能,并且向都市圈的中心城市集中。工业制造业职能在京津冀和长三角都市圈由一般化职能转变为专业化职能,在珠三角都市圈刚好相反。同时,工业制造业职能的分工格局在三大都市圈表现出不同的变化趋势。分工体系特征反映出三大都市圈不同的分工格局,京津冀、珠三角表现出双中心结构的分工格局,而长三角则是单中心结构的分工格局。对核心城市职能互补性的分析显示,京津冀潜在的职能互补性在三大都市圈中是最高的,但是由于产业梯度过大、区域协调机制不够完善等原因,互补性优势并未得到很好的发挥。 相似文献
3.
M. Horrocks W. T. Baisden J. Flenley D. Feek L. González Nualart S. Haoa-Cardinali T. Edmunds Gorman 《Journal of Paleolimnology》2012,48(4):767-783
Previous paleoenvironmental records from the lake of Rano Raraku crater, Easter Island??s statue quarry, showed evidence of two major environmental changes, fluctuating lake levels and Polynesian forest clearance. There have been no reports, however, of former shorelines and it is not known if deforestation of the crater was for quarrying alone, or also for agriculture. We shed light on this by examining macrofossil casts of plants found in dryland iron pan deposits, and using combined analyses of pollen, phytoliths and starch in a lake sediment core and dryland soil profile. Casts of wetland taxa, namely Scirpus californicus and fern rhizomes, were identified in the iron pan deposits up to ~10?m above the current lake level, providing evidence of higher lake level during the last Glacial period. This height is near the level of the col on the western side of the crater, indicating that the lake was at its maximum possible elevation at the time, with overflow via the col. Microfossils of introduced Colocasia esculenta (taro), Ipomoea batatas (sweet potato), Musa (banana sp.) and possibly Lagenaria siceraria (bottle gourd) were identified in the core and soil profile, providing evidence of ancient Polynesian agriculture. Earliest evidence of gardening occurs at ~627?C513?cal BP, immediately after large-scale forest clearance. The core and soil profile were located on opposite sides of the catchment, suggesting that the crater was intensively multi-cropped and that widespread irrigated gardens co-existed with statue-quarrying activity. 相似文献
4.
采用微生物宏基因组学微阵列GeoChip 5.0技术，选择腾格里沙漠东南缘沙坡头地区不同年代人工固沙植被区的生物土壤结皮（BSC）为对象，分析BSC演替过程中参与铁代谢的功能微生物组成及其功能基因变化特征，研究微生物铁代谢对BSC演替的响应及调控。结果表明：真菌参与铁吸收和转运过程，古菌参与铁转运和贮存过程，细菌则在铁代谢吸收、转运和贮存过程中均起主要调控作用。门水平上，BSC铁代谢功能微生物组成变化对演替的响应不敏感，BSC铁代谢微生物主要为变形菌门（Proteobacteria）。BSC铁代谢功能基因多样性的显著提高和三类铁代谢过程基因信号强度达到最高水平需要经过61 a的演替。调控BSC铁吸收过程的主要功能基因为亚铁氧化酶编码基因iro；调控原核生物铁转运过程的主要功能基因，为羟基苯甲酰丝氨酸铁外膜转运体编码基因cirA和Fe（Ⅱ）转运蛋白编码基因feoB，真菌铁转运过程主要依靠含铁细胞转运体和铁氧化酶高亲和力的作用；调控铁贮存过程的主要功能基因为固定相类核蛋白编码基因dps。在BSC演替阶段末期，上述铁代谢功能基因强度的显著增加促进了微生物的铁代谢潜能。干旱、半干旱荒漠生态系统植被恢复过程中微生物铁代谢潜能的恢复需要较长时间。 相似文献
5.
RENé HENRION 《地理学报(英文版)》1993,(6)
In contrast with conventional PCA,a direct superposition and joint interpretation of loading plots is notpossible in three-way PCA,since there may be data variance which is described by unequal componentsof different modes.The contributions to variance of all possible combinations of components aredescribed in the core matrix.Body diagonalization,which is achieved by appropriate rotation ofcomponent matrices,is an essential tool for simplifying the core matrix structure.The maximum degreeof body diagonality which may be obtained from such transformations is analysed from both themathematical and simulation viewpoints.It is shown that,at least in the average case,high degrees canbe expected,which makes the procedure reasonable for many practical applications.Furthermore,simulation as well as theoretical derivation show that the success of body diagonality depends on the so-called polarity of the core array.The methodology is illustrated by a three-way data example fromenvironmental chemistry. 相似文献
6.
以往研究对于距离在网络外部性影响城市功能过程中的作用所知甚少,而且多关注城市网络外部性的正面效应,对城市间竞争以及由此所带来的网络外部性的负效应缺少分析。为了弥补已有研究的不足,本文采用空间的视角,以城市群内的城市生产性服务功能为例,建立一个核心-外围的空间结构来揭示城市生产性服务功能、网络外部性与地理距离之间的关系。研究发现：① 城市生产性服务功能强度随着远离城市群核心城市而上升,互联网渗透率和列车网络中心度会显著地强化这一效应;② 城市生产性服务功能随距离变化的机制在于竞争效应比协同效应对地理距离更加敏感,从而衰减更快,因而靠近核心城市的城市在生产性服务功能上遭受了“集聚阴影”,而远离核心城市的城市在功能上更多的受到了协同作用的支撑。本文结论为推进城市群内的分工协作与一体化发展提供了重要启示。 相似文献
7.
Peter Olsen 《Geophysical Journal International》1977,51(1):183-215
This paper investigates possible long-period oscillations of the earth's fluid outer core. Equations describing free oscillations in a stratified, self-gravitating, rotating fluid sphere are developed using a regular perturbation on the equations of hydrodynamics. The resulting system is reduced to a finite set of ordinary differential equations by ignoring the local horizontal component of the earth's angular velocity vector, Ω, and retaining only the vertical component. The angular dependence of the eigensolutions is described by Hough functions, which are solutions to Laplace's tidal equation.
The model considered here consists of a uniform solid elastic mantle and inner core surrounding a stratified, rotating, inviscid fluid outer core. The quantity which describes the core's stratification is the Brunt—Väisälä frequency N , and for particular distributions of this parameter, analytical solutions are presented. The interaction of buoyancy, and rotation results in two types of wave motion, the amplitudes of which are confined predominantly to the outer core: (1) internal gravity waves which exist when N2 > 0, and (2) inertial oscillations which exist when N 2 <4Ω2 . For a model with a stable density stratification similar to that proposed by Higgins & Kennedy (1971), the resulting internal gravity wave eigenperiods are all at least 8 hr, and the fundamental modes have periods of at least 13 hr. A model with an unstable density stratification admits no internal gravity waves but does admit inertial oscillations whose eigenperiods have a lower bound of 12hr. 相似文献
The model considered here consists of a uniform solid elastic mantle and inner core surrounding a stratified, rotating, inviscid fluid outer core. The quantity which describes the core's stratification is the Brunt—Väisälä frequency N , and for particular distributions of this parameter, analytical solutions are presented. The interaction of buoyancy, and rotation results in two types of wave motion, the amplitudes of which are confined predominantly to the outer core: (1) internal gravity waves which exist when N
8.
V. Dehant M. Feissel P. Defraigne F. Roosbeek J. Souchay 《Geophysical Journal International》1997,130(2):535-546
The observed time-series of precession/nutation show residuals with respect to an empirical model based on the rigid Earth theoretical nutations and a frequency dependent transfer function with resonances to the Earth's normal modes. These residuals display energy mainly in the frequency domain around 430 and 500 days in the inertial frame. In this frequency band, the energy is possibly related to two normalmode frequencies: the free core nutation (FCN) and the free inner core nutation (FICN). In this paper, we examine the possibility of obtaining this energy from the resonance effect induced by a luni-solar (or planetary) forcing, or by an atmospheric forcing at a frequency very close to these Earth free nutations. The amplification factor due to the resonance is computed from an analytical formula expressed in the case of a simplified three-layer ellipsoidal rotating earth (with an elastic inner core, a liquid outer core and an elastic mantle), as well as the empirical formula based on the analysis of VLBI observations. For the tidal forcing, the theoretical results do not show any resonance at the level of precision we have examined but it is still possible to find one frequency near the FCN or FICN frequencies which could be excited. In contrast, for the atmospheric pressure the level of energy needed could be obtained from the diurnal pressure, depending on the noise level of the Earth's global pressure. We also show that the combination of three waves can explain the observed decrease of energy with time. While the tidal potential amplitudes are too small, a pressure noise level of 0.5 Pa would be sufficient to excite these waves. 相似文献
9.
Geochemical signatures of two different coastal depositional environments within the same catchment 总被引：1，自引：0，他引：1
The geochemistry of lake (Renstradträsket) and estuarine (Pieni Pernajanlahti Bay) sediment was investigated in a medium sized watershed draining to the Gulf of Finland, Baltic Sea. Catchment land-use types were compared and found similar. Sediment cores were dated using 210Pb- and 137Cs-chronologies and analyzed for Al, K, Cu, Zn, Fe, Mn, phosphorus fractions, TN, TC and biogenic silica (BSi). Differences between the sediment cores were studied by using linear regression analysis and principal components analysis (PCA). Despite similarities in catchment land-use and history, the sediment geochemical profiles of the sites varied significantly. Some of the differences could be related to differences in chemical sedimentation environment (lacustrine versus estuarine). TP concentration was found to be positively correlated with sediment iron content in estuarine sediment but negatively correlated with Fe in lake sediment. In the estuarine core sedimentary iron was not correlated to lithogenic potassium and aluminum but in the lake core the iron seemed to be lithogenic in origin, as suggested by the strong positive correlations (r 2 = 0.95–0.96) between these three variables. Most similarities among the cores were found in Al concentrations. Estuarine nutrient profiles appeared relatively monotonous compared to the lake core. This is probably due to more vigorous mixing of the sediments that may ensure more rapid and complete consumption of the organic matter deposited on the bottom of the estuary. Therefore the lake sediment appeared to preserve the historical record of eutrophication better. Biologically less active and more particle-bound materials like the trace metals Cu and Zn seemed to retain good records of anthropogenic impact also in the estuarine core. The study highlights the need to take the sedimentation environment into account when interpreting geochemical record. 相似文献
10.
A simple quasi-empirical model is presented to calculate the deformation rate and age scale corresponding to ice core depth, where grain size and shape are determined only by grain growth and grain deformation processes. Given the size and elongation of grains as a function of ice core depth and the accumulation rate at the ice-sheet surface, it is possible to determine the ice core age scale. The model results are in good agreement with measured values of the rate of grain deformation and the age scale for the GIPS2 ice core at depths above 700 m. 相似文献
11.
Mineral resource classification plays an important role in the downstream activities of a mining project. Spatial modeling of the grade variability in a deposit directly impacts the evaluation of recovery functions, such as the tonnage, metal quantity and mean grade above cutoffs. The use of geostatistical simulations for this purpose is becoming popular among practitioners because they produce statistical parameters of the sample dataset in cases of global distribution (e.g., histograms) and local distribution (e.g., variograms). Conditional simulations can also be assessed to quantify the uncertainty within the blocks. In this sense, mineral resource classification based on obtained realizations leads to the likely computation of reliable recovery functions, showing the worst and best scenarios. However, applying the proper geostatistical (co)-simulation algorithms is critical in the case of modeling variables with strong cross-correlation structures. In this context, enhanced approaches such as projection pursuit multivariate transforms (PPMTs) are highly desirable. In this paper, the mineral resources in an iron ore deposit are computed and categorized employing the PPMT method, and then, the outputs are compared with conventional (co)-simulation methods for the reproduction of statistical parameters and for the calculation of tonnage at different levels of cutoff grades. The results show that the PPMT outperforms conventional (co)-simulation approaches not only in terms of local and global cross-correlation reproductions between two underlying grades (Fe and Al2O3) in this iron deposit but also in terms of mineral resource categories according to the Joint Ore Reserves Committee standard.
相似文献12.
Lucien von Gunten Christian Kamenik Marian Fujak Roberto Urrutia 《Journal of Paleolimnology》2012,47(4):583-600
Lake sediment records are underrepresented in comprehensive, quantitative, high-resolution (sub-decadal), multi-proxy climate
reconstructions for the past millennium. This is largely a consequence of the difficulty of calibrating biogeochemical lake
sediment proxies to meteorological time series (calibration-in-time). Thanks to recent methodological advances, it is now
possible. This paper outlines a step-by-step, specifically tailored methodology, with practical suggestions for calibrating
and validating biogeochemical proxies from lake sediments to meteorological data. This approach includes: (1) regional climate
data; (2) site selection; (3) coring and core selection; (4) core chronology; (5) data acquisition; and (6) data analysis
and statistical methods. We present three case studies that used non-varved lake sediments from remote areas in the Central
Chilean Andes, where little a priori information was available on the local climate and lakes, or their responses to climate
variability. These case studies illustrate the potential value and application of a calibration-in-time approach to non-varved
lake sediments for developing quantitative, high-resolution climate reconstructions. 相似文献
13.
J. P. Poirier 《Geophysical Journal International》1986,85(2):315-328
Summary . Dislocation theories of melting provide a possibility of calculating the melting temperature, from first principles, as the temperature at which the free energy of a crystal saturated with dislocations becomes equal to that of the dislocation-free crystal. After a brief review of the physical bases of the dislocation melting theories, Ninomiya's theory is used to determine the melting temperature as well as the volume and entropy of melting and the slope of the melting curve for iron at atmospheric pressure and under conditions prevailing at the Earth's inner core boundary. The necessary parameters (elastic moduli, Grüneisen parameter) are drawn from seismological earth models. We find a melting temperature of the material of the inner core of about 6150 K, independent of shock-wave experiments but in good agreement with them and with extrapolations using Lindemann's law. With usually accepted values of the melting point depression due to light elements in solution, the temperature at the inner core boundary is found to be T ICB ≅ 5000 K. This temperature is compatible with a temperature of the outer core at the core-mantle boundary T CMB ≅ 3800 K. Dislocation melting theories can thus help constrain the temperature profile in the Earth's core. 相似文献
14.
长江经济带乡村功能区域差异及类型划分 总被引：2，自引：0，他引：2
深度挖掘乡村功能价值是实现乡村全面振兴的重要途径,论文通过构建乡村功能综合评价指标体系,运用GIS和泰尔指数,揭示了2016年长江经济带130个市(区)乡村“生产-生活-生态”功能地区差异特征和差异来源,并进行功能分区。研究结果显示：① 长江经济带乡村功能具有显著的空间分异特征,农业生产功能强的区域集中在中游和下游平原地区;人居生活功能强的区域集中在下游省会及核心发展城市周边;生态保育功能强的区域在上游和中游山地丘陵地区。② 乡村功能总体区域差异来源于上、中、下游地区内部差异,农业生产功能在上游内部区域差异显著,人居生活功能和生态保育功能在下游内部区域差异显著,中游地区乡村功能整体区域差异较小。③ 基于研究结果将研究区划分农业生产区、人居生活区、生态保育区、人居生活-农业生产复合区、人居生活-生态保育复合区、生态保育-农业生产复合区、农业生产-人居生活-生态保育综合发展区和农业生产-人居生活-生态保育综合协调区8种功能类型区,可为完善长江经济带乡村功能的空间布局提供科学依据。 相似文献
15.
16.
Fully normalized spherical cap harmonics: application to the analysis of sea-level data from TOPEX/POSEIDON and ERS-1 总被引：2，自引：0，他引：2
We introduce two sets of fully normalized harmonics for the spectral analysis of functions defined on a spherical cap. The harmonics are the products of Fourier functions and the fully normalized associated Legendre functions of non-integer degree. Using Sturm-Liouville theory for boundary-value problems, we present two convenient and stable formulae for computing the zeros of the associated Legendre functions that form two sets of orthogonal functions. Formulae for the stable numerical evaluation of the fully normalized associated Legendre functions of non-integer degree that avoid the gamma function are also derived. The result from the expansions of sea-level anomaly from altimetry into Set 2 fully normalized cap harmonics shows fast convergence of the series, and the degree variances decay rapidly without aliasing effects. The zero-degree coefficients (Set 2) of sea-level anomaly from TOPEX/ POSEIDON (T/P) and ERS-1 indicate an El Niño event during 1993 January-1993 July, and a La Niño event during 1993 November-1994 July, although the ERS-1 result is less obvious. Ocean circulations over the South China Sea and the Kuroshio area are clearly identified with the low-degree expansions of sea-surface topography (SST) from T/P and ERS-1. A cold-core eddy of 4° in diameter centred at 17.5°N, 118 E was detected with the expansion of SST from T/P cycle 47, and a property of the cap harmonics is used to compute this eddy's kinetic energy. The kinetic energy is at a low in winter and high in summer, and its variation seems to be periodic with an amplitude of 0.4 m2 S-2 . 相似文献
17.
We present a design for a piston corer that can take a sediment core up to 1 m long, with an undisturbed sediment–water interface.
The coring device possesses a tripod unit and a core-tube unit, the latter comprised of a core tube, a piston with a wire,
a drive weight in which the core tube is mounted and a steel rod. The tripod stands on the sediment surface during coring,
stabilizing the system and serving as an anchor point for the piston wire. A ball clamp, the critical component of the design,
is mounted on top of the tripod. The steel rod runs through the ball clamp and at its lower end, holds the drive weight and
the core tube. The ball clamp allows the core tube to slide downward, while the piston is held in a fixed vertical position
by the wire connected to the tripod. When the corer is lifted, however, the ball clamp locks. This makes it possible to operate
the corer with a single cable, because the piston is not subject to any lifting force when the corer is retrieved. The piston
remains in position in the core tube even if the collected sediment core is very short. The piston corer can be deployed from
a raft or a boat. 相似文献
18.
本文研究了1971—2015年世界铁矿石供需与流动格局的时空变化,结果显示：① 世界铁矿石年产量期末比期初增加了12.26亿t,年均增长2.17%;1992年以前,欧洲曾是世界铁矿石的消费重心,但随后亚洲后来居上。② 研究期内世界铁矿石输出量年均增长达3.7%,大洋洲和南美洲成为铁矿石的主要输出地,2015年占世界的比重分别达53.73%和26.23%;本世纪以来铁矿石输入量最大的是中国、日本和韩国,2015年分别占世界总量的65.07%、8.94%和5%。③ 基于“场”理论,采用位势、“源”、“汇”、迹线等概念审视全球铁矿石流场的基本特征和流场成因,发现世界铁矿石流动的“位势”北半球较低,而南半球较高;亚洲、欧洲是主要的汇流场,大洋洲、南美洲是主要的源流场。本文研究揭示了近半个世纪以来世界铁矿石资源的流动状态及其演变过程,对于我国科学地制定产业政策具有重要价值。 相似文献
19.
S. Giralt M. T. Rico-Herrero J. C. Vega B. L. Valero-Garcés 《Journal of Paleolimnology》2011,46(3):487-502
Monthly limnological monitoring in Lake Sanabria (Spain) since 1986 provided a unique opportunity to test relationships among
climate, hydrology and lake dynamics and how they are recorded in the lake sediments. Four datasets were employed: (1) meteorological
(monthly maximum and minimum air temperature and total precipitation), (2) limnological (Secchi disk, water temperature, conductivity,
pH, dissolved oxygen, nitrate, silicon, total and reactive phosphorus, and total chlorophylls and chlorophyll a), (3) hydrological (Tera River water input and output), and (4) XRF core scanner measurements carried out in short cores.
Linear models between the different dataset variables allowed us to characterize the climate signal transmission from one
to the other and cross-correlation analyses permitted us to identify the different response times (if any) between them. Principal
Component Analyses (PCA) of the limnological and geochemical datasets allowed us to identify the main processes that link
lake dynamics, primarily nutrient supply and organic productivity, with some sedimentological processes, e.g. organic matter
and phosphorus accumulation. Sediment chronology was established by gamma spectrometry (210Pb). Water input to Lake Sanabria is controlled mostly by the Tera River input and is linked directly to precipitation. Response
of the Lake Sanabria water budget to climate oscillations is immediate, as the strongest correlation between these two datasets
occurs with no lag time. PCA of the limnological dataset indicated that most of the variance is related to nutrient input,
and comparison with the Tera River water discharge shows that nutrient input was controlled mainly by oscillations in the
hydrological balance. The lag time between the hydrological and limnological datasets is 1 month. The PCA of the XRF core
scanner dataset showed that the principal process that controls the chemical composition of the Lake Sanabria sediments is
related to sediment and nutrient delivery from the Tera River and organic productivity. Comparison of the nutrient input reconstructed
using the limnological dataset and the XRF core scanner data indicated that the sediments act as a low-pass filter, smoothing
the climate signal. It was, however, possible to establish the link between these datasets, and obtain a quantitative reconstruction
of precipitation for the 1959–2005 AD period that captures the regional variability. This quantitative precipitation reconstruction
suggests it is possible to obtain accurate climate reconstructions using non-laminated sediments. 相似文献
20.
中部六省先进装备制造业人才开发合作,既是中部六省先进装备制造业振兴的核心推动力,同时也是实现中部崛起、推进中部地区经济社会一体化进程的重要组成部分和核心推动力.为了推进中部六省先进装备制造业人才开发合作,需要转变政府部门职能、推动企业的人才开发;打破地域行政壁垒、建立人才开发合作的共同市场;加强人才开发合作协调机制、拓展人才合作领域;搞好人才服务体系建设,优化人才开发合作环境. 相似文献