500 m口径球面大射电望远镜台址BP神经网络优选     

刘宏  宋建波  王文俊  彭勃  南仁东 《地质科技情报》2006,25(1):104-108

从贵州众多的喀斯特洼地中优选出适宜的大射电望远镜候选台址是一个复杂的系统分析过程,需综合考虑洼地几何条件、工程条件、地质条件、气象条件和无线电波环境等因素.由于各因素具有复杂性、模糊性和难以量化等特点,因此在洼地评价和台址优选中采用最能有效反映各评价指标复杂关系的多层人工神经网络BP模型,并以最小挖填方率来量化洼地拟合望远镜球冠时土石方工程量、以洼地最适宜口径来量化大射电望远镜口径规模.优选结果表明,在集中分布于黔南和黔西南的82个喀斯特洼地中,评价等级为"较好"的有30个,"好"的有6个.优选出的36个洼地均具备作为望远镜候选台址的条件,且集中分布于以下三大区域内:①以平塘、紫云、惠水、罗甸、荔波为中心的区域;②以普定、安顺、镇宁为中心的区域;③以安龙、兴义和关岭为中心的区域.  相似文献   

滑波治理措施的特性与优化设计探讨     

孔祥国 《岩土工程技术》2006,20(6):287-289,323

通过对滑坡治理工程中各种措施的特性分析,阐明了它们适用的地质条件和地质环境,结合工程实例探讨了滑坡治理优化设计的要点,提出了滑坡治理工程的优化设计思路。  相似文献   

Thermosteric Effects on Interannual and Long-term Global Mean Sea Level Changes     

J. L. Chen  C. R. Wilson  B. D. Tapley  X. G. Hu 《Journal of Geodesy》2006,80(5):240-247

We investigate global mean sea level (MSL) changes and different geophysical contributions at interannual and long-term (decadal) time-scales. Thermosteric effects of global MSL changes are estimated from ocean temperature anomaly data for the period 1955–2003 from the World Ocean Database 2001 (WOD01), plus additional data processed through June 2004. Estimates based on WOD01 show significant differences to previously published results based on similar temperature anomaly data from the World Ocean Database 1998 (WOD98), especially during the period overlapping with the TOPEX/Poseidon satellite altimeter mission. During this period (1993–2004), the WOD01-estimated thermosteric contribution of global MSL change is less than half of the estimate from WOD98 (1.3 ± 0.1 vs. 3.0 ± 0.6 mm/year), as compared to the rate of 2.6 ± 0.06 mm/year observed by satellite altimeters. The larger uncertainty in ocean temperature profiles and incomplete data collection in WOD98, especially in the later years (1997 and 1998) appear to be the major error sources to the overestimated steric effects by WOD98. During the entire 50-year period, the steric effect on global MSL change amounts to about 0.34–0.39 (±0.05) mm/year. Strong interannual and decadal variability exists in estimated thermosteric contributions to the global MSL change, and (surprisingly) the thermosteric effect does not show any pronounced contribution to the strong interannual variability during the 1997/1998 El Niño/La Niña event. Our analysis based on the National Centers for Environmental Prediction reanalysis atmospheric model and the National Oceanic and Atmospheric Administration Climate Prediction Center global land data assimilation system indicates that atmospheric water vapor and terrestrial water storage changes show strong interannual variability that is well correlated with observed global MSL change, and could have significant effects on interannual global MSL changes.  相似文献   

二十世纪九十年代区域气候模拟研究进展   总被引：44，自引：9，他引：35  

赵宗慈  罗勇 《气象学报》1998,56(2):225-241

由于区域气候异常与社会经济及人类发展有紧密联系,因而长期以来受到各国气候学家的极大重视,与此密切相关的对区域气候的模拟研究也有了较大发展。进入２０世纪９０年代以来,区域气候模拟研究的进展更加明显。文中将着重分析全球气候模式对区域气候模拟的可靠性与不确定性;国内外对区域气候的模拟研究进展;以及对区域气候变化模拟研究的展望。  相似文献   

GPS地基遥感大气水汽总量分析   总被引：35，自引：4，他引：31       下载免费PDF全文

李成才  毛节泰 《应用气象学报》1998,9(4):470-477

概述了利用地基GPS接收机遥感大气水汽总量的一般方案,分析了各种因素导致的误差以及相应的消除或降低办法,总结了由湿项延迟计算水汽总量的方法。介绍了GPS/STORM试验和两种解算方案。最后提出试验研究方案和在我国进行业务应用要解决的问题。  相似文献   

Global Oceanic Climate Anomalies in 1980''''s     

符淙斌  谢力 《大气科学进展》1998,(2)

ＧｌｏｂａｌＯｃｅａｎｉｃＣｌｉｍａｔｅＡｎｏｍａｌｉｅｓｉｎ１９８０′ｓＦｕＣｏｎｇｂｉｎ（符淙斌）ａｎｄＸｉｅＬｉ（谢力）ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉｃＰｈｙｓｉｃｓ,ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓ,Ｂｅｉｊｉｎｇ...  相似文献   

Estimation of dynamic ocean topography in the Gulf Stream area using the Hotine formula and altimetry data   总被引：3，自引：2，他引：1  

Changyou Zhang 《Journal of Geodesy》1998,72(9):499-510

Two modifications of the Hotine formula using the truncation theory and marine gravity disturbances with altimetry data are developed and used to compute a marine gravimetric geoid in the Gulf Stream area. The purpose of the geoid computation from marine gravity information is to derive the absolute dynamic ocean topography based on the best estimate of the mean surface height from recent altimetry missions such as Geosat, ERS-1, and Topex. This paper also tries to overcome difficulties of using Fast Fourier Transformation (FFT) techniques to the geoid computation when the Hotine kernel is modified according to the truncation theory. The derived absolute dynamic ocean topography is compared with that from global circulation models such as POCM4B and POP96. The RMS difference between altimetry-derived and global circulation model dynamic ocean topography is at the level of 25cm. The corresponding mean difference for POCM4B and POP96 is only a few centimeters. This study also shows that the POP96 model is in slightly better agreement with the results derived from the Hotine formula and altimetry data than POCM4B in the Gulf Stream area. In addition, Hotine formula with modification (II) gives the better agreement with the results from the two global circulation models than the other techniques discussed in this paper. Received: 10 October 1996 / Accepted: 16 January 1998  相似文献   

1990—1995年全球灾害地震统计特征     

李卫平 《华南地震》1998,18(2):27-36

研究了１９９０－１９９５年间全球大地震活动及重大灾害地震的时空强分布特征,着重讨论了灾害地震与地震活动水平,人文地理,经济地理和发震时间等各种因素的密切关系。  相似文献   

考虑回水顶托影响的水位预报研究   总被引：6，自引：2，他引：4       下载免费PDF全文

芮孝芳  姜广斌 《水科学进展》1998,9(2):124-129

将有回水顶托影响的河段视为多输入-单输出系统,把水位过程视为时间序列,用时间序列分析最优控制理论,建立了可考虑回水顶托影响的水位过程预报模型。提出了在棱柱形河道情况下,以时段水位涨差作变量时,模型中各参数应满足的物理性约束条件;较好地解决了长江荆江河段中受回水顶托影响的石首站的水位过程预报问题,为水位过程预报提供了一条不同于水文学途径和水力学途径的建模途径。  相似文献   

基于遗传算法的优化搜索技术   总被引：1，自引：0，他引：1  

张帆  唐湘蓉 《矿物岩石》1998,(Z1)

遗传算法是借鉴生物界自然选择和自然遗传机制的随机化搜索算法,其主要特点是搜索不依赖于梯度信息,能自动获取和积累有关搜索空间的知识,并自适应地控制搜索过程,从而得到最优解或准最优解的通用搜索算法。它尤其适合于组合优化、机器学习、自适应控制、规划设计和人工智能等领域。  相似文献