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   

土地征用制度改革的探索   总被引：1，自引：0，他引：1       下载免费PDF全文

秦泗彦  田宏红  张传亮 《山东国土资源》2003,19(6):29-31,41

征地补偿安置是当前群众反映最强烈并迫切要求解决的问题。要解决该问题必须进行土地征用制度改革．由政府按照市场公平原则向农民集体征购土地，实行统一的土地征购制度。  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   

利用高光谱数据进行植被生化成分反演方法研究   总被引：3，自引：0，他引：3  

张凤丽  万余庆 《地球信息科学学报》2001,3(4):71-75

高光谱数据包含着丰富光谱信息,能够定量地分析物质成分^[1]。由高光谱数据,可以运用多元逐步线性回归方法反演植被生化组分含量,从而达到监测植被生长状况的目的^[2]。本文具体介绍了多元逐步线性回归方法,及其在氮、木质素和纤维素含量估算中的应用。  相似文献   

关于建设菏泽数字国土工程的初步探讨          下载免费PDF全文

张九献  徐晓林 《山东国土资源》2004,20(4):60-63

菏泽数字国土工程主要包括国土资源政务管理信息、土地管理信息、地质矿产资源信息、国土测绘管理信息和国土资源法规监察信息。3S术是其工程中空间数据获取和管理的技术基础。在工程建设中应首先科学编制建设规划。通过规划确定方针，提出目标，明确任务，有序地开展建设。  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