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71.
峨眉山玄武岩的铂族元素地球化学特征 总被引:38,自引:4,他引:34
采用镍锍试金预处理中子活化分析方法,系统地测定了峨眉山玄武岩的铂族元素含量。14个样品的平均值为:Os=0.39ng/g,Ir=0.0698ng/g,Ru=0.49ng/g,Rh=0.25ng/g,Pt=7.71ng/g,Pd=5.48ng/g。相对于原始上地幔,峨眉山玄武岩的铂族元素分异明显,Os、Ir、Ru、Rh亏损,Pt、Pd富集。(Pt+Pd)/(Os+Ir+Ru)比值(平均13.96)和Pd/Ir比值(平均78.5)显著高于原始上地幔、地幔捕虏体、阿尔卑斯型橄榄岩及科马提岩。铂族元素配分模式为铂钯富集型。以上这些特征表明其原始岩浆为上地幔低程度部分熔融形成的玄武岩浆。 相似文献
72.
多途径解决我国钾盐资源紧缺的对策探讨 总被引:6,自引:0,他引:6
探讨了钾盐矿产的应用,钾盐矿产在世界及我国的分布状况,提出了解决我国钾盐矿产资源紧缺问题的途径。 相似文献
73.
Structure,diversity and stability of two oligochaete communities according to sedimentary inputs in Lake Geneva (Switzerland) 总被引:3,自引:1,他引:3
Two oligochaete communities were sampled monthly during one year in two 35 m deep locations of Lake Geneva (Switzerland).
Organic sedimentation was lower and less variable in station 1 than in station 2 (157 versus 214 g C m−2yr−1). The oligochaete community in station 1 was more diverse and more stable (persistent over time) than in station 2, as long
as the organic sedimentation was low. Diversity and stability decreased in station 1 when the organic sedimentation increased,
and during anOscillatoria bloom. The less diverse community in station 2 was more resistent to these changes. Diversity was associated with environmental
stability, but resistance to perturbation was greater in the simpler community which is adapted to changing environmental
conditions. The value of oligochaete communities as an indicator of the level of eutrophication was reassessed according to
our present data. Changes in the structure of oligochaete communities were related to changes in sedimentation processes. 相似文献
74.
Ho Chi Minh city is a primate city in which wartime dislocations have resulted in severely overcrowded conditions as well as a shrunken economic base. The new government has opted for a policy based on the rapid decanting of a large proportion of the urban population by encouraging internal migration to New Economic Zones in the hinterlands. This policy is based on a hierarchial administrative structure with agricultural productivity as its prime goal. A Green Belt policy has been articulated that uses the New Economic Zones as building blocks. The Green Belts constrain urban growth as well as provide foodstuff for the remaining urban residents. The ultimate objective of the overall policy is a balanced urban and regional environment that is in tune with Vietnam's agricultural economy. 相似文献
75.
河西走廊东部甜菜含糖量预测模式 总被引:1,自引:0,他引:1
运用灰色系统理论中的关联度方法,分析影响武威黄羊镇糖厂含糖量的气象因素,并建立了不含导数项的线性静态模式。经残差修正后,预测精度达98.11%。 相似文献
76.
Dr Claude Lang 《Aquatic Sciences - Research Across Boundaries》1974,36(2):301-350
In Lake Geneva (Switzerland), the macrofauna of the stony lake bottom was studied in seven stations from 1969 to 1971. The
modifications in animal communities since the beginning of the century can be attributed partly to the increasing eutrophication
of the lake and partly to the introduction of new species. The stations are classified according to the structure of their
animal communities, which enables us to deduce the degree of eutrophication of each station. The analysis of factors which
influence the animals' microdistribution on lakebottom stones reveals many complicated interactions. As a result of this complexity,
further research projects were concentrated on leeches (Hirudinea) which colonize artificial substrates in imitation of the
underface of stones.Helobdella stagnalis, Erpobdella octoculata andGlossiphonia complanata form the major part of collected fauna. Density fluctuations, population structures (age groups) and quantitative relations
between these three species as well as their vertical and horizontal distribution patterns were examined in great detail.
相似文献
77.
Wen-Feng Luo Jun Yang Lang Cui Xiang Liu Zhi-Qiang Shen 《中国天文和天体物理学报》2007,7(5):611-619
We present quasi-simultaneous VLBI images of the GHz-Peaked-Spectrum radio source OQ 208 obtained with the Very Long Baseline Array at 1.4,1.7,2.3,5.0,8.4,15.4GHz and the European VLBI Network at 6.7 GHz.The low frequency(1.4,1.7 and 2.3GHz)ob- servations reveal a weak and extended steep-spectrum component at about 30mas away at position angle-110°,which may be a remnant emission.The radio structure of OQ 208 con- sists of two mini-lobes at 5.0,6.7,8.4 and 15.4 GHz.Our spectral analysis further confirms that the southwest lobe undergoes free-free absorption and finds that the free-free absorption is stronger in the inner region.By fitting the 8.4 GHz images from 1994 to 2005,we obtain a separation speed of 0.031±0.006 mas yr~(-1)between the two mini-lobes.This indicates a jet proper motion of 0.105±0.020 c and a kinematic age of 219±42 yr for the radio source. 相似文献
78.
利用NOAA-AVHRR数据分析1982-2001年间中国植被的动态变化(英文) 总被引:1,自引:0,他引:1
The authors derived the normalized difference vegetation index (NDVI) from the NOAA/AVHRR Land dataset, at a spatial resolution of 8km and 15-day intervals, to investigate the vegetation variations in China during the period from 1982 to 2001. Then, GIS is used to examine the relationship between precipitation and the Normalized Difference Vegetation Index (NDVI) in China, and the value of NDVI is taken as a tool for drought monitoring. The results showed that in the study period, China’s vegetation cover h... 相似文献
79.
In this paper, we apply lagged correlation analysis to study the effects of vegetation cover on the summer climate in different zones of China, using NOAA/AVHRR normalized difference vegetation index (NDVI) data during the time period from 1982 to 2001 and climate data of 365 meteorological stations across China (precipitation from 1982 to 2001 and temperature from 1982 to 1998). The results show that there are positive correlations between spring NDVI and summer climate (temperature and precipitation) in m... 相似文献
80.
Banana is one of the main economic agrotypes in Zhangzhou, Fujian Province. The multi-temporal ENVISAT ASAR data with different
polarization are used to classify the banana fields in this paper. Principal component analysis (PCA) was applied for six
pairs of ASAR dual-polarization data. For its large leaves, banana has high backscatter. So the value of banana fields is
high and shows very bright in the 1st component, which makes it much easier for banana fields extraction. Dual-polarization
data provide more information, and the VV and VH backscatter of banana show different characters with other land covers. Based
on the analysis of the radar signature of banana fields and other land covers and the 1st component, banana fields are classified
using object-oriented classifier. Compared to the field survey data and ASTER data, the accuracy of banana fields in the study
area is 83.5%. It shows that the principal component analysis provides the useful information in SAR images analysis and makes
the extraction of banana fields easier.
Supported by the Program for New Century Excellent Talents in University (NCET-05-0573), Fujian Science and Technology Project
(No.2006I0018), the Science Project of the Education Department of Fujian Province(No. 2006F5022). 相似文献