膨胀地球基本参数的初值及其平均变化率   总被引：6，自引：0，他引：6       下载免费PDF全文

陈志耕 《地球物理学报》1990,33(5):611-618

本文讨论了地球膨胀过程的初始半径R₀、膨胀起始时间t₀以及半径R、转动惯量I、地表重力加速度g和反映地球内部物质分布状态参数y等膨胀基本参数的平均变化率。研究结果表明,在地球的地质年龄之内,地球膨胀的初始半径R₀>4619km,膨胀的起始时间t₀>43.8×10²Ma,膨胀过程中的地球半径R、物质分布状态参数y、转动惯量I、地表重力加速度g和表面积S随时间的平均变化率分别为:dR/dt=4×10^-4m/a,dy/dt=-6.7×10¹²/a,dI/dt=8.49×10²⁷kg·m~2/a,dg/dt=-1.23×10^-10kg·s^-2/a和ds/dt=6.41×10⁴m²/a。地球膨胀过程中的半径平均增长率,是首次用天文学方法研究得出,且该值介于其他作者用古地磁、古地理等方法所求得的地球半径增长率若干数值之间。  相似文献   

Contraction and convergence of in-use metal stocks to meet climate goals     

《Global Environmental Change》2021

The foundations of modern society are based on metals, yet their production is currently placing considerable strain on the Earth’s carrying capacity. Here, we develop a century-long scenario for six major metals (iron, aluminum, copper, zinc, lead, and nickel) harmonized with climate goals, with the goal of establishing science-based targets. We show that for the metal sector to contribute proportionally to emission reductions targets of the industrial sector, global in-use metal stocks need to converge from the current level of around 4 t/capita to about 7 t/capita. This will require today’s high-income countries to contract their per capita stock from current levels of about 12 t/capita to make room for growth in countries that are presently classified as middle- and low-income countries. In such a contraction and convergence scenario, primary production of all six metals will peak by 2030, and secondary production will surpass primary production by at least 2050. Consequently, cumulative ore requirements over the 21st century will remain below currently identified resources, implying that natural ore extraction will be limited by emissions budgets before existing resources can be depleted. Importantly, realizing such system changes will require urgent and concerted international efforts involving all countries, but specific responsibilities will vary according to income level. Namely, wealthy countries will need to use existing metal stocks more intensively and for longer periods to reduce stock replacement demand, while poor countries will need to develop long-lasting and material-efficient infrastructure to curtail stock expansion demand in the first half of the 21st century.  相似文献   

A new ellipsoidal gravimetric, satellite altimetry and astronomic boundary value problem, a case study: The geoid of Iran     

Abdolreza Safari  Alireza A. Ardalan  Erik W. Grafarend   《Journal of Geodynamics》2005,39(5):545

A new gravimetric, satellite altimetry, astronomical ellipsoidal boundary value problem for geoid computations has been developed and successfully tested. This boundary value problem has been constructed for gravity observables of the type (i) gravity potential, (ii) gravity intensity (i.e. modulus of gravity acceleration), (iii) astronomical longitude, (iv) astronomical latitude and (v) satellite altimetry observations. The ellipsoidal coordinates of the observation points have been considered as known quantities in the set-up of the problem in the light of availability of GPS coordinates. The developed boundary value problem is ellipsoidal by nature and as such takes advantage of high precision GPS observations in the set-up. The algorithmic steps of the solution of the boundary value problem are as follows:

- Application of the ellipsoidal harmonic expansion complete up to degree and order 360 and of the ellipsoidal centrifugal field for the removal of the effect of global gravity and the isostasy field from the gravity intensity and the astronomical observations at the surface of the Earth.

- Application of the ellipsoidal Newton integral on the multi-cylindrical equal-area map projection surface for the removal from the gravity intensity and the astronomical observations at the surface of the Earth the effect of the residual masses at the radius of up to 55 km from the computational point.

- Application of the ellipsoidal harmonic expansion complete up to degree and order 360 and ellipsoidal centrifugal field for the removal from the geoidal undulations derived from satellite altimetry the effect of the global gravity and isostasy on the geoidal undulations.

- Application of the ellipsoidal Newton integral on the multi-cylindrical equal-area map projection surface for the removal from the geoidal undulations derived from satellite altimetry the effect of the water masses outside the reference ellipsoid within a radius of 55 km around the computational point.

- Least squares solution of the observation equations of the incremental quantities derived from aforementioned steps in order to obtain the incremental gravity potential at the surface of the reference ellipsoid.

- The removed effects at the application points are restored on the surface of reference ellipsoid.

- Application of the ellipsoidal Bruns’ formula for converting the potential values on the surface of the reference ellipsoid into the geoidal heights with respect to the reference ellipsoid.

- Computation of the geoid of Iran has successfully tested this new methodology.

盐湖地学的研究进展和发展方向   总被引：11，自引：0，他引：11  

胡东生 《地球科学进展》1997,12(5):411-415

在确定盐湖科学的专业范围并划分分支学科的基础上，对盐湖地学研究中的几个重大理论问题进行了讨论：１．大陆盐湖盆地成盐环境演化过程；２．盐湖卤水的天然随机连续煊化；３．盐湖沉积物质流和湖泊演变旋回发展事件；４．盐湖演变与全球变化。  相似文献   

Circumstellar molecular line absorption and emission in the optical spectra of post-AGB stars     

Eric J. Bakker  Henny J. G. L. M. Lamers  L. B. F. M. Waters  Ton Schoenmaker 《Astrophysics and Space Science》1995,231(1-2):335-338

We present preliminary results obtained with the European Observation Network. This network consists of 9 observatories in the Czech Republic, Germany and Bulgaria and has been involved in the BACODINE activities since April 1, 1994. We also discuss related problems such as the background of unknown variable stars and suggest a strategy for work in this area.  相似文献   

Water, Salt, Phosphorus and Nitrogen Budgets of the Japan Sea   总被引：1，自引：0，他引：1  

Tetsuo Yanagi 《Journal of Oceanography》2002,58(6):797-804

Water, salt, phosphorus and nitrogen budgets of the Japan Sea have been calculated by box model analysis using historical data. Average residence time of the Tsushima Warm Current Water in the upper 200 m is 2.1 years and that of the Japan Sea Proper Water is 90 years. The salt flux from the Tsushima Strait balances those through the Tsugaru and Soya Straits. Average residence times of phosphorus and nitrogen from the Tsushima Strait are 2.2 years and 1.6 years, respectively, in the upper 200 m of the Japan Sea. Total nitrogen/total phosphorus ratios of riverine load, the Tsushima Warm Current water and the water in the Japan Sea are 16.4, 16.6 and 11.3, respectively. This suggests that denitrification is dominant in the Japan Sea. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Numerical investigation of pile installation effects in sand using material point method     

《Computers and Geotechnics》2016

The installation of displacement piles in sand leads to severe changes in the stress state, density and soil properties around the pile tip and shaft, and therefore has a significant influence on the pile bearing capacity. Most current numerical methods predicting pile capacity do not take installation effects into account, as large deformations can lead to mesh distortion and non-converging solutions. In this study, the material point method (MPM) is applied to simulate the pile installation process and subsequent static pile loading tests. MPM is an extension of the finite element method (FEM), which is capable of modelling large deformations and soil-structure interactions. This study utilizes the moving mesh algorithm where a redefined computational mesh is applied in the convective phase. This allows a fine mesh to be maintained around the pile tip during the installation process and improves the accuracy of the numerical scheme, especially for contact formulation. For the analyses a hypoplastic constitutive model for sand is used, which takes into account density and stress dependent behaviour. The model performs well in situations with significant stress level changes because it accounts for very high stresses at the pile tip. Numerical results agree with centrifuge experiments at a gravitational level of 40 g. This analysis confirms the importance of pile installation effects in numerical simulations, as well as the proposed numerical approach’s ability to simulate installation and static load tests of jacked displacement piles.  相似文献   

山东胶莱盆地下白垩统莱阳组物质组分特征及其对源区的制约   总被引：4，自引：1，他引：3  

李双应  孟庆任  李任伟  王道轩  储书武 《岩石学报》2008,24(10):2395-2406

位于中国东部苏鲁造山带北侧的胶莱盆地发育早白垩世莱阳组,厚约2000m,为一套陆相碎屑沉积,包括砾岩、砂岩和页岩,以及少量泥灰岩、白云岩和凝灰岩。它可以分为4个岩性段,每个段大致形成一个向上变细的旋回。砾岩砾石成分主要为花岗片麻岩、黑云斜长片麻岩、混合花岗岩和大理岩,其次是黑云片岩、灰岩和沉积碎屑岩、火山岩和花岗岩等。莱阳组砂岩主要由岩屑长石砂岩以及岩屑砂岩组成,具有低的成分成熟度,Q／（F＋L）平均为0．42（0．19～0．84）。石英主要由单晶石英组成,长石包括斜长石、微斜长石等,岩屑主要为火山岩和变质岩,其次为沉积岩。6个砂岩地球化学样品分析表明,砂岩的SiO2、Al2O3、TiO2、Fe2O3^T;、MnO、MgO、CaO、Na2O、K2O的平均含量分别为70．53％、13．10％、0．41％、3．09％、0．06％、1．23％、1．69％、3．38％和3．38％,类似于晚元古代造山带砂岩成分。莱阳组砂岩稀土元素分析表明,La含量为38．4×10^-6（28．0×10^-6-50．5×10^-6）,Ce含量为69．3×10^-6（58．1×10^-6～81．3×10^-6）,稀土总量为134×10^-6～197×10^-6,轻稀土明显富集,La/Yb为20．18（11．91～25．98）,（La／Yb）。为13．60（8．03～17．52）,有中等到弱的Eu负异常（δEu=0．58-0．88）,Ce为弱的负异常（δCe=0．78～0．97）。Ce含量、稀土总量和Eu异常揭示源区岩石形成时的构造背景主要为大陆岛弧。砾石统计揭示,莱阳组物源区的剥蚀序列按时间顺序应该是花岗片麻岩、黑云斜长片麻岩-大理岩-脉石英、灰岩和碎屑岩-正长岩。砂岩点统计、F1-F2判别图、La—Th-Sc和Th—Sc—Zr／10判别图揭示,莱阳组砂岩主要源区属于大陆弧的长英质火成岩区,少许来自再循环造山带。砂岩Zr／Y比值揭示莱阳组砂岩与分布在山东荣成地区具有大陆弧构造背景的片麻岩具有亲缘性。这表明山东胶菜盆地莱阳组砂岩源区主要来自苏鲁造山带,其次有少许来自扬子陆块。造山带周缘盆地的陆源沉积物中,砂岩的碎屑组分以及地球化学特征具有源区构造背景的继承性,反映的是源岩形成的构造环境。  相似文献   

Astronomical-topographic levelling using high-precision astrogeodetic vertical deflections and digital terrain model data   总被引：2，自引：1，他引：1  

Christian Hirt  Jakob Flury 《Journal of Geodesy》2008,82(4-5):231-248

At the beginning of the twenty-first century, a technological change took place in geodetic astronomy by the development of Digital Zenith Camera Systems (DZCS). Such instruments provide vertical deflection data at an angular accuracy level of 0.̋1 and better. Recently, DZCS have been employed for the collection of dense sets of astrogeodetic vertical deflection data in several test areas in Germany with high-resolution digital terrain model (DTM) data (10–50 m resolution) available. These considerable advancements motivate a new analysis of the method of astronomical-topographic levelling, which uses DTM data for the interpolation between the astrogeodetic stations. We present and analyse a least-squares collocation technique that uses DTM data for the accurate interpolation of vertical deflection data. The combination of both data sets allows a precise determination of the gravity field along profiles, even in regions with a rugged topography. The accuracy of the method is studied with particular attention on the density of astrogeodetic stations. The error propagation rule of astronomical levelling is empirically derived. It accounts for the signal omission that increases with the station spacing. In a test area located in the German Alps, the method was successfully applied to the determination of a quasigeoid profile of 23 km length. For a station spacing from a few 100 m to about 2 km, the accuracy of the quasigeoid was found to be about 1–2 mm, which corresponds to a relative accuracy of about 0.05−0.1 ppm. Application examples are given, such as the local and regional validation of gravity field models computed from gravimetric data and the economic gravity field determination in geodetically less covered regions.  相似文献   

考虑坝体材料非线性的混凝土拱坝地震反应分析     

赵密  杜修力  廖维张  唐庆 《震灾防御技术》2008,3(1):79-84

本文基于可信概率水准的破坏性强震作用,针对小湾高拱坝进行了考虑坝体材料非线性的拱坝地震反应分析。在分析模型中,同时考虑了无约束域地震能量辐射效应和近域地基材料非均匀性的影响。为了实现非线性条件下的静、动力组合分析,利用显式有限元结合修正的黏弹性人工边界的开放系统时域静、动力统一分析方法进行了求解,对在自重作用下的初始静力解计算采用了动力松弛技术。  相似文献