Luminescence dating of sand–loess sequences and response of Mu Us and Otindag sand fields (north China) to climatic changes     

Yali Zhou  Huayu Lu  Jiafu Zhang  Joseph A. Mason  Liping Zhou 《第四纪科学杂志》2009,24(4):336-344

The sand–loess transition zone in north China is sensitive to climate change, and is an ideal place to investigate past environmental changes. However, past climate change at millennial–centennial timescales in this region has not been well reconstructed because of limited numerical dating. Alternations of sandy loam soils with aeolian sand layers in the Mu Us and Otindag sand fields, which lie along the sand–loess transition zone, indicate multiple intervals of dune activity and stability. This change is probably a response to variations of the East Asian monsoon climate during the late Quaternary. The single aliquot regeneration (SAR) optically stimulated luminescence (OSL) dating protocol, which has been successfully applied to aeolian deposits worldwide, is applied to these two sand fields in this study. The OSL ages provide reliable constraints for reconstruction of past climate changes at suborbital timescale. Sections in both sand fields contain aeolian sand beds recording millennial‐scale episodes of dry climate and widespread dune activation, including episodes at about the same time as Heinrich Event 5 and the Younger Dryas in the North Atlantic region. These results demonstrate the potential of aeolian sediments in semi‐arid north China to record millennial‐scale climatic events, and also suggest that dry–wet climate variation at the desert margin in China may be linked to climatic change elsewhere in the Northern Hemisphere, through atmospheric circulation. This article was published online on 27 November 2008. An error was subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected (16 December 2008). Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Disc–Planet Interactions: Migration and Resonances in Extrasolar Planetary Systems     

J. C. B. Papaloizou 《Celestial Mechanics and Dynamical Astronomy》2003,87(1-2):53-83

We consider orbital resonances in multiplanet systems. These are expected to arise during or just after formation in a gaseous disc. Disc–planet interaction naturally produces orbital migration and circularization through the action of tidal torques which in turn may lead to an orbital resonance. The mass and angular momentum content of the disc is likely to be comparable to that in the planets so that it is essential to fully incorporate the disc in the analysis.We study the orbital evolution of two planets locked in 2:1 commensurability through migration tidally induced by the disc using both analytic methods and numerical hydrodynamic simulations. The planets are assumed to orbit in an inner cavity containing at most only a small amount of disc material. Results are found to be sensitive to initial surface density profile, planet masses and disc parameters. The evolution may range between attaining and subsequently maintaining a resonance lock with two angles librating to divergent migration with no commensurability formed. In the former case eccentricities increase monotonically with time while the system undergoes inward migration. If the migration is halted by loss of the disc leaving the planets in a final configuration, there is likely to be a low probability of seeing resonant planets at small radii as well as a sensitive dependence on past history.We have also considered a multiplanet system in secular apsidal resonance. We consider the system as being in just one secular normal mode and include the effects of a gaseous disc. It is suggested that a normal mode may be selected by adding in some weak dissipative process in the disc and that it may remain, involving only the planets, when the disc is slowly removed.  相似文献   

智能照明系统在现代建筑照明中的应用研究   总被引：1，自引：0，他引：1  

陈丹 《成都信息工程学院学报》2007,22(6):735-738

在对传统照明系统和智能照明系统进行对比分析的基础上,剖析了智能照明系统的控制策略,并结合实际的工程应用,着重讨论了基于ABB I-Bus产品的智能照明控制系统的实现,结果表明该系统具有高效、便捷、节约能源等优点.同时,还对系统与建筑物楼宇自控系统问的系统集成方式进行了研究.  相似文献   

Interpolating paleovegetation data with an artificial neural network approach     

Bjrn Grieger 《Global and Planetary Change》2002,34(3-4)

To drive an atmospheric general circulation model (AGCM), land surface boundary conditions like albedo and morphological roughness, which depend on the vegetation type present, have to be prescribed. For the late Quaternary there are some data available, but they are still sparse. Here an artificial neural network approach to assimilate these paleovegetation data is investigated. In contrast to a biome model the relation between climatological parameters and vegetation type is not based on biological knowledge but estimated from the available vegetation data and the AGCM climatology at the corresponding locations. For a test application, a data set for the modern vegetation reduced to the amount of data available for the Holocene climate optimum (about 6000 years B.P.) is used. From this, the neural network is able to reconstruct the complete global vegetation with a kappa value of 0.56. The most pronounced errors occur in Australia and South America in areas corresponding to large data gaps.  相似文献   

地理信息系统数据库设计     

潘珩 《成都信息工程学院学报》2006,21(4):555-558

首先分析了地理信息系统的组成、地理信息系统数据的特征、地理信息系统数据库的功能，然后进行了中心式导航系统数据库的设计，给出了数据库模型的E-R图，最后描述了空间地理信息的查询功能。  相似文献   

使用模块方式进入系统空间     

薛筱宇  张钟澍  徐虹 《成都信息工程学院学报》2003,18(2):115-118

LINUX，一个优秀的代码开放的操作系统。对其内核代码的分析，无论对编程或者学习操作系统原理都将事半功倍。然而处于安全性考虑，CPU的设计者将系统空间和用户空间分离，这个措施造成了对内核代码进行调试运行的困难。有许多方法可以使用户程序进入系统空间，比如中断方式、系统调用方式……我们介绍的是采用模块的方式使应用程序进入系统空间。  相似文献   

Preliminary Study on the Translunar Halo Orbits of the Real Earth–Moon System     

Miquel A. Andreu 《Celestial Mechanics and Dynamical Astronomy》2003,86(2):107-130

The computation of translunar Halo orbits of the real Earth–Moon system (REMS) has been an open problem for a long time, but now, it is possible to compute Halo orbits of the REMS in a systematic way. In this paper, we describe the method used for the numerical computation of Halo orbits for a time span longer than 41 years. Halo orbits of the REMS are computed from quasi-periodic Halo orbits of the quasi-bicircular problem (QBCP). The QBCP is a model for the dynamics of a spacecraft in the Earth–Moon–Sun system. It is a Hamiltonian system with three degrees of freedom and depending periodically on time. In this model, Earth, Moon and Sun are moving in a self-consistent motion close to bicircular. The computed Halo orbits of the REMS are compared with the family of Halo orbits of the QBCP. The results show that the QBCP is a good model to understand the main features of the Halo family of the REMS.  相似文献   

银河系运动学参数的确定     

俎中良  赵君亮 《中国科学院上海天文台年刊》2004,(1)

利用 2 0 2个太阳附近疏散星团的视向速度和自行观测资料 ,对太阳的运动和银河系的运动学参数进行了研究。其中 ,距离在 0 .5kpc到 2kpc之间的 12 8个疏散星团对平均太阳运动分量的解算结果是 (u0 ,v0 ,w0 ) =(- 13.8± 1.4 ,- 5 .0± 1.6 ,- 11.6± 2 .9)km/s ;Oort常数和银河系径向运动参数的解算结果分别为 (A ,B) =(16 .9± 1.1,- 11.6± 2 .6 )km·s- 1·kpc- 1及 (C ,D) =(2 .5± 1.1,- 2 .1± 0 .9)km·s- 1·kpc- 1。  相似文献   

REVIEWS OF GEOGRAPHIC SOFTWARE     

《The Professional geographer》1987,39(1):85-94

Reviews of geographic software in this article: DEMO-GRAPHICS: WORLD POPULATIONS AND PROJECTIONS. ESP GAUSS. CEMODEL S. Damus LIMDEP. William H. Greene MICROSTAT 4.1 OTIS PCIPS. (Personal Computer Image Processing System) . H.J. Meyers and R. Bernstein. REGRESSION ANALYSIS OF TIME SERIES (RATS) SPSS/PC+ URBAN DATA MANAGEMENT SOFTWARE (UDMS)  相似文献   

安塞县退耕还林工程与农业生态经济社会系统协同效应的分析——基于VAR模型的实证分析     

李玥  王继军  胡小宁  赵晓翠 《资源与生态学报(英文版)》2021,12(2):292-301

针对黄土丘陵区退耕还林工程与农业生态经济社会系统协同性研究滞后的现实,运用向量自回归模型(VAR),通过对安塞县1995–2014年相关数据的分析,明确了其协同效应。退耕还林工程结果表明:退耕还林工程对农业生态经济社会系统产生作用的同时,农业生态经济社会系统的改变也反作用于退耕还林工程,明确了退耕还林工程与农业生态经济社会系统之间存在协同互馈的效应。在这一协同过程中,退耕还林工程对农业生态系统的贡献率达34%,明显高于退耕对农业经济系统、农业社会系统的贡献率;农业经济系统对退耕还林工程的影响程度最为明显,贡献率最高点达55.3%且常年稳定,这些都与现实状况相一致。基于此,为了推进退耕还林工程与农业生态经济社会系统的优化耦合,需要在增强生态功能基础上,通过发展碳汇产业促使生态功能的经济显化,构建以提高区域内资源的有效利用率为核心的农业产业–资源链。  相似文献