3-D Spatial Variation of b-Values of Magnitude-Frequency Distribution Beneath the Kanto District, Japan     

Yosihiko Ogata  Masajiro Imoto  Koichi Katsura 《Geophysical Journal International》1991,104(1):135-146

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科技兴农在宁南     

杨永良 《山地学报》1990,(4)

宁南县重视农业技术的推广,促进了农业生产的发展,农业总产值1989年达5208万元,比1976年增长1.2倍。这表明依靠科技进步,振兴山区农业,是发展经济的必由之路。本县将采取有力措施,大搞科技兴农,争取更上一层楼。  相似文献   

Pollen‐inferred palaeoclimate reconstructions in mountain areas: problems and perspectives     

Elena Ortu  Simon Brewer  Odile Peyron 《第四纪科学杂志》2006,21(6):615-627

Transfer functions are an efficient tool for the quantitative reconstruction of past climate from low to mid‐elevation pollen sites. However, the application of existing methods to high‐altitude pollen assemblages frequently leads to unrealistic results. In the aim of understanding the causes of these biases, the standard ‘best modern analogue’ method has been applied to two high‐altitude pollen sequences to provide quantitative climate estimates for the Lateglacial and Holocene periods. Both pollen sequences (Laghi dell'Orgials, 2130 m, SW aspect and Lago delle Fate, 2240 m, E aspect) are located in the subalpine belt, on opposing sides of the St. Anna di Vinadio Valley (Italian Maritime Alps). Different results were obtained from the two sequences. The largest differences occurred in palaeotemperature reconstruction, with notable differences in both the values and trends at each site. These biases may be attributed to: (1) a lack of high elevation ‘best modern analogues’ in the database of modern samples; (2) the problem of pollen taxa that have multiple climatic significance; (3) problems related to the complexity of mountainous ecosystems, such as the phenomenon of uphill transport of tree pollen by wind. Possible improvements to the reconstruction process are discussed. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

求解多目标非线性优选问题的算法     

陶华学 《大地测量与地球动力学》2001,21(1):42-45

研究变形监测网布网方案的优化 ,探讨目标权重未知情况下的非线性多目标优化问题 ,给出了一个求解权重未知的多目标非线性优选问题的算法。该算法采用一种新的最小加权偏差优选方法 ,可优选最佳布网方案  相似文献   

Scope of high-frequency time keeping in searches for short-period gamma-ray sources     

M. L. Sapru  A. K. Tickoo  I. K. Kaul  S. K. Kaul  C. L. Bhat  R. K. Kaul  H. S. Rawat  V. K. Senecha  R. C. Rannot  H. Razdan 《Journal of Astrophysics and Astronomy》1990,11(2):141-150

This paper presents a novel technique to derive the absolute time of occurrence of an event with an accuracy of < 200 μs by adapting the HF time synchronization technique to correct for the aging rate and the frequency drift of a temperature-controlled quartz frequency standard. The propagation delay suffered by the HF time signals has been estimated by monitoring the clock error with respect to time signals from five broadcast stations located at distances in the range 500–3700 km from Gulmarg. Using simulated data, we further show the viability of this technique in permitting periodicity searches on timescales of ≥5 milliseconds in cosmic gamma-ray data An erratum to this article is available at .  相似文献   

试述实现创新型国家目标中高校教育的任务     

阚孔璧 《成都信息工程学院学报》2006,21(6):932-934

党和国家提出15年实现创新型国家目标，意义重大，反响强烈。作为高校教育，肩负时代重任。这里就此试述一二，以应广大读者。  相似文献   

The optical reflector system for the CANGAROO-II imaging atmospheric Cherenkov telescope     

A. Kawachi  Y. Hayami  J. Jimbo  S. Kamei  T. Kifune  H. Kubo  J. Kushida  S. LeBohec  K. Miyawaki  M. Mori  K. Nishijima  J. R. Patterson  R. Suzuki  T. Tanimori  S. Yanagita  T. Yoshikoshi  A. Yuki 《Astroparticle Physics》2001,14(4):1492-269

A new imaging atmospheric Cherenkov telescope with a light-weight reflector has been constructed. Light, robust, and durable mirror facets of containing carbon fiber reinforced plastic laminates were developed for the telescope. The reflector has a parabolic shape (f/1.1) with a 30 m² surface area, which consists of 60 spherical mirror facets. The image size of each mirror facet is 0°.08 (FWHM) on average. The attitude of each facet can be adjusted by stepping motors. After the first in situ adjustment, a point image of about 0°.14 (FWHM) over 3° field of view was obtained. The effect of gravitational load on the optical system was confirmed to be negligible at the focal plane. The telescope has been in operation with an energy threshold for γ-rays of 300 GeV since May 1999.  相似文献   

我国省市级大地水准面精化的现状及技术模式   总被引：46，自引：5，他引：41  

宁津生  罗志才  李建成 《大地测量与地球动力学》2004,24(1):4-8

高精度局部大地水准面将为测绘学、地球物理、地球动力学及海洋学等相关学科的发展和应用提供重要的基础地球空间信息。GPS技术结合高精度大地水准面模型可应用于取代传统的高程测量(如三角高程测量和低等级水准测量)，这是当前精化我国省市级大地水准面在测绘领域的主要目的之一。在总结和分析我国目前省市级大地水准面精化的现状、技术模式及特点的基础上，提出了今后精化我国省市级大地水准面的若干建议。  相似文献   

上海天文台MK5A终端系统的安装与测试     

薛祝和  王玲玲  王锦清  涂瑞铭 《天文学进展》2004,22(4):344-349

简要阐述了上海天文台VLBI终端系统的发展历史与性能；介绍了在没有MK4解码器、互联网又不能满足需要的特殊情况下，利用数据质量分析仪(DQA)完成MK5A终端系统安装与测试的过程和方法。目前，MK5A终端系统已经成功地应用于上海天文台所有的VLBI实验。  相似文献   

高精度时间间隔测量技术与方法   总被引：31，自引：0，他引：31  

张延  黄佩诚 《天文学进展》2006,24(1):1-15

时间间隔测量技术,尤其是高精度的时间间隔测量技术意义重大。不论是电信通讯、芯片设计等工程实践,还是原子物理、天文观测实验等理论研究,以及激光测距、卫星定位等航天军事技术,都离不开高精度的时间间隔测量技术。经过几十年的研究,目前已经有多种测量方法。在阐明插值原理之后,依次介绍了直接计数法、扩展法、时间幅度转换法、游标法、抽头延迟线法和差分延迟线法等主要方法。然后对影响测量的几个因素,包括非线性和不定态作了讨论。针对这些不良影响,还探讨了一些提高精度和稳定度的方法,比如非线性校正、PLL(Phase Lock Loop)和DLL (Delay Lock Loop)技术。最后,对时间间隔测量技术的前景作了展望。  相似文献